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  <meta content="width=device-width, initial-scale=1, shrink-to-fit=no" name="viewport">
  <title>P2374R2: views::cartesian_product</title>
<style data-fill-with="stylesheet">/******************************************************************************
 *                   Style sheet for the W3C specifications                   *
 *
 * Special classes handled by this style sheet include:
 *
 * Indices
 *   - .toc for the Table of Contents (<ol class="toc">)
 *     + <span class="secno"> for the section numbers
 *   - #toc for the Table of Contents (<nav id="toc">)
 *   - ul.index for Indices (<a href="#ref">term</a><span>, in §N.M</span>)
 *   - table.index for Index Tables (e.g. for properties or elements)
 *
 * Structural Markup
 *   - table.data for general data tables
 *     -> use 'scope' attribute, <colgroup>, <thead>, and <tbody> for best results !
 *     -> use <table class='complex data'> for extra-complex tables
 *     -> use <td class='long'> for paragraph-length cell content
 *     -> use <td class='pre'> when manual line breaks/indentation would help readability
 *   - dl.switch for switch statements
 *   - ol.algorithm for algorithms (helps to visualize nesting)
 *   - .figure and .caption (HTML4) and figure and figcaption (HTML5)
 *     -> .sidefigure for right-floated figures
 *   - ins/del
 *     -> ins/del.c### for candidate and proposed changes (amendments)
 *
 * Code
 *   - pre and code
 *
 * Special Sections
 *   - .note       for informative notes             (div, p, span, aside, details)
 *   - .example    for informative examples          (div, p, pre, span)
 *   - .issue      for issues                        (div, p, span)
 *   - .advisement for loud normative statements     (div, p, strong)
 *   - .annoying-warning for spec obsoletion notices (div, aside, details)
 *   - .correction for "candidate corrections"       (div, aside, details, section)
 *   - .addition   for "candidate additions"         (div, aside, details, section)
 *   - .correction.proposed for "proposed corrections" (div, aside, details, section)
 *   - .addition.proposed   for "proposed additions"   (div, aside, details, section)
 *
 * Definition Boxes
 *   - pre.def   for WebIDL definitions
 *   - table.def for tables that define other entities (e.g. CSS properties)
 *   - dl.def    for definition lists that define other entitles (e.g. HTML elements)
 *
 * Numbering
 *   - .secno for section numbers in .toc and headings (<span class='secno'>3.2</span>)
 *   - .marker for source-inserted example/figure/issue numbers (<span class='marker'>Issue 4</span>)
 *   - ::before styled for CSS-generated issue/example/figure numbers:
 *     -> Documents wishing to use this only need to add
 *        figcaption::before,
 *        .caption::before { content: "Figure "  counter(figure) " ";  }
 *        .example::before { content: "Example " counter(example) " "; }
 *        .issue::before   { content: "Issue "   counter(issue) " ";   }
 *
 * Header Stuff (ignore, just don't conflict with these classes)
 *   - .head for the header
 *   - .copyright for the copyright
 *
 * Outdated warning for old specs
 *
 * Miscellaneous
 *   - .overlarge for things that should be as wide as possible, even if
 *     that overflows the body text area. This can be used on an item or
 *     on its container, depending on the effect desired.
 *     Note that this styling basically doesn't help at all when printing,
 *     since A4 paper isn't much wider than the max-width here.
 *     It's better to design things to fit into a narrower measure if possible.
 *
 *   - js-added ToC jump links (see fixup.js)
 *
 ******************************************************************************/

/* color variables included separately for reliability */

/******************************************************************************/
/*                                    Body                                    */
/******************************************************************************/

	html {
	}

	body {
		counter-reset: example figure issue;

		/* Layout */
		max-width: 50em;			  /* limit line length to 50em for readability   */
		margin: 0 auto;				/* center text within page                    */
		padding: 1.6em 1.5em 2em 50px; /* assume 16px font size for downlevel clients */
		padding: 1.6em 1.5em 2em calc(26px + 1.5em); /* leave space for status flag    */

		/* Typography */
		line-height: 1.5;
		font-family: sans-serif;
		widows: 2;
		orphans: 2;
		word-wrap: break-word;
		overflow-wrap: break-word;
		hyphens: auto;

		color: black;
		color: var(--text);
		background: white top left fixed no-repeat;
		background: var(--bg) top left fixed no-repeat;
		background-size: 25px auto;
	}


/******************************************************************************/
/*                         Front Matter & Navigation                          */
/******************************************************************************/

/** Header ********************************************************************/

	div.head { margin-bottom: 1em; }
	div.head hr { border-style: solid; }

	div.head h1 {
		font-weight: bold;
		margin: 0 0 .1em;
		font-size: 220%;
	}

	div.head h2 { margin-bottom: 1.5em;}

/** W3C Logo ******************************************************************/

	.head .logo {
		float: right;
		margin: 0.4rem 0 0.2rem .4rem;
	}

	.head img[src*="logos/W3C"] {
		display: block;
		border: solid #1a5e9a;
		border: solid var(--logo-bg);
		border-width: .65rem .7rem .6rem;
		border-radius: .4rem;
		background: #1a5e9a;
		background: var(--logo-bg);
		color: white;
		color: var(--logo-text);
		font-weight: bold;
	}

	.head a:hover > img[src*="logos/W3C"],
	.head a:focus > img[src*="logos/W3C"] {
		opacity: .8;
	}

	.head a:active > img[src*="logos/W3C"] {
		background: #c00;
		background: var(--logo-active-bg);
		border-color: #c00;
		border-color: var(--logo-active-bg);
	}

	/* see also additional rules in Link Styling section */

/** Copyright *****************************************************************/

	p.copyright,
	p.copyright small { font-size: small; }

/** Back to Top / ToC Toggle **************************************************/

	@media print {
		#toc-nav {
			display: none;
		}
	}
	@media not print {
		#toc-nav {
			position: fixed;
			z-index: 3;
			bottom: 0; left: 0;
			margin: 0;
			min-width: 1.33em;
			border-top-right-radius: 2rem;
			box-shadow: 0 0 2px;
			font-size: 1.5em;
		}
		#toc-nav > a {
			display: block;
			white-space: nowrap;

			height: 1.33em;
			padding: .1em 0.3em;
			margin: 0;

			box-shadow: 0 0 2px;
			border: none;
			border-top-right-radius: 1.33em;

			color: #707070;
			color: var(--tocnav-normal-text);
			background: white;
			background: var(--tocnav-normal-bg);
		}
		#toc-nav > a:hover,
		#toc-nav > a:focus {
			color: black;
			color: var(--tocnav-hover-text);
			background: #f8f8f8;
			background: var(--tocnav-hover-bg);
		}
		#toc-nav > a:active {
			color: #c00;
			color: var(--tocnav-active-text);
			background: white;
			background: var(--tocnav-active-bg);
		}

		#toc-nav > #toc-jump {
			padding-bottom: 2em;
			margin-bottom: -1.9em;
		}

		/* statusbar gets in the way on keyboard focus; remove once browsers fix */
		#toc-nav > a[href="#toc"]:not(:hover):focus:last-child {
			padding-bottom: 1.5rem;
		}

		#toc-nav:not(:hover) > a:not(:focus) > span + span {
			/* Ideally this uses :focus-within on #toc-nav */
			display: none;
		}
		#toc-nav > a > span + span {
			padding-right: 0.2em;
		}
	}

/** ToC Sidebar ***************************************************************/

	/* Floating sidebar */
	@media screen {
		body.toc-sidebar #toc {
			position: fixed;
			top: 0; bottom: 0;
			left: 0;
			width: 23.5em;
			max-width: 80%;
			max-width: calc(100% - 2em - 26px);
			overflow: auto;
			padding: 0 1em;
			padding-left: 42px;
			padding-left: calc(1em + 26px);
			color: black;
			color: var(--tocsidebar-text);
			background: inherit;
			background-color: #f7f8f9;
			background-color: var(--tocsidebar-bg);
			z-index: 1;
			box-shadow: -.1em 0 .25em rgba(0,0,0,.1) inset;
			box-shadow: -.1em 0 .25em var(--tocsidebar-shadow) inset;
		}
		body.toc-sidebar #toc h2 {
			margin-top: .8rem;
			font-variant: small-caps;
			font-variant: all-small-caps;
			text-transform: lowercase;
			font-weight: bold;
			color: gray;
			color: hsla(203,20%,40%,.7);
			color: var(--tocsidebar-heading-text);
		}
		body.toc-sidebar #toc-jump:not(:focus) {
			width: 0;
			height: 0;
			padding: 0;
			position: absolute;
			overflow: hidden;
		}
	}
	/* Hide main scroller when only the ToC is visible anyway */
	@media screen and (max-width: 28em) {
		body.toc-sidebar {
			overflow: hidden;
		}
	}

	/* Sidebar with its own space */
	@media screen and (min-width: 78em) {
		body:not(.toc-inline) #toc {
			position: fixed;
			top: 0; bottom: 0;
			left: 0;
			width: 23.5em;
			overflow: auto;
			padding: 0 1em;
			padding-left: 42px;
			padding-left: calc(1em + 26px);
			color: black;
			color: var(--tocsidebar-text);
			background: inherit;
			background-color: #f7f8f9;
			background-color: var(--tocsidebar-bg);
			z-index: 1;
			box-shadow: -.1em 0 .25em rgba(0,0,0,.1) inset;
			box-shadow: -.1em 0 .25em var(--tocsidebar-shadow) inset;
		}
		body:not(.toc-inline) #toc h2 {
			margin-top: .8rem;
			font-variant: small-caps;
			font-variant: all-small-caps;
			text-transform: lowercase;
			font-weight: bold;
			color: gray;
			color: hsla(203,20%,40%,.7);
			color: var(--tocsidebar-heading-text);
		}

		body:not(.toc-inline) {
			padding-left: 29em;
		}
		/* See also Overflow section at the bottom */

		body:not(.toc-inline) #toc-jump:not(:focus) {
			width: 0;
			height: 0;
			padding: 0;
			position: absolute;
			overflow: hidden;
		}
	}
	@media screen and (min-width: 90em) {
		body:not(.toc-inline) {
			margin: 0 4em;
		}
	}

/******************************************************************************/
/*                                Sectioning                                  */
/******************************************************************************/

/** Headings ******************************************************************/

	h1, h2, h3, h4, h5, h6, dt {
		page-break-after: avoid;
		page-break-inside: avoid;
		font: 100% sans-serif;   /* Reset all font styling to clear out UA styles */
		font-family: inherit;	/* Inherit the font family. */
		line-height: 1.2;		/* Keep wrapped headings compact */
		hyphens: manual;		/* Hyphenated headings look weird */
	}

	h2, h3, h4, h5, h6 {
		margin-top: 3rem;
	}

	h1, h2, h3 {
		color: #005A9C;
		color: var(--heading-text);
	}

	h1 { font-size: 170%; }
	h2 { font-size: 140%; }
	h3 { font-size: 120%; }
	h4 { font-weight: bold; }
	h5 { font-style: italic; }
	h6 { font-variant: small-caps; }
	dt { font-weight: bold; }

/** Subheadings ***************************************************************/

	h1 + h2,
	#subtitle {
		/* #subtitle is a subtitle in an H2 under the H1 */
		margin-top: 0;
	}
	h2 + h3,
	h3 + h4,
	h4 + h5,
	h5 + h6 {
		margin-top: 1.2em; /* = 1 x line-height */
	}

/** Section divider ***********************************************************/

	:not(.head) > :not(.head) + hr {
		font-size: 1.5em;
		text-align: center;
		margin: 1em auto;
		height: auto;
		color: black;
		color: var(--hr-text);
		border: transparent solid 0;
		background: transparent;
	}
	:not(.head) > hr::before {
		content: "\2727\2003\2003\2727\2003\2003\2727";
	}

/******************************************************************************/
/*                            Paragraphs and Lists                            */
/******************************************************************************/

	p {
		margin: 1em 0;
	}

	dd > p:first-child,
	li > p:first-child {
		margin-top: 0;
	}

	ul, ol {
		margin-left: 0;
		padding-left: 2em;
	}

	li {
		margin: 0.25em 0 0.5em;
		padding: 0;
	}

	dl dd {
		margin: 0 0 .5em 2em;
	}

	.head dd + dd { /* compact for header */
		margin-top: -.5em;
	}

	/* Style for algorithms */
	ol.algorithm ol:not(.algorithm),
	.algorithm > ol ol:not(.algorithm) {
	border-left: 0.5em solid #DEF;
	border-left: 0.5em solid var(--algo-border);
	}

	/* Put nice boxes around each algorithm. */
	[data-algorithm]:not(.heading) {
	 padding: .5em;
	 border: thin solid #ddd;
	 border: thin solid var(--algo-border);
	 border-radius: .5em;
	 margin: .5em calc(-0.5em - 1px);
	}
	[data-algorithm]:not(.heading) > :first-child {
	 margin-top: 0;
	}
	[data-algorithm]:not(.heading) > :last-child {
	 margin-bottom: 0;
	}

	/* Style for switch/case <dl>s */
	dl.switch > dd > ol.only,
	dl.switch > dd > .only > ol {
	margin-left: 0;
	}
	dl.switch > dd > ol.algorithm,
	dl.switch > dd > .algorithm > ol {
	margin-left: -2em;
	}
	dl.switch {
	padding-left: 2em;
	}
	dl.switch > dt {
	text-indent: -1.5em;
	margin-top: 1em;
	}
	dl.switch > dt + dt {
	margin-top: 0;
	}
	dl.switch > dt::before {
	content: '\21AA';
	padding: 0 0.5em 0 0;
	display: inline-block;
	width: 1em;
	text-align: right;
	line-height: 0.5em;
	}

/** Terminology Markup ********************************************************/


/******************************************************************************/
/*                                 Inline Markup                              */
/******************************************************************************/

/** Terminology Markup ********************************************************/
	dfn   { /* Defining instance */
		font-weight: bolder;
	}
	a > i { /* Instance of term */
		font-style: normal;
	}
	dt dfn code, code.idl {
		font-size: inherit;
	}
	dfn var {
		font-style: normal;
	}

/** Change Marking ************************************************************/

	del {
		color: #aa0000;
		color: var(--del-text);
		background: transparent;
		background: var(--del-bg);
		text-decoration: line-through;
	}
	ins {
		color: #006100;
		color: var(--ins-text);
		background: transparent;
		background: var(--ins-bg);
		text-decoration: underline;
	}

	/* for amendments (candidate/proposed changes) */

	.amendment ins, .correction ins, .addition ins,
	ins[class^=c] {
		text-decoration-style: dotted;
	}
	.amendment del, .correction del, .addition del,
	del[class^=c] {
		text-decoration-style: dotted;
	}
	.amendment.proposed ins, .correction.proposed ins, .addition.proposed ins,
	ins[class^=c].proposed {
		text-decoration-style: double;
	}
	.amendment.proposed del, .correction.proposed del, .addition.proposed del,
	del[class^=c].proposed {
		text-decoration-style: double;
	}

/** Miscellaneous improvements to inline formatting ***************************/

	sup {
		vertical-align: super;
		font-size: 80%
	}

/******************************************************************************/
/*                                    Code                                    */
/******************************************************************************/

/** General monospace/pre rules ***********************************************/

	pre, code, samp {
		font-family: Menlo, Consolas, "DejaVu Sans Mono", Monaco, monospace;
		font-size: .9em;
		hyphens: none;
		text-transform: none;
		text-align: left;
		text-align: start;
		font-variant: normal;
		orphans: 3;
		widows: 3;
		page-break-before: avoid;
	}
	pre code,
	code code {
		font-size: 100%;
	}

	pre {
		margin-top: 1em;
		margin-bottom: 1em;
		overflow: auto;
	}

/** Inline Code fragments *****************************************************/

	/* Do something nice. */

/******************************************************************************/
/*                                    Links                                   */
/******************************************************************************/

/** General Hyperlinks ********************************************************/

	/* We hyperlink a lot, so make it less intrusive */
	a[href] {
		color: #034575;
		color: var(--a-normal-text);
		text-decoration: none;
		border-bottom: 1px solid #707070;
		border-bottom: 1px solid var(--a-normal-underline);
		/* Need a bit of extending for it to look okay */
		padding: 0 1px 0;
		margin: 0 -1px 0;
	}
	a:visited {
		color: #034575;
		color: var(--a-visited-text);
		border-bottom-color: #bbb;
		border-bottom-color: var(--a-visited-underline);
	}

	/* Use distinguishing colors when user is interacting with the link */
	a[href]:focus,
	a[href]:hover {
		background: #f8f8f8;
		background: rgba(75%, 75%, 75%, .25);
		background: var(--a-hover-bg);
		border-bottom-width: 3px;
		margin-bottom: -2px;
	}
	a[href]:active {
		color: #c00;
		color: var(--a-active-text);
		border-color: #c00;
		border-color: var(--a-active-underline);
	}

	/* Backout above styling for W3C logo */
	.head .logo,
	.head .logo a {
		border: none;
		text-decoration: none;
		background: transparent;
	}

/******************************************************************************/
/*                                    Images                                  */
/******************************************************************************/

	img {
		border-style: none;
	}

	img, svg {
		/* Intentionally not color-scheme aware. */
		background: white;
	}

	/* For autogen numbers, add
	  .caption::before, figcaption::before { content: "Figure " counter(figure) ". "; }
	*/

	figure, .figure, .sidefigure {
		page-break-inside: avoid;
		text-align: center;
		margin: 2.5em 0;
	}
	.figure img,	.sidefigure img,	figure img,
	.figure object, .sidefigure object, figure object {
		max-width: 100%;
		margin: auto;
		height: auto;
	}
	.figure pre, .sidefigure pre, figure pre {
		text-align: left;
		display: table;
		margin: 1em auto;
	}
	.figure table, figure table {
		margin: auto;
	}
	@media screen and (min-width: 20em) {
		.sidefigure {
			float: right;
			width: 50%;
			margin: 0 0 0.5em 0.5em;
		}
	}
	.caption, figcaption, caption {
		font-style: italic;
		font-size: 90%;
	}
	.caption::before, figcaption::before, figcaption > .marker {
		font-weight: bold;
	}
	.caption, figcaption {
		counter-increment: figure;
	}

	/* DL list is indented 2em, but figure inside it is not */
	dd > .figure, dd > figure { margin-left: -2em; }

/******************************************************************************/
/*                             Colored Boxes                                  */
/******************************************************************************/

	.issue, .note, .example, .assertion, .advisement, blockquote,
	.amendment, .correction, .addition {
		margin: 1em auto;
		padding: .5em;
		border: .5em;
		border-left-style: solid;
		page-break-inside: avoid;
	}
	span.issue, span.note {
		padding: .1em .5em .15em;
		border-right-style: solid;
	}

	blockquote > :first-child,
	.note  > p:first-child,
	.issue > p:first-child,
	.amendment > p:first-child,
	.correction > p:first-child,
	.addition > p:first-child {
		margin-top: 0;
	}
	blockquote > :last-child,
	.note  > p:last-child,
	.issue > p:last-child,
	.amendment > p:last-child,
	.correction > p:last-child,
	.addition > p:last-child {
		margin-bottom: 0;
	}


	.issue::before, .issue > .marker,
	.example::before, .example > .marker,
	.note::before, .note > .marker,
	details.note > summary > .marker,
	.amendment::before, .amendment > .marker,
	details.amendment > summary > .marker,
	.addition::before, .addition > .marker,
	addition.amendment > summary > .marker,
	.correction::before, .correction > .marker,
	correction.amendment > summary > .marker
	{
		text-transform: uppercase;
		padding-right: 1em;
	}

	.example::before, .example > .marker {
		display: block;
		padding-right: 0em;
	}

/** Blockquotes ***************************************************************/

	blockquote {
		border-color: silver;
		border-color: var(--blockquote-border);
		background: transparent;
		background: var(--blockquote-bg);
		color: currentcolor;
		color: var(--blockquote-text);
	}

/** Open issue ****************************************************************/

	.issue {
		border-color: #e05252;
		border-color: var(--issue-border);
		background: #fbe9e9;
		background: var(--issue-bg);
		color: black;
		color: var(--issue-text);
		counter-increment: issue;
		overflow: auto;
	}
	.issue::before, .issue > .marker {
		color: #831616;
		color: var(--issueheading-text);
	}
	/* Add .issue::before { content: "Issue " counter(issue) " "; } for autogen numbers,
	  or use class="marker" to mark up the issue number in source. */

/** Example *******************************************************************/

	.example {
		border-color: #e0cb52;
		border-color: var(--example-border);
		background: #fcfaee;
		background: var(--example-bg);
		color: black;
		color: var(--example-text);
		counter-increment: example;
		overflow: auto;
		clear: both;
	}
	.example::before, .example > .marker {
		color: #574b0f;
		color: var(--exampleheading-text);
	}
	/* Add .example::before { content: "Example " counter(example) " "; } for autogen numbers,
	  or use class="marker" to mark up the example number in source. */

/** Non-normative Note ********************************************************/

	.note {
		border-color: #52e052;
		border-color: var(--note-border);
		background: #e9fbe9;
		background: var(--note-bg);
		color: black;
		color: var(--note-text);
		overflow: auto;
	}

	.note::before, .note > .marker,
	details.note > summary {
		color: hsl(120, 70%, 30%);
		color: var(--noteheading-text);
	}
	/* Add .note::before { content: "Note "; } for autogen label,
	  or use class="marker" to mark up the label in source. */

	details.note[open] > summary {
		border-bottom: 1px silver solid;
		border-bottom: 1px var(--notesummary-underline) solid;
	}

/** Assertion Box *************************************************************/
	/*  for assertions in algorithms */

	.assertion {
		border-color: #AAA;
		border-color: var(--assertion-border);
		background: #EEE;
		background: var(--assertion-bg);
		color: black;
		color: var(--assertion-text);
	}

/** Advisement Box ************************************************************/
	/*  for attention-grabbing normative statements */

	.advisement {
		border-color: orange;
		border-color: var(--advisement-border);
		border-style: none solid;
		background: #fec;
		background: var(--advisement-bg);
		color: black;
		color: var(--advisement-text);
	}
	strong.advisement {
		display: block;
		text-align: center;
	}
	.advisement::before, .advisement > .marker {
		color: #b35f00;
		color: var(--advisementheading-text);
	}

/** Amendment Box *************************************************************/

	.amendment, .correction, .addition {
		border-color: #330099;
		border-color: var(--amendment-border);
		background: #F5F0FF;
		background: var(--amendment-bg);
		color: black;
		color: var(--amendment-text);
	}
	.amendment.proposed, .correction.proposed, .addition.proposed {
		border-style: solid;
		border-block-width: 0.25em;
	}
	.amendment::before, .amendment > .marker,
	details.amendment > summary::before, details.amendment > summary > .marker,
	.correction::before, .correction > .marker,
	details.correction > summary::before, details.correction > summary > .marker,
	.addition::before, .addition > .marker,
	details.addition > summary::before, details.addition > summary > .marker {
		color: #220066;
		color: var(--amendmentheading-text);
	}
	.amendment.proposed::before, .amendment.proposed > .marker,
	details.amendment.proposed > summary::before, details.amendment.proposed > summary > .marker,
	.correction.proposed::before, .correction.proposed > .marker,
	details.correction.proposed > summary::before, details.correction.proposed > summary > .marker,
	.addition.proposed::before, .addition.proposed > .marker,
	details.addition.proposed > summary::before, details.addition.proposed > summary > .marker {
		font-weight: bold;
	}

/** Spec Obsoletion Notice ****************************************************/
	/* obnoxious obsoletion notice for older/abandoned specs. */

	details {
		display: block;
	}
	summary {
		font-weight: bolder;
	}

	.annoying-warning:not(details),
	details.annoying-warning:not([open]) > summary,
	details.annoying-warning[open] {
		background: hsla(40,100%,50%,0.95);
		background: var(--warning-bg);
		color: black;
		color: var(--warning-text);
		padding: .75em 1em;
		border: red;
		border: var(--warning-border);
		border-style: solid none;
		box-shadow: 0 2px 8px black;
		text-align: center;
	}
	.annoying-warning :last-child {
		margin-bottom: 0;
	}

@media not print {
	details.annoying-warning[open] {
		position: fixed;
		left: 0;
		right: 0;
		bottom: 2em;
		z-index: 1000;
	}
}

	details.annoying-warning:not([open]) > summary {
		text-align: center;
	}

/** Entity Definition Boxes ***************************************************/

	.def {
		padding: .5em 1em;
		background: #def;
		background: var(--def-bg);
		margin: 1.2em 0;
		border-left: 0.5em solid #8ccbf2;
		border-left: 0.5em solid var(--def-border);
		color: black;
		color: var(--def-text);
	}

/******************************************************************************/
/*                                    Tables                                  */
/******************************************************************************/

	th, td {
		text-align: left;
		text-align: start;
	}

/** Property/Descriptor Definition Tables *************************************/

	table.def {
		/* inherits .def box styling, see above */
		width: 100%;
		border-spacing: 0;
	}

	table.def td,
	table.def th {
		padding: 0.5em;
		vertical-align: baseline;
		border-bottom: 1px solid #bbd7e9;
		border-bottom: 1px solid var(--defrow-border);
	}

	table.def > tbody > tr:last-child th,
	table.def > tbody > tr:last-child td {
		border-bottom: 0;
	}

	table.def th {
		font-style: italic;
		font-weight: normal;
		padding-left: 1em;
		width: 3em;
	}

	/* For when values are extra-complex and need formatting for readability */
	table td.pre {
		white-space: pre-wrap;
	}

	/* A footnote at the bottom of a def table */
	table.def td.footnote {
		padding-top: 0.6em;
	}
	table.def td.footnote::before {
		content: " ";
		display: block;
		height: 0.6em;
		width: 4em;
		border-top: thin solid;
	}

/** Data tables (and properly marked-up index tables) *************************/
	/*
		<table class="data"> highlights structural relationships in a table
		when correct markup is used (e.g. thead/tbody, th vs. td, scope attribute)

		Use class="complex data" for particularly complicated tables --
		(This will draw more lines: busier, but clearer.)

		Use class="long" on table cells with paragraph-like contents
		(This will adjust text alignment accordingly.)
		Alternately use class="longlastcol" on tables, to have the last column assume "long".
	*/

	table {
		word-wrap: normal;
		overflow-wrap: normal;
		hyphens: manual;
	}

	table.data,
	table.index {
		margin: 1em auto;
		border-collapse: collapse;
		border: hidden;
		width: 100%;
	}
	table.data caption,
	table.index caption {
		max-width: 50em;
		margin: 0 auto 1em;
	}

	table.data td,  table.data th,
	table.index td, table.index th {
		padding: 0.5em 1em;
		border-width: 1px;
		border-color: silver;
		border-color: var(--datacell-border);
		border-top-style: solid;
	}

	table.data thead td:empty {
		padding: 0;
		border: 0;
	}

	table.data  thead,
	table.index thead,
	table.data  tbody,
	table.index tbody {
		border-bottom: 2px solid;
	}

	table.data colgroup,
	table.index colgroup {
		border-left: 2px solid;
	}

	table.data  tbody th:first-child,
	table.index tbody th:first-child  {
		border-right: 2px solid;
		border-top: 1px solid silver;
		border-top: 1px solid var(--datacell-border);
		padding-right: 1em;
	}

	table.data th[colspan],
	table.data td[colspan] {
		text-align: center;
	}

	table.complex.data th,
	table.complex.data td {
		border: 1px solid silver;
		border: 1px solid var(--datacell-border);
		text-align: center;
	}

	table.data.longlastcol td:last-child,
	table.data td.long {
		vertical-align: baseline;
		text-align: left;
	}

	table.data img {
		vertical-align: middle;
	}


/*
Alternate table alignment rules

	table.data,
	table.index {
		text-align: center;
	}

	table.data  thead th[scope="row"],
	table.index thead th[scope="row"] {
		text-align: right;
	}

	table.data  tbody th:first-child,
	table.index tbody th:first-child  {
		text-align: right;
	}

Possible extra rowspan handling

	table.data  tbody th[rowspan]:not([rowspan='1']),
	table.index tbody th[rowspan]:not([rowspan='1']),
	table.data  tbody td[rowspan]:not([rowspan='1']),
	table.index tbody td[rowspan]:not([rowspan='1']) {
		border-left: 1px solid silver;
	}

	table.data  tbody th[rowspan]:first-child,
	table.index tbody th[rowspan]:first-child,
	table.data  tbody td[rowspan]:first-child,
	table.index tbody td[rowspan]:first-child{
		border-left: 0;
		border-right: 1px solid silver;
	}
*/

/******************************************************************************/
/*                                  Indices                                   */
/******************************************************************************/


/** Table of Contents *********************************************************/

	.toc a {
		/* More spacing; use padding to make it part of the click target. */
		padding-top: 0.1rem;
		/* Larger, more consistently-sized click target */
		display: block;
		/* Reverse color scheme */
		color: black;
		color: var(--toclink-text);
		border-color: #3980b5;
		border-color: var(--toclink-underline);
	}
	.toc a:visited {
		color: black;
		color: var(--toclink-visited-text);
		border-color: #054572;
		border-color: var(--toclink-visited-underline);
	}
	.toc a:not(:focus):not(:hover) {
		/* Allow colors to cascade through from link styling */
		border-bottom-color: transparent;
	}

	.toc, .toc ol, .toc ul, .toc li {
		list-style: none; /* Numbers must be inlined into source */
		/* because generated content isn't search/selectable and markers can't do multilevel yet */
		margin:  0;
		padding: 0;
	}
	.toc {
		line-height: 1.1em;
	}

	/* ToC not indented until third level, but font style & margins show hierarchy */
	.toc > li			{ font-weight: bold;   }
	.toc > li li		 { font-weight: normal; }
	.toc > li li li	  { font-size:   95%;	}
	.toc > li li li li	{ font-size:   90%;	}
	.toc > li li li li li { font-size:   85%;	}

	/* @supports not (display:grid) { */
		.toc > li			{ margin: 1.5rem 0;	}
		.toc > li li		 { margin: 0.3rem 0;	}
		.toc > li li li	  { margin-left: 2rem;   }

		/* Section numbers in a column of their own */
		.toc .secno {
			float: left;
			width: 4rem;
			white-space: nowrap;
		}
		.toc > li li li li .secno { font-size: 85%; }
		.toc > li li li li li .secno { font-size: 100%; }

		.toc li {
			clear: both;
		}

		:not(li) > .toc			 { margin-left:  5rem; }
		.toc .secno				 { margin-left: -5rem; }
		.toc > li li li .secno	  { margin-left: -7rem; }
		.toc > li li li li .secno	{ margin-left: -9rem; }
		.toc > li li li li li .secno { margin-left: -11rem; }

		/* Tighten up indentation in narrow ToCs */
		@media (max-width: 30em) {
			:not(li) > .toc			 { margin-left:  4rem; }
			.toc .secno				 { margin-left: -4rem; }
			.toc > li li li			 { margin-left:  1rem; }
			.toc > li li li .secno	  { margin-left: -5rem; }
			.toc > li li li li .secno	{ margin-left: -6rem; }
			.toc > li li li li li .secno { margin-left: -7rem; }
		}
		/* Loosen it on wide screens */
		@media screen and (min-width: 78em) {
			body:not(.toc-inline) :not(li) > .toc			 { margin-left:  4rem; }
			body:not(.toc-inline) .toc .secno				 { margin-left: -4rem; }
			body:not(.toc-inline) .toc > li li li			 { margin-left:  1rem; }
			body:not(.toc-inline) .toc > li li li .secno	  { margin-left: -5rem; }
			body:not(.toc-inline) .toc > li li li li .secno	{ margin-left: -6rem; }
			body:not(.toc-inline) .toc > li li li li li .secno { margin-left: -7rem; }
	}
	/* } */

	@supports (display:grid) and (display:contents) {
		/* Use #toc over .toc to override non-@supports rules. */
		#toc {
			display: grid;
			align-content: start;
			grid-template-columns: auto 1fr;
			grid-column-gap: 1rem;
			column-gap: 1rem;
			grid-row-gap: .6rem;
			row-gap: .6rem;
		}
		#toc h2 {
			grid-column: 1 / -1;
			margin-bottom: 0;
		}
		#toc ol,
		#toc li,
		#toc a {
			display: contents;
			/* Switch <a> to subgrid when supported */
		}
		#toc span {
			margin: 0;
		}
		#toc > .toc > li > a > span {
			/* The spans of the top-level list,
			  comprising the first items of each top-level section. */
			margin-top: 1.1rem;
		}
		#toc#toc .secno { /* Ugh, need more specificity to override base.css */
			grid-column: 1;
			width: auto;
			margin-left: 0;
		}
		#toc .content {
			grid-column: 2;
			width: auto;
			margin-right: 1rem;
		}
		#toc .content:hover,
		#toc .content:focus {
			background: rgba(75%, 75%, 75%, .25);
			background: var(--a-hover-bg);
			border-bottom: 3px solid #054572;
			border-bottom: 3px solid var(--toclink-underline);
			margin-bottom: -3px;
		}
		#toc li li li .content {
			margin-left: 1rem;
		}
		#toc li li li li .content {
			margin-left: 2rem;
		}
	}


/** Index *********************************************************************/

	/* Index Lists: Layout */
	ul.index	  { margin-left: 0; columns: 15em; text-indent: 1em hanging; }
	ul.index li	{ margin-left: 0; list-style: none; break-inside: avoid; }
	ul.index li li { margin-left: 1em; }
	ul.index dl	{ margin-top: 0; }
	ul.index dt	{ margin: .2em 0 .2em 20px;}
	ul.index dd	{ margin: .2em 0 .2em 40px;}
	/* Index Lists: Typography */
	ul.index ul,
	ul.index dl { font-size: smaller; }
	@media not print {
		ul.index li span:not(.dfn-paneled) {
			white-space: nowrap;
			color: transparent; }
		ul.index li a:hover + span,
		ul.index li a:focus + span {
			color: #707070;
			color: var(--indexinfo-text);
		}
	}

/** Index Tables *****************************************************/
	/* See also the data table styling section, which this effectively subclasses */

	table.index {
		font-size: small;
		border-collapse: collapse;
		border-spacing: 0;
		text-align: left;
		margin: 1em 0;
	}

	table.index td,
	table.index th {
		padding: 0.4em;
	}

	table.index tr:hover td:not([rowspan]),
	table.index tr:hover th:not([rowspan]) {
		color: black;
		color: var(--indextable-hover-text);
		background: #f7f8f9;
		background: var(--indextable-hover-bg);
	}

	/* The link in the first column in the property table (formerly a TD) */
	table.index th:first-child a {
		font-weight: bold;
	}

/** Outdated warning **********************************************************/

.outdated-spec {
	color: black;
	color: var(--outdatedspec-text);
	background-color: rgba(0,0,0,0.5);
	background-color: var(--outdatedspec-bg);
}

.outdated-warning {
	position: fixed;
	bottom: 50%;
	left: 0;
	right: 0;
	margin: 0 auto;
	width: 50%;
	background: maroon;
	background: var(--outdated-bg);
	color: white;
	color: var(--outdated-text);
	border-radius: 1em;
	box-shadow: 0 0 1em red;
	box-shadow: 0 0 1em var(--outdated-shadow);
	padding: 2em;
	text-align: center;
	z-index: 2;
}

.outdated-warning a {
	color: currentcolor;
	background: transparent;
}

.edited-rec-warning {
	background: darkorange;
	background: var(--editedrec-bg);
	box-shadow: 0 0 1em;
}

.outdated-warning button {
	color: var(--outdated-text);
	border-radius: 1em;
	box-shadow: 0 0 1em red;
	box-shadow: 0 0 1em var(--outdated-shadow);
	padding: 2em;
	text-align: center;
	z-index: 2;
}

.outdated-warning a {
	color: currentcolor;
	background: transparent;
}

.edited-rec-warning {
	background: darkorange;
	background: var(--editedrec-bg);
	box-shadow: 0 0 1em;
}

.outdated-warning button {
	position: absolute;
	top: 0;
	right:0;
	margin: 0;
	border: 0;
	padding: 0.25em 0.5em;
	background: transparent;
	color: white;
	color: var(--outdated-text);
	font:1em sans-serif;
	text-align:center;
}

.outdated-warning span {
	display: block;
}

.outdated-collapsed {
	bottom: 0;
	border-radius: 0;
	width: 100%;
	padding: 0;
}

/******************************************************************************/
/*                                    Print                                   */
/******************************************************************************/

	@media print {
		/* Pages have their own margins. */
		html {
			margin: 0;
		}
		/* Serif for print. */
		body {
			font-family: serif;
		}

		.outdated-warning {
			position: absolute;
			border-style: solid;
			border-color: red;
		}

		.outdated-warning input {
			display: none;
		}
	}
	@page {
		margin: 1.5cm 1.1cm;
	}



/******************************************************************************/
/*                             Overflow Control                               */
/******************************************************************************/

	.figure .caption, .sidefigure .caption, figcaption {
		/* in case figure is overlarge, limit caption to 50em */
		max-width: 50rem;
		margin-left: auto;
		margin-right: auto;
	}
	.overlarge {
		/* Magic to create good item positioning:
		  "content column" is 50ems wide at max; less on smaller screens.
		  Extra space (after ToC + content) is empty on the right.

		  1. When item < content column, centers item in column.
		  2. When content < item < available, left-aligns.
		  3. When item > available, fills available + scroll bar.
		*/
		display: grid;
		grid-template-columns: minmax(0, 50em);
	}
	.overlarge > table {
		/* limit preferred width of table */
		max-width: 50em;
		margin-left: auto;
		margin-right: auto;
	}

	@media (min-width: 55em) {
		.overlarge {
			margin-right: calc(13px + 26.5rem - 50vw);
			max-width: none;
		}
	}
	@media screen and (min-width: 78em) {
		body:not(.toc-inline) .overlarge {
			/* 30.5em body padding 50em content area */
			margin-right: calc(40em - 50vw) !important;
		}
	}
	@media screen and (min-width: 90em) {
		body:not(.toc-inline) .overlarge {
			/* 4em html margin 30.5em body padding 50em content area */
			margin-right: calc(84.5em - 100vw) !important;
		}
	}

	@media not print {
		.overlarge {
			overflow-x: auto;
			/* See Lea Verou's explanation background-attachment:
			* http://lea.verou.me/2012/04/background-attachment-local/
			*
			background: top left  / 4em 100% linear-gradient(to right,  #ffffff, rgba(255, 255, 255, 0)) local,
						top right / 4em 100% linear-gradient(to left, #ffffff, rgba(255, 255, 255, 0)) local,
						top left  / 1em 100% linear-gradient(to right,  #c3c3c5, rgba(195, 195, 197, 0)) scroll,
						top right / 1em 100% linear-gradient(to left, #c3c3c5, rgba(195, 195, 197, 0)) scroll,
						white;
			background-repeat: no-repeat;
			*/
		}
	}
</style>
<style type="text/css">
    table, th, td {
      border: 1px solid black;
      border-collapse: collapse;
      vertical-align: top;
    }
    th, td {
      border-left: none;
      border-right: none;
      padding: 0px 10px;
    }
    th {
      text-align: center;
    }

    del { background: #fcc; color: #000; text-decoration: line-through; }
    ins { background: #cfc; color: #000; }
    blockquote .highlight:not(.idl) { background: initial; margin: initial; padding: 0.5em }
    blockquote ul { background: inherit; }
    blockquote code.highlight:not(.idl) { padding: initial; }
    blockquote c-[a] { color: inherit; } /* Keyword.Declaration */
    blockquote c-[b] { color: inherit; } /* Keyword.Type */
    blockquote c-[c] { color: inherit; } /* Comment */
    blockquote c-[d] { color: inherit; } /* Comment.Multiline */
    blockquote c-[e] { color: inherit; } /* Name.Attribute */
    blockquote c-[f] { color: inherit; } /* Name.Tag */
    blockquote c-[g] { color: inherit; } /* Name.Variable */
    blockquote c-[k] { color: inherit; } /* Keyword */
    blockquote c-[l] { color: inherit; } /* Literal */
    blockquote c-[m] { color: inherit; } /* Literal.Number */
    blockquote c-[n] { color: inherit; } /* Name */
    blockquote c-[o] { color: inherit; } /* Operator */
    blockquote c-[p] { color: inherit; } /* Punctuation */
    blockquote c-[s] { color: inherit; } /* Literal.String */
    blockquote c-[t] { color: inherit; } /* Literal.String.Single */
    blockquote c-[u] { color: inherit; } /* Literal.String.Double */
    blockquote c-[cp] { color: inherit; } /* Comment.Preproc */
    blockquote c-[c1] { color: inherit; } /* Comment.Single */
    blockquote c-[cs] { color: inherit; } /* Comment.Special */
    blockquote c-[kc] { color: inherit; } /* Keyword.Constant */
    blockquote c-[kn] { color: inherit; } /* Keyword.Namespace */
    blockquote c-[kp] { color: inherit; } /* Keyword.Pseudo */
    blockquote c-[kr] { color: inherit; } /* Keyword.Reserved */
    blockquote c-[ld] { color: inherit; } /* Literal.Date */
    blockquote c-[nc] { color: inherit; } /* Name.Class */
    blockquote c-[no] { color: inherit; } /* Name.Constant */
    blockquote c-[nd] { color: inherit; } /* Name.Decorator */
    blockquote c-[ni] { color: inherit; } /* Name.Entity */
    blockquote c-[ne] { color: inherit; } /* Name.Exception */
    blockquote c-[nf] { color: inherit; } /* Name.Function */
    blockquote c-[nl] { color: inherit; } /* Name.Label */
    blockquote c-[nn] { color: inherit; } /* Name.Namespace */
    blockquote c-[py] { color: inherit; } /* Name.Property */
    blockquote c-[ow] { color: inherit; } /* Operator.Word */
    blockquote c-[mb] { color: inherit; } /* Literal.Number.Bin */
    blockquote c-[mf] { color: inherit; } /* Literal.Number.Float */
    blockquote c-[mh] { color: inherit; } /* Literal.Number.Hex */
    blockquote c-[mi] { color: inherit; } /* Literal.Number.Integer */
    blockquote c-[mo] { color: inherit; } /* Literal.Number.Oct */
    blockquote c-[sb] { color: inherit; } /* Literal.String.Backtick */
    blockquote c-[sc] { color: inherit; } /* Literal.String.Char */
    blockquote c-[sd] { color: inherit; } /* Literal.String.Doc */
    blockquote c-[se] { color: inherit; } /* Literal.String.Escape */
    blockquote c-[sh] { color: inherit; } /* Literal.String.Heredoc */
    blockquote c-[si] { color: inherit; } /* Literal.String.Interpol */
    blockquote c-[sx] { color: inherit; } /* Literal.String.Other */
    blockquote c-[sr] { color: inherit; } /* Literal.String.Regex */
    blockquote c-[ss] { color: inherit; } /* Literal.String.Symbol */
    blockquote c-[vc] { color: inherit; } /* Name.Variable.Class */
    blockquote c-[vg] { color: inherit; } /* Name.Variable.Global */
    blockquote c-[vi] { color: inherit; } /* Name.Variable.Instance */
    blockquote c-[il] { color: inherit; } /* Literal.Number.Integer.Long */
  </style>
  <meta content="Bikeshed version c5172e83, updated Fri Nov 20 15:35:20 2020 -0800" name="generator">
  <link href="http://wg21.link/P2374" rel="canonical">
  <link href="https://isocpp.org/favicon.ico" rel="icon">
<style>/* style-autolinks */

.css.css, .property.property, .descriptor.descriptor {
    color: var(--a-normal-text);
    font-size: inherit;
    font-family: inherit;
}
.css::before, .property::before, .descriptor::before {
    content: "‘";
}
.css::after, .property::after, .descriptor::after {
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  <div class="head">
   <p data-fill-with="logo"></p>
   <h1 class="p-name no-ref" id="title">P2374R2<br>views::cartesian_product</h1>
   <h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="content">Published Proposal, <time class="dt-updated" datetime="2021-11-04">2021-11-04</time></span></h2>
   <div data-fill-with="spec-metadata">
    <dl>
     <dt>This version:
     <dd><a class="u-url" href="http://wg21.link/P2374">http://wg21.link/P2374</a>
     <dt class="editor">Authors:
     <dd class="editor p-author h-card vcard"><span class="p-name fn">Sy Brand</span> (<span class="p-org org">sy.brand at microsoft dot com</span>)
     <dd class="editor p-author h-card vcard"><span class="p-name fn">Michał Dominiak</span> (<span class="p-org org">griwes at griwes dot info</span>)
     <dt>Audience:
     <dd>LEWG
     <dt>Project:
     <dd>ISO/IEC JTC1/SC22/WG21 14882: Programming Language — C++
    </dl>
   </div>
   <div data-fill-with="warning"></div>
   <hr title="Separator for header">
  </div>
  <div class="p-summary" data-fill-with="abstract">
   <h2 class="no-num no-toc no-ref heading settled" id="abstract"><span class="content">Abstract</span></h2>
   <p>This paper proposes std::ranges::cartesian_product_view for taking the cartesian product of multiple forward ranges.</p>
  </div>
  <nav data-fill-with="table-of-contents" id="toc">
   <h2 class="no-num no-toc no-ref" id="contents">Table of Contents</h2>
   <ol class="toc" role="directory">
    <li>
     <a href="#changelog"><span class="secno">1</span> <span class="content">Changelog</span></a>
     <ol class="toc">
      <li><a href="#changes-from-r1"><span class="secno">1.1</span> <span class="content">Changes from r1</span></a>
      <li><a href="#changes-from-r0"><span class="secno">1.2</span> <span class="content">Changes from r0</span></a>
     </ol>
    <li><a href="#motivation"><span class="secno">2</span> <span class="content">Motivation</span></a>
    <li>
     <a href="#design"><span class="secno">3</span> <span class="content">Design</span></a>
     <ol class="toc">
      <li><a href="#minimum-range-requirements"><span class="secno">3.1</span> <span class="content">Minimum Range Requirements</span></a>
      <li><a href="#tuple-or-pair"><span class="secno">3.2</span> <span class="content">Tuple or pair</span></a>
      <li><a href="#reference_type"><span class="secno">3.3</span> <span class="content"><code class="highlight"><c- n>reference_type</c-></code></span></a>
      <li><a href="#empty-cartesian-product-view"><span class="secno">3.4</span> <span class="content">Empty cartesian product view</span></a>
      <li><a href="#common-range"><span class="secno">3.5</span> <span class="content">Common Range</span></a>
      <li><a href="#bidirectional-range"><span class="secno">3.6</span> <span class="content">Bidirectional Range</span></a>
      <li><a href="#random-access-range"><span class="secno">3.7</span> <span class="content">Random Access Range</span></a>
      <li><a href="#initialrange"><span class="secno">3.8</span> <span class="content">Initial Range Argument Special-Casing</span></a>
      <li><a href="#sized-range"><span class="secno">3.9</span> <span class="content">Sized Range</span></a>
      <li><a href="#naming"><span class="secno">3.10</span> <span class="content">Naming</span></a>
      <li><a href="#pipe-support"><span class="secno">3.11</span> <span class="content">Pipe Support</span></a>
      <li><a href="#borrowed-range"><span class="secno">3.12</span> <span class="content">Borrowed Range?</span></a>
     </ol>
    <li><a href="#implementation"><span class="secno">4</span> <span class="content">Implementation</span></a>
    <li>
     <a href="#wording"><span class="secno">5</span> <span class="content">Wording</span></a>
     <ol class="toc">
      <li><a href="#addition-to-ranges"><span class="secno">5.1</span> <span class="content">Addition to <code class="highlight"><c- o>&lt;</c-><c- n>ranges</c-><c- o>></c-></code></span></a>
      <li><a href="#range-adaptor-helpers-rangeadaptorhelpers"><span class="secno">5.2</span> <span class="content">Range adaptor helpers [range.adaptor.helpers]</span></a>
      <li>
       <a href="#cartesian-product-view-rangecartesian"><span class="secno">5.3</span> <span class="content">Cartesian product view [range.cartesian]</span></a>
       <ol class="toc">
        <li><a href="#overview-rangecartesianoverview"><span class="secno">5.3.1</span> <span class="content">Overview [range.cartesian.overview]</span></a>
        <li><a href="#class-template-cartesian_product_view-rangecartesianview"><span class="secno">5.3.2</span> <span class="content">Class template <code class="highlight"><c- n>cartesian_product_view</c-></code> [range.cartesian.view]</span></a>
        <li><a href="#class-template-cartesian_product_viewiterator-rangescartesianiterator"><span class="secno">5.3.3</span> <span class="content">Class template <code class="highlight"><c- n>cartesian_product_view</c-><c- o>::</c-><c- n>iterator</c-></code> [ranges.cartesian.iterator]</span></a>
       </ol>
      <li><a href="#feature-test-macro"><span class="secno">5.4</span> <span class="content">Feature-test macro</span></a>
     </ol>
    <li><a href="#acknowledgements"><span class="secno">6</span> <span class="content">Acknowledgements</span></a>
   </ol>
  </nav>
  <main>
   <h2 class="heading settled" data-level="1" id="changelog"><span class="secno">1. </span><span class="content">Changelog</span><a class="self-link" href="#changelog"></a></h2>
   <h3 class="heading settled" data-level="1.1" id="changes-from-r1"><span class="secno">1.1. </span><span class="content">Changes from r1</span><a class="self-link" href="#changes-from-r1"></a></h3>
   <ul>
    <li data-md>
     <p>Add wording adding <code class="highlight"><c- n>cartesian_product_view</c-></code> into the synopsis of <code class="highlight"><c- o>&lt;</c-><c- n>ranges</c-><c- o>></c-></code></p>
    <li data-md>
     <p>Made the constructor of the view <code class="highlight"><c- k>explicit</c-></code></p>
    <li data-md>
     <p>Added a design section about not making <code class="highlight"><c- n>cartesian_product_view</c-></code> a borrowed range</p>
    <li data-md>
     <p>Added a feature test macro</p>
    <li data-md>
     <p>Use the verbiage about the return type of <code class="highlight"><c- n>size</c-></code> to also define the iterator’s <code class="highlight"><c- n>difference_type</c-></code></p>
    <li data-md>
     <p>Relax the requirements on the first range, allowing it to be an input range</p>
    <li data-md>
     <p>Relax the requirements on the ranges for the view to be a common range - it now only depends on the properties of the first range</p>
    <li data-md>
     <p>Add <code class="highlight"><c- k>operator</c-><c- o>-</c-></code> overloads that allow computing the distance between an iterator and a sentinel</p>
    <li data-md>
     <p>Various wording fixes</p>
   </ul>
   <h3 class="heading settled" data-level="1.2" id="changes-from-r0"><span class="secno">1.2. </span><span class="content">Changes from r0</span><a class="self-link" href="#changes-from-r0"></a></h3>
   <ul>
    <li data-md>
     <p>Specify the return type of <code class="highlight"><c- n>size</c-></code></p>
    <li data-md>
     <p>Add design section on the first range argument</p>
   </ul>
   <h2 class="heading settled" data-level="2" id="motivation"><span class="secno">2. </span><span class="content">Motivation</span><a class="self-link" href="#motivation"></a></h2>
   <p><a href="https://en.wikipedia.org/wiki/Cartesian_product">Cartesian product</a> is a fundamental mathematical construct. There should be a <code class="highlight"><c- n>cartesian_product_view</c-></code> which generates the cartesian product of any number of ranges, e.g.:</p>
   <table>
    <tbody>
     <tr>
      <th>Before
      <th>After
     <tr>
      <td>
<pre class="highlight"><c- n>std</c-><c- o>::</c-><c- n>vector</c-><c- o>&lt;</c-><c- b>int</c-><c- o>></c-> <c- n>a</c-><c- p>,</c-><c- n>b</c-><c- p>,</c-><c- n>c</c-><c- p>;</c->
<c- k>for</c-> <c- p>(</c-><c- k>auto</c-><c- o>&amp;&amp;</c-> <c- nl>ea</c-> <c- p>:</c-> <c- n>a</c-><c- p>)</c-> <c- p>{</c->
    <c- k>for</c-> <c- p>(</c-><c- k>auto</c-><c- o>&amp;&amp;</c-> <c- nl>eb</c-> <c- p>:</c-> <c- n>b</c-><c- p>)</c-> <c- p>{</c->
        <c- k>for</c-> <c- p>(</c-><c- k>auto</c-><c- o>&amp;&amp;</c-> <c- nl>ec</c-> <c- p>:</c-> <c- n>c</c-><c- p>)</c-> <c- p>{</c->
            <c- n>use</c-><c- p>(</c-><c- n>ea</c-><c- p>,</c-><c- n>eb</c-><c- p>,</c-><c- n>ec</c-><c- p>);</c->
        <c- p>}</c->
    <c- p>}</c->
<c- p>}</c->
</pre>
      <td>
<pre class="highlight"><c- n>std</c-><c- o>::</c-><c- n>vector</c-><c- o>&lt;</c-><c- b>int</c-><c- o>></c-> <c- n>a</c-><c- p>,</c-><c- n>b</c-><c- p>,</c-><c- n>c</c-><c- p>;</c->
<c- k>for</c-> <c- p>(</c-><c- k>auto</c-><c- o>&amp;&amp;</c-> <c- p>[</c-><c- n>ea</c-><c- p>,</c-><c- n>eb</c-><c- p>,</c-><c- n>ec</c-><c- p>]</c-> <c- o>:</c-> <c- n>std</c-><c- o>::</c-><c- n>views</c-><c- o>::</c-><c- n>cartesian_product</c-><c- p>(</c-><c- n>a</c-><c- p>,</c-><c- n>b</c-><c- p>,</c-><c- n>c</c-><c- p>))</c-> <c- p>{</c->
    <c- n>use</c-><c- p>(</c-><c- n>ea</c-><c- p>,</c-><c- n>eb</c-><c- p>,</c-><c- n>ec</c-><c- p>);</c->
<c- p>}</c->
</pre>
   </table>
   <p>This is especially useful for composing with other views, or dealing with parameter packs of ranges:</p>
   <table>
    <tbody>
     <tr>
      <th>Before
      <th>After
     <tr>
      <td>
<pre class="highlight"><c- k>template</c-> <c- o>&lt;</c-><c- n>std</c-><c- o>::</c-><c- b>size_t</c-> <c- n>N</c-> <c- o>=</c-> <c- mi>0</c-><c- p>,</c-> <c- k>class</c-> <c- nc>F</c-><c- p>,</c->
          <c- k>class</c-> <c- nc>Res</c-><c- p>,</c-> <c- k>class</c-> <c- nc>Tuple</c-><c- p>,</c-> <c- n>class</c-><c- p>...</c-> <c- n>Args</c-><c- o>></c->
<c- k>auto</c-> <c- n>find_tuples_satisfying_impl</c-><c- p>(</c->
    <c- n>F</c-> <c- n>f</c-><c- p>,</c-> <c- n>Res</c-><c- o>&amp;</c-> <c- n>res</c-><c- p>,</c-> <c- n>Tuple</c-> <c- k>const</c-><c- o>&amp;</c-> <c- n>ranges</c-><c- p>,</c-> <c- n>Args</c-> <c- k>const</c-><c- o>&amp;</c-><c- p>...</c-> <c- n>args</c-><c- p>)</c->
<c- k>requires</c-><c- p>(</c-><c- n>N</c-> <c- o>==</c-> <c- n>std</c-><c- o>::</c-><c- n>tuple_size_v</c-><c- o>&lt;</c-><c- n>std</c-><c- o>::</c-><c- n>remove_cvref_t</c-><c- o>&lt;</c-><c- n>Tuple</c-><c- o>>></c-><c- p>)</c-> <c- p>{</c->
  <c- k>if</c-> <c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>invoke</c-><c- p>(</c-><c- n>f</c-><c- p>,</c-> <c- n>args</c-><c- p>...))</c-> <c- p>{</c->
    <c- n>res</c-><c- p>.</c-><c- n>push_back</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>make_tuple</c-><c- p>(</c-><c- n>args</c-><c- p>...));</c->
  <c- p>}</c->
<c- p>}</c->

<c- k>template</c-> <c- o>&lt;</c-><c- n>std</c-><c- o>::</c-><c- b>size_t</c-> <c- n>N</c-> <c- o>=</c-> <c- mi>0</c-><c- p>,</c-> <c- k>class</c-> <c- nc>F</c-><c- p>,</c->
          <c- k>class</c-> <c- nc>Res</c-><c- p>,</c-> <c- k>class</c-> <c- nc>Tuple</c-><c- p>,</c-> <c- n>class</c-><c- p>...</c-> <c- n>Args</c-><c- o>></c->
<c- k>auto</c-> <c- n>find_tuples_satisfying_impl</c-><c- p>(</c->
    <c- n>F</c-> <c- n>f</c-><c- p>,</c-> <c- n>Res</c-><c- o>&amp;</c-> <c- n>res</c-><c- p>,</c-> <c- n>Tuple</c-> <c- k>const</c-><c- o>&amp;</c-> <c- n>ranges</c-><c- p>,</c-> <c- n>Args</c-> <c- k>const</c-><c- o>&amp;</c-><c- p>...</c-> <c- n>args</c-><c- p>)</c-> <c- p>{</c->
  <c- k>for</c-> <c- p>(</c-><c- k>auto</c-><c- o>&amp;&amp;</c-> <c- nl>e</c-> <c- p>:</c-> <c- n>std</c-><c- o>::</c-><c- n>get</c-><c- o>&lt;</c-><c- n>N</c-><c- o>></c-><c- p>(</c-><c- n>ranges</c-><c- p>))</c-> <c- p>{</c->
    <c- n>find_tuples_satisfying_impl</c-><c- o>&lt;</c-><c- n>N</c-><c- o>+</c-><c- mi>1</c-><c- o>></c-><c- p>(</c-><c- n>f</c-><c- p>,</c-> <c- n>res</c-><c- p>,</c-> <c- n>ranges</c-><c- p>,</c-> <c- n>args</c-><c- p>...,</c-> <c- n>e</c-><c- p>);</c->
  <c- p>}</c->
<c- p>}</c->

<c- k>template</c-> <c- o>&lt;</c-><c- k>class</c-> <c- nc>F</c-><c- p>,</c-> <c- n>std</c-><c- o>::</c-><c- n>ranges</c-><c- o>::</c-><c- n>forward_range</c-><c- p>...</c-> <c- n>Vs</c-><c- o>></c->
<c- k>requires</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>regular_invocable</c-><c- o>&lt;</c->
          <c- n>F</c-><c- p>,</c-> <c- n>std</c-><c- o>::</c-><c- n>ranges</c-><c- o>::</c-><c- n>range_reference_t</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>)</c->
<c- k>auto</c-> <c- n>find_tuples_satisfying</c-><c- p>(</c-><c- n>F</c-> <c- n>f</c-><c- p>,</c-> <c- n>Vs</c-><c- o>&amp;&amp;</c-><c- p>...</c-> <c- n>vs</c-><c- p>)</c-> <c- p>{</c->
  <c- n>std</c-><c- o>::</c-><c- n>vector</c-><c- o>&lt;</c-><c- n>std</c-><c- o>::</c-><c- n>tuple</c-><c- o>&lt;</c-><c- n>std</c-><c- o>::</c-><c- n>ranges</c-><c- o>::</c-><c- n>range_value_t</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>>></c-> <c- n>res</c-><c- p>;</c->
  <c- n>find_tuples_satisfying_impl</c-><c- p>(</c->
        <c- n>f</c-><c- p>,</c-> <c- n>res</c-><c- p>,</c-> <c- n>std</c-><c- o>::</c-><c- n>tuple</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>forward</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>&amp;&amp;></c-><c- p>(</c-><c- n>vs</c-><c- p>)...));</c->
  <c- k>return</c-> <c- n>res</c-><c- p>;</c->
<c- p>}</c->
</pre>
      <td>
<pre class="highlight"><c- k>template</c-> <c- o>&lt;</c-><c- k>class</c-> <c- nc>F</c-><c- p>,</c-> <c- n>std</c-><c- o>::</c-><c- n>ranges</c-><c- o>::</c-><c- n>forward_range</c-><c- p>...</c-> <c- n>Vs</c-><c- o>></c->
<c- k>requires</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>regular_invocable</c-><c- o>&lt;</c-><c- n>F</c-><c- p>,</c->
          <c- n>std</c-><c- o>::</c-><c- n>ranges</c-><c- o>::</c-><c- n>range_reference_t</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>)</c->
<c- k>auto</c-> <c- n>find_tuples_satisfying</c-><c- p>(</c-><c- n>F</c-> <c- n>f</c-><c- p>,</c-> <c- n>Vs</c-><c- o>&amp;&amp;</c-><c- p>...</c-> <c- n>vs</c-><c- p>)</c-> <c- p>{</c->
  <c- k>return</c-> <c- n>std</c-><c- o>::</c-><c- n>views</c-><c- o>::</c-><c- n>cartesian_product</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>forward</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>(</c-><c- n>vs</c-><c- p>)...)</c->
    <c- o>|</c-> <c- n>std</c-><c- o>::</c-><c- n>views</c-><c- o>::</c-><c- n>filter</c-><c- p>([</c-><c- n>f</c-><c- p>](</c-><c- k>auto</c-><c- o>&amp;&amp;</c-> <c- n>tuple</c-><c- p>)</c-> <c- p>{</c-> <c- k>return</c-> <c- n>std</c-><c- o>::</c-><c- n>apply</c-><c- p>(</c-><c- n>f</c-><c- p>,</c-> <c- n>tuple</c-><c- p>);</c-> <c- p>});)</c->
    <c- o>|</c-> <c- n>std</c-><c- o>::</c-><c- n>ranges</c-><c- o>::</c-><c- n>to</c-><c- o>&lt;</c-><c- n>std</c-><c- o>::</c-><c- n>vector</c-><c- o>></c-><c- p>();</c-> <c- c1>//given P1206</c->
<c- p>}</c->
</pre>
   </table>
   <h2 class="heading settled" data-level="3" id="design"><span class="secno">3. </span><span class="content">Design</span><a class="self-link" href="#design"></a></h2>
   <h3 class="heading settled" data-level="3.1" id="minimum-range-requirements"><span class="secno">3.1. </span><span class="content">Minimum Range Requirements</span><a class="self-link" href="#minimum-range-requirements"></a></h3>
    This paper requires all ranges, except the first one, passed to <code class="highlight"><c- n>cartesian_product_view</c-></code> to be forward ranges. See <a href="#initialrange">Initial Range Argument Special-Casing</a> for discussion on the first argument being an input range. 
   <h3 class="heading settled" data-level="3.2" id="tuple-or-pair"><span class="secno">3.2. </span><span class="content">Tuple or pair</span><a class="self-link" href="#tuple-or-pair"></a></h3>
    A potential design would be to use <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>tuple</c-></code> as the <code class="highlight"><c- n>value_type</c-></code> and <code class="highlight"><c- n>reference_type</c-></code> of <code class="highlight"><c- n>cartesian_product_view</c-></code>. This paper uses <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>pair</c-></code> if two ranges are passed and <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>tuple</c-></code> otherwise. See <a href="https://wg21.link/p2321">p2321</a> for motivation. 
   <h3 class="heading settled" data-level="3.3" id="reference_type"><span class="secno">3.3. </span><span class="content"><code class="highlight"><c- n>reference_type</c-></code></span><a class="self-link" href="#reference_type"></a></h3>
    This paper uses <code class="highlight"><c- n>tuple</c-><c- o>-</c-><c- n>or</c-><c- o>-</c-><c- n>pair</c-><c- o>&lt;</c-><c- n>ranges</c-><c- o>::</c-><c- n>reference_t</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-></code> as the reference type. See <a href="http://wg21.link/p2214">p2214</a> for discussion of value types (particularly <code class="highlight"><c- n>pair</c-></code> and <code class="highlight"><c- n>tuple</c-></code>) as the <code class="highlight"><c- n>reference_type</c-></code> for ranges, and <a href="https://wg21.link/p2321">p2321</a> for wording of improvements for key use-cases. 
   <h3 class="heading settled" data-level="3.4" id="empty-cartesian-product-view"><span class="secno">3.4. </span><span class="content">Empty cartesian product view</span><a class="self-link" href="#empty-cartesian-product-view"></a></h3>
    Trying to take the cartesian product view of 0 views will produce an <code class="highlight"><c- n>empty_view</c-><c- o>&lt;</c-><c- n>tuple</c-><c- o>&lt;>></c-></code>, in parity with Range-v3 and <a href="https://wg21.link/p2321">p2321</a>. 
   <h3 class="heading settled" data-level="3.5" id="common-range"><span class="secno">3.5. </span><span class="content">Common Range</span><a class="self-link" href="#common-range"></a></h3>
    <code class="highlight"><c- n>cartesian_product_view</c-></code> can be a common range if the first range either is common, or is sized and random access. This paper reflects this. 
   <h3 class="heading settled" data-level="3.6" id="bidirectional-range"><span class="secno">3.6. </span><span class="content">Bidirectional Range</span><a class="self-link" href="#bidirectional-range"></a></h3>
    <code class="highlight"><c- n>cartesian_product_view</c-></code> can be a bidirectional range if the underlying ranges, except for the first one, are bidirectional and common, or if they are random access and sized. Non-common bidirectional ranges are not supported because decrementing when one of the iterators is at the beginning of its range would require advancing the iterator to end, which may be linear in complexity. 
   <p>We don’t consider non-common, random access, sized ranges as worth supporting, so this paper requires bidirectional and common.</p>
   <h3 class="heading settled" data-level="3.7" id="random-access-range"><span class="secno">3.7. </span><span class="content">Random Access Range</span><a class="self-link" href="#random-access-range"></a></h3>
    <code class="highlight"><c- n>cartesian_product_view</c-></code> can be a random access range if all the underlying ranges are random access and sized, with the second requirement not appling to the first range. Sized ranges are required because when the view is incremented, the new states of the iterators are calculated modulo the size of their views. 
   <p>We can’t think of too many use-cases for this and it adds a fair bit of implementation burden, but this paper supports the necessary operations.</p>
   <h3 class="heading settled" data-level="3.8" id="initialrange"><span class="secno">3.8. </span><span class="content">Initial Range Argument Special-Casing</span><a class="self-link" href="#initialrange"></a></h3>
    The first range passed to <code class="highlight"><c- n>cartesian_product_view</c-></code> can be treated specially, since it is only passed through a single time. Therefore, the specification relaxes several constraints on the first range passed: 
   <ul>
    <li data-md>
     <p>It could be an input range instead of forward range</p>
    <li data-md>
     <p>It wouldn’t need to be a sized range in order for the <code class="highlight"><c- n>cartesian_product_view</c-></code> to be random-access or common</p>
    <li data-md>
     <p>It wouldn’t need to be common in order for the <code class="highlight"><c- n>cartesian_product_view</c-></code> to be bidirectional</p>
   </ul>
   <p>Previous revisions of this paper didn’t propose this feature, however the Ranges SG has requested that it be added to the paper.</p>
   <h3 class="heading settled" data-level="3.9" id="sized-range"><span class="secno">3.9. </span><span class="content">Sized Range</span><a class="self-link" href="#sized-range"></a></h3>
    <code class="highlight"><c- n>cartesian_product_view</c-></code> can be a sized range if all the underlying ranges are, in which case the size is the product of all underlying sizes. This is reflected in the paper. 
   <h3 class="heading settled" data-level="3.10" id="naming"><span class="secno">3.10. </span><span class="content">Naming</span><a class="self-link" href="#naming"></a></h3>
    An alternative name is <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>ranges</c-><c- o>::</c-><c- n>product_view</c-></code>. This paper uses <code class="highlight"><c- n>cartesian_product_view</c-></code> as we believe it is more explicit in what its semantics are. 
   <h3 class="heading settled" data-level="3.11" id="pipe-support"><span class="secno">3.11. </span><span class="content">Pipe Support</span><a class="self-link" href="#pipe-support"></a></h3>
    It may be possible to support syntax such as <code class="highlight"><c- n>vec1</c-> <c- o>|</c-> <c- n>views</c-><c- o>::</c-><c- n>cartesian_product</c-><c- p>(</c-><c- n>vec2</c-><c- p>)</c-></code> by either fixing the number of arguments allowed to the view, or adding a pipe operator to <code class="highlight"><c- n>cartesian_product_view</c-></code> itself. 
   <p>However, it’s problematic for the same reason as <code class="highlight"><c- n>views</c-><c- o>::</c-><c- n>zip</c-></code>, in that one cannot distinguish between the usages in <code class="highlight"><c- n>a</c-> <c- o>|</c-> <c- n>views</c-><c- o>::</c-><c- n>cartesian_product</c-><c- p>(</c-><c- n>b</c-><c- p>,</c-> <c- n>c</c-><c- p>)</c-></code> and <code class="highlight"><c- n>views</c-><c- o>::</c-><c- n>cartesian_product</c-><c- p>(</c-><c- n>b</c-><c- p>,</c-><c- n>c</c-><c- p>)</c-></code> on its own. As such, this paper does not support this syntax.</p>
   <h3 class="heading settled" data-level="3.12" id="borrowed-range"><span class="secno">3.12. </span><span class="content">Borrowed Range?</span><a class="self-link" href="#borrowed-range"></a></h3>
    It is possible to implement <code class="highlight"><c- n>cartesian_product_view</c-></code> in such a way that it is a borrowed range if all the underlying ranges are borrowed. However, this requires that every iterator of the view stores two iterators per every range used for the cartesian product - one for the current position within that range, and another for the begin iterator, to allow wrapping around back to the first element when the end of that range is reached. (For random access underlying ranges, it is conceivable to store an iterator and an offset, but this is not applicable in general.) If <code class="highlight"><c- n>cartesian_product_view</c-></code> is not a borrowed view, the iterators only require storing one iterator per every range, and a pointer to the view itself. 
   <p>Due to this, this paper does not make <code class="highlight"><c- n>cartesian_product_view</c-></code> a borrowed range.</p>
   <h2 class="heading settled" data-level="4" id="implementation"><span class="secno">4. </span><span class="content">Implementation</span><a class="self-link" href="#implementation"></a></h2>
    There are implementations of a cartesian product view in <a href="https://github.com/ericniebler/range-v3/blob/master/include/range/v3/view/cartesian_product.hpp">Range-v3</a>, <a href="https://github.com/cor3ntin/rangesnext/blob/master/include/cor3ntin/rangesnext/product.hpp">cor3ntin::rangesnext</a>, and <a href="https://github.com/tartanllama/ranges">tl::ranges</a>, among others. 
   <h2 class="heading settled" data-level="5" id="wording"><span class="secno">5. </span><span class="content">Wording</span><a class="self-link" href="#wording"></a></h2>
   <h3 class="heading settled" data-level="5.1" id="addition-to-ranges"><span class="secno">5.1. </span><span class="content">Addition to <code class="highlight"><c- o>&lt;</c-><c- n>ranges</c-><c- o>></c-></code></span><a class="self-link" href="#addition-to-ranges"></a></h3>
   <p>Add the following to 24.2 [ranges.syn], Header <code class="highlight"><c- o>&lt;</c-><c- n>ranges</c-><c- o>></c-></code> synopsis:</p>
<pre class="highlight"><c- c1>// ...</c->
<c- k>namespace</c-> <c- nl>std</c-><c- p>:;</c-><c- n>ranges</c-> <c- p>{</c->
    <c- c1>// ...</c->

    <c- c1>// [range.cartesian], cartesian product view</c->
    <c- k>template</c-><c- o>&lt;</c-><c- n>input_range</c-> <c- n>First</c-><c- p>,</c-> <c- n>forward_range</c-><c- p>...</c-> <c- n>Vs</c-><c- o>></c->
        <c- k>requires</c-> <c- p>(</c-><c- n>view</c-><c- o>&lt;</c-><c- n>First</c-><c- o>></c-> <c- o>&amp;&amp;</c-> <c- p>(</c-><c- n>view</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-> <c- o>&amp;&amp;</c-> <c- p>...))</c->
    <c- k>class</c-> <c- nc>cartesian_product_view</c-><c- p>;</c->

    <c- k>namespace</c-> <c- n>views</c-> <c- p>{</c-> <c- kr>inline</c-> <c- k>constexpr</c-> <c- n>unspecified</c-> <c- n>cartesian_product</c-> <c- o>=</c-> <c- n>unspecified</c-><c- p>;</c-> <c- p>}</c->
<c- p>}</c->
</pre>
   <h3 class="heading settled" data-level="5.2" id="range-adaptor-helpers-rangeadaptorhelpers"><span class="secno">5.2. </span><span class="content">Range adaptor helpers [range.adaptor.helpers]</span><a class="self-link" href="#range-adaptor-helpers-rangeadaptorhelpers"></a></h3>
   <p>New section after Non-propagating cache [range.nonprop.cache]. Move the definitions of <code class="highlight"><c- n>tuple</c-><c- o>-</c-><c- n>or</c-><c- o>-</c-><c- n>pair</c-></code>, <code class="highlight"><c- n>tuple</c-><c- o>-</c-><c- n>transform</c-></code>, and <code class="highlight"><c- n>tuple</c-><c- o>-</c-><c- k>for</c-><c- o>-</c-><c- n>each</c-></code> from Class template <code class="highlight"><c- n>zip_view</c-></code> [range.zip.view] to this section:</p>
<pre class="highlight"><c- k>namespace</c-> <c- n>std</c-><c- o>::</c-><c- n>ranges</c-> <c- p>{</c->
    <c- k>template</c-> <c- o>&lt;</c-><c- n>class</c-><c- p>...</c-> <c- n>Ts</c-><c- o>></c->
    <c- k>using</c-> <c- n>tuple</c-><c- o>-</c-><c- n>or</c-><c- o>-</c-><c- n>pair</c-> <c- o>=</c-> <c- n>see</c-><c- o>-</c-><c- n>below</c-><c- p>;</c->                     <c- c1>// exposition only</c->

    <c- k>template</c-><c- o>&lt;</c-><c- k>class</c-> <c- nc>F</c-><c- p>,</c-> <c- k>class</c-> <c- nc>Tuple</c-><c- o>></c->
    <c- k>constexpr</c-> <c- k>auto</c-> <c- n>tuple</c-><c- o>-</c-><c- n>transform</c-><c- p>(</c-><c- n>F</c-><c- o>&amp;&amp;</c-> <c- n>f</c-><c- p>,</c-> <c- n>Tuple</c-><c- o>&amp;&amp;</c-> <c- n>tuple</c-><c- p>)</c-> <c- p>{</c-> <c- c1>// exposition only</c->
        <c- k>return</c-> <c- n>apply</c-><c- p>([</c-><c- o>&amp;</c-><c- p>]</c-><c- o>&lt;</c-><c- n>class</c-><c- p>...</c-> <c- n>Ts</c-><c- o>></c-><c- p>(</c-><c- n>Ts</c-><c- o>&amp;&amp;</c-><c- p>...</c-> <c- n>elements</c-><c- p>)</c-> <c- p>{</c->
            <c- k>return</c-> <c- n>tuple</c-><c- o>-</c-><c- n>or</c-><c- o>-</c-><c- n>pair</c-><c- o>&lt;</c-><c- n>invoke_result_t</c-><c- o>&lt;</c-><c- n>F</c-><c- o>&amp;</c-><c- p>,</c-> <c- n>Ts</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>(</c->
                <c- n>invoke</c-><c- p>(</c-><c- n>f</c-><c- p>,</c-> <c- n>std</c-><c- o>::</c-><c- n>forward</c-><c- o>&lt;</c-><c- n>Ts</c-><c- o>></c-><c- p>(</c-><c- n>elements</c-><c- p>))...</c->
            <c- p>);</c->
        <c- p>},</c-> <c- n>std</c-><c- o>::</c-><c- n>forward</c-><c- o>&lt;</c-><c- n>Tuple</c-><c- o>></c-><c- p>(</c-><c- n>tuple</c-><c- p>));</c->
    <c- p>}</c->

    <c- k>template</c-><c- o>&lt;</c-><c- k>class</c-> <c- nc>F</c-><c- p>,</c-> <c- k>class</c-> <c- nc>Tuple</c-><c- o>></c->
    <c- k>constexpr</c-> <c- b>void</c-> <c- n>tuple</c-><c- o>-</c-><c- k>for</c-><c- o>-</c-><c- n>each</c-><c- p>(</c-><c- n>F</c-><c- o>&amp;&amp;</c-> <c- n>f</c-><c- p>,</c-> <c- n>Tuple</c-><c- o>&amp;&amp;</c-> <c- n>tuple</c-><c- p>)</c-> <c- p>{</c-> <c- c1>// exposition only</c->
        <c- n>apply</c-><c- p>([</c-><c- o>&amp;</c-><c- p>]</c-><c- o>&lt;</c-><c- n>class</c-><c- p>...</c-> <c- n>Ts</c-><c- o>></c-><c- p>(</c-><c- n>Ts</c-><c- o>&amp;&amp;</c-><c- p>...</c-> <c- n>elements</c-><c- p>)</c-> <c- p>{</c->
            <c- p>(</c-><c- n>invoke</c-><c- p>(</c-><c- n>f</c-><c- p>,</c-> <c- n>std</c-><c- o>::</c-><c- n>forward</c-><c- o>&lt;</c-><c- n>Ts</c-><c- o>></c-><c- p>(</c-><c- n>elements</c-><c- p>)),</c-> <c- p>...);</c->
        <c- p>},</c-> <c- n>std</c-><c- o>::</c-><c- n>forward</c-><c- o>&lt;</c-><c- n>Tuple</c-><c- o>></c-><c- p>(</c-><c- n>tuple</c-><c- p>));</c->
    <c- p>}</c->
<c- p>}</c->
</pre>
   <p>Given some pack of types Ts, the alias template tuple-or-pair is defined as follows:</p>
   <ol>
    <li data-md>
     <p>If <code class="highlight"><c- k>sizeof</c-><c- p>...(</c-><c- n>Ts</c-><c- p>)</c-></code> is 2, <code class="highlight"><c- n>tuple</c-><c- o>-</c-><c- n>or</c-><c- o>-</c-><c- n>pair</c-><c- o>&lt;</c-><c- n>Ts</c-><c- p>...</c-><c- o>></c-></code> denotes <code class="highlight"><c- n>pair</c-><c- o>&lt;</c-><c- n>Ts</c-><c- p>...</c-><c- o>></c-></code>.</p>
    <li data-md>
     <p>Otherwise, <code class="highlight"><c- n>tuple</c-><c- o>-</c-><c- n>or</c-><c- o>-</c-><c- n>pair</c-><c- o>&lt;</c-><c- n>Ts</c-><c- p>...</c-><c- o>></c-></code> denotes <code class="highlight"><c- n>tuple</c-><c- o>&lt;</c-><c- n>Ts</c-><c- p>...</c-><c- o>></c-></code>.</p>
   </ol>
   <h3 class="heading settled" data-level="5.3" id="cartesian-product-view-rangecartesian"><span class="secno">5.3. </span><span class="content">Cartesian product view [range.cartesian]</span><a class="self-link" href="#cartesian-product-view-rangecartesian"></a></h3>
   <h4 class="heading settled" data-level="5.3.1" id="overview-rangecartesianoverview"><span class="secno">5.3.1. </span><span class="content">Overview [range.cartesian.overview]</span><a class="self-link" href="#overview-rangecartesianoverview"></a></h4>
   <p><code class="highlight"><c- n>cartesian_product_view</c-></code> presents a <code class="highlight"><c- n>view</c-></code> with a value type that represents the cartesian product of the adapted ranges.</p>
   <p>The name <code class="highlight"><c- n>views</c-><c- o>::</c-><c- n>cartesian_product</c-></code> denotes a customization point object. Given a pack of subexpressions <code class="highlight"><c- n>Es</c-><c- p>...</c-></code>, the expression <code class="highlight"><c- n>views</c-><c- o>::</c-><c- n>cartesian_product</c-><c- p>(</c-><c- n>Es</c-><c- p>...)</c-></code> is expression-equivalent to</p>
   <ul>
    <li data-md>
     <p><code class="highlight"><c- o>*</c-><c- n>decay</c-><c- o>-</c-><c- n>copy</c-><c- o>*</c-><c- p>(</c-><c- n>views</c-><c- o>::</c-><c- n>empty</c-><c- o>&lt;</c-><c- n>tuple</c-><c- o>&lt;>></c-><c- p>)</c-></code> if <code class="highlight"><c- n>Es</c-></code> is an empty pack,</p>
    <li data-md>
     <p>otherwise, <code class="highlight"><c- n>cartesian_product_view</c-><c- o>&lt;</c-><c- n>views</c-><c- o>::</c-><c- n>all_t</c-><c- o>&lt;</c-><c- k>decltype</c-><c- p>((</c-><c- n>Es</c-><c- p>))</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>(</c-><c- n>Es</c-><c- p>...)</c-></code>.</p>
   </ul>
   <p>[Example:</p>
<pre class="highlight"><c- n>std</c-><c- o>::</c-><c- n>vector</c-><c- o>&lt;</c-><c- b>int</c-><c- o>></c-> <c- n>v</c-> <c- p>{</c-> <c- mi>0</c-><c- p>,</c-> <c- mi>1</c-><c- p>,</c-> <c- mi>2</c-> <c- p>};</c->
<c- k>for</c-> <c- p>(</c-><c- k>auto</c-><c- o>&amp;&amp;</c-> <c- p>[</c-><c- n>a</c-><c- p>,</c-><c- n>b</c-><c- p>,</c-><c- n>c</c-><c- p>]</c-> <c- o>:</c-> <c- n>std</c-><c- o>::</c-><c- n>views</c-><c- o>::</c-><c- n>cartesian_product</c-><c- p>(</c-><c- n>v</c-><c- p>,</c-> <c- n>v</c-><c- p>,</c-> <c- n>v</c-><c- p>))</c-> <c- p>{</c->
  <c- n>std</c-><c- o>::</c-><c- n>cout</c-> <c- o>&lt;&lt;</c-> <c- n>a</c-> <c- o>&lt;&lt;</c-> <c- sc>' '</c-> <c- o>&lt;&lt;</c-> <c- n>b</c-> <c- o>&lt;&lt;</c-> <c- sc>' '</c-> <c- o>&lt;&lt;</c-> <c- n>c</c-> <c- o>&lt;&lt;</c-> <c- sc>'\n'</c-><c- p>;</c->
  <c- c1>//0 0 0</c->
  <c- c1>//0 0 1</c->
  <c- c1>//0 0 2</c->
  <c- c1>//0 1 0</c->
  <c- c1>//0 1 1</c->
  <c- c1>//...</c->
<c- p>}</c->
</pre>
   -- end example ] 
   <h4 class="heading settled" data-level="5.3.2" id="class-template-cartesian_product_view-rangecartesianview"><span class="secno">5.3.2. </span><span class="content">Class template <code class="highlight"><c- n>cartesian_product_view</c-></code> [range.cartesian.view]</span><a class="self-link" href="#class-template-cartesian_product_view-rangecartesianview"></a></h4>
<pre class="highlight"><c- k>namespace</c-> <c- n>std</c-><c- o>::</c-><c- n>ranges</c-> <c- p>{</c->
    <c- k>template</c-> <c- o>&lt;</c-><c- k>class</c-> <c- nc>First</c-><c- p>,</c-> <c- n>class</c-><c- p>...</c-> <c- n>Vs</c-><c- o>></c->
    <c- k>concept</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>random</c-><c- o>-</c-><c- n>access</c-> <c- o>=</c-> <c- c1>// exposition only</c->
      <c- p>(</c-><c- n>random_access_range</c-><c- o>&lt;</c-><c- n>First</c-><c- o>></c-> <c- o>&amp;&amp;</c-> <c- p>...</c-> <c- o>&amp;&amp;</c->
        <c- p>(</c-><c- n>random_access_range</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-> <c- o>&amp;&amp;</c-> <c- n>sized_range</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>));</c->

    <c- k>template</c-> <c- o>&lt;</c-><c- k>class</c-> <c- nc>R</c-><c- o>></c->
    <c- k>concept</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>common</c-><c- o>-</c-><c- n>arg</c-> <c- o>=</c-> <c- c1>// exposition only</c->
      <c- n>common_range</c-><c- o>&lt;</c-><c- n>R</c-><c- o>></c-> <c- o>||</c-> <c- p>(</c-><c- n>sized_range</c-><c- o>&lt;</c-><c- n>R</c-><c- o>></c-> <c- o>&amp;&amp;</c-> <c- n>random_access_range</c-><c- o>&lt;</c-><c- n>R</c-><c- o>></c-><c- p>);</c->

    <c- k>template</c-> <c- o>&lt;</c-><c- k>class</c-> <c- nc>First</c-><c- p>,</c-> <c- n>class</c-><c- p>...</c-> <c- n>Vs</c-><c- o>></c->
    <c- k>concept</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>bidirectional</c-> <c- o>=</c-> <c- c1>// exposition only</c->
      <c- p>(</c-><c- n>bidirectional_range</c-><c- o>&lt;</c-><c- n>First</c-><c- o>></c-> <c- o>&amp;&amp;</c-> <c- p>...</c-> <c- o>&amp;&amp;</c->
        <c- p>(</c-><c- n>bidirectional_range</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-> <c- o>&amp;&amp;</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>common</c-><c- o>-</c-><c- n>arg</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>));</c->

    <c- k>template</c-> <c- o>&lt;</c-><c- k>class</c-> <c- nc>First</c-><c- p>,</c-> <c- n>class</c-><c- p>...</c-> <c- n>Vs</c-><c- o>></c->
    <c- k>concept</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>common</c-> <c- o>=</c-> <c- c1>// exposition only</c->
      <c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>common</c-><c- o>-</c-><c- n>arg</c-><c- o>&lt;</c-><c- n>First</c-><c- o>></c-><c- p>;</c->

    <c- k>template</c-> <c- o>&lt;</c-><c- n>class</c-><c- p>...</c-> <c- n>Vs</c-><c- o>></c->
    <c- k>concept</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>sized</c-> <c- o>=</c-> <c- c1>// exposition only</c->
      <c- p>(</c-><c- n>sized_range</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-> <c- o>&amp;&amp;</c-> <c- p>...);</c->

    <c- k>template</c-><c- o>&lt;</c-><c- k>typename</c-> <c- n>First</c-><c- p>,</c-> <c- k>typename</c-><c- p>...</c-> <c- n>Vs</c-><c- o>></c->
      <c- k>concept</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>sentinel</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>sized</c-> <c- o>=</c-> <c- c1>// exposition only</c->
        <c- n>sized_sentinel_for</c-><c- o>&lt;</c-><c- n>sentinel_t</c-><c- o>&lt;</c-><c- n>First</c-><c- o>></c-><c- p>,</c-> <c- n>iterator_t</c-><c- o>&lt;</c-><c- n>First</c-><c- o>>></c-> <c- o>&amp;&amp;</c-> <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>sized_range</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>;</c->

    <c- k>template</c-> <c- o>&lt;</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>common</c-><c- o>-</c-><c- n>arg</c-> <c- n>R</c-><c- o>></c->
    <c- k>auto</c-> <c- n>cartiesian</c-><c- o>-</c-><c- n>common</c-><c- o>-</c-><c- n>arg</c-><c- o>-</c-><c- n>end</c-><c- p>(</c-><c- n>R</c-> <c- o>&amp;</c-> <c- n>r</c-><c- p>)</c-> <c- p>{</c->
      <c- k>if</c-> <c- k>constexpr</c-> <c- p>(</c-><c- n>common_range</c-><c- o>&lt;</c-><c- n>R</c-><c- o>></c-><c- p>)</c-> <c- p>{</c->
        <c- k>return</c-> <c- n>std</c-><c- o>::</c-><c- n>ranges</c-><c- o>::</c-><c- n>end</c-><c- p>(</c-><c- n>r</c-><c- p>);</c->
      <c- p>}</c->
      <c- k>else</c-> <c- p>{</c->
        <c- k>return</c-> <c- n>std</c-><c- o>::</c-><c- n>ranges</c-><c- o>::</c-><c- n>begin</c-><c- p>(</c-><c- n>r</c-><c- p>)</c-> <c- o>+</c-> <c- n>std</c-><c- o>::</c-><c- n>ranges</c-><c- o>::</c-><c- n>size</c-><c- p>(</c-><c- n>r</c-><c- p>);</c->
      <c- p>}</c->
    <c- p>}</c->

    <c- k>template</c-> <c- o>&lt;</c-><c- n>input_range</c-> <c- n>First</c-><c- p>,</c-> <c- n>forward_range</c-><c- p>...</c-> <c- n>Vs</c-><c- o>></c->
      <c- k>requires</c-> <c- p>(</c-><c- n>view</c-><c- o>&lt;</c-><c- n>First</c-><c- o>></c-> <c- o>&amp;&amp;</c-> <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>view</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>)</c->
    <c- k>class</c-> <c- nc>cartesian_product_view</c->
    <c- o>:</c-> <c- k>public</c-> <c- n>view_interface</c-><c- o>&lt;</c-><c- n>cartesian_product_view</c-><c- o>&lt;</c-><c- n>First</c-><c- p>,</c-> <c- n>Vs</c-><c- p>...</c-><c- o>>></c-> <c- p>{</c->
    <c- k>private</c-><c- o>:</c->
        <c- n>std</c-><c- o>::</c-><c- n>tuple</c-><c- o>&lt;</c-><c- n>First</c-><c- p>,</c-> <c- n>Vs</c-><c- p>...</c-><c- o>></c-> <c- n>bases_</c-><c- p>;</c-> <c- c1>// exposition only</c->

        <c- k>template</c-><c- o>&lt;</c-><c- b>bool</c-> <c- n>Const</c-><c- o>></c->
        <c- k>struct</c-> <c- n>iterator</c-><c- p>;</c-> <c- c1>// exposition only</c->
    <c- k>public</c-><c- o>:</c->
        <c- k>constexpr</c-> <c- n>cartesian_product_view</c-><c- p>()</c-> <c- o>=</c-> <c- k>default</c-><c- p>;</c->
        <c- k>constexpr</c-> <c- k>explicit</c-> <c- nf>cartesian_product_view</c-><c- p>(</c-><c- n>First</c-> <c- n>first_base</c-><c- p>,</c-> <c- n>Vs</c-><c- p>...</c-> <c- n>bases</c-><c- p>);</c->

        <c- k>constexpr</c-> <c- n>iterator</c-><c- o>&lt;</c->false<c- o>></c-> <c- n>begin</c-><c- p>()</c->
          <c- k>requires</c-> <c- p>(</c-><c- o>!</c-><c- n>simple_view</c-><c- o>&lt;</c-><c- n>First</c-><c- o>></c-> <c- o>||</c-> <c- p>...</c-> <c- o>||</c-> <c- o>!</c-><c- n>simple_view</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>);</c->
        <c- k>constexpr</c-> <c- n>iterator</c-><c- o>&lt;</c->true<c- o>></c-> <c- n>begin</c-><c- p>()</c-> <c- k>const</c->
          <c- k>requires</c-> <c- p>(</c-><c- n>range</c-><c- o>&lt;</c-><c- k>const</c-> <c- n>First</c-><c- o>></c-> <c- o>&amp;&amp;</c-> <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>range</c-><c- o>&lt;</c-><c- k>const</c-> <c- n>Vs</c-><c- o>></c-><c- p>);</c->

        <c- k>constexpr</c-> <c- n>iterator</c-><c- o>&lt;</c->false<c- o>></c-> <c- n>end</c-><c- p>()</c->
          <c- k>requires</c-> <c- p>((</c-><c- o>!</c-><c- n>simple_view</c-><c- o>&lt;</c-><c- n>First</c-><c- o>></c-> <c- o>||</c-> <c- p>...</c-> <c- o>||</c-> <c- o>!</c-><c- n>simple_view</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>)</c-> <c- o>&amp;&amp;</c->
            <c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>common</c-><c- o>&lt;</c-><c- n>First</c-><c- p>,</c-> <c- n>Vs</c-><c- p>...</c-><c- o>></c-><c- p>);</c->
        <c- k>constexpr</c-> <c- n>iterator</c-><c- o>&lt;</c->true<c- o>></c-> <c- n>end</c-><c- p>()</c-> <c- k>const</c->
          <c- k>requires</c-><c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>common</c-><c- o>&lt;</c-><c- k>const</c-> <c- n>First</c-><c- p>,</c-> <c- k>const</c-> <c- n>Vs</c-><c- p>...</c-><c- o>></c-><c- p>);</c->
        <c- k>constexpr</c-> <c- n>default_sentinel_t</c-> <c- nf>end</c-><c- p>()</c-> <c- k>const</c->
          <c- k>requires</c-> <c- p>(</c-><c- o>!</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>common</c-><c- o>&lt;</c-><c- k>const</c-> <c- n>First</c-><c- p>,</c-> <c- k>const</c-> <c- n>Vs</c-><c- p>...</c-><c- o>></c-><c- p>);</c->

        <c- k>constexpr</c-> <c- o>*</c-><c- n>see</c-> <c- n>below</c-><c- o>*</c-> <c- nf>size</c-><c- p>()</c->
          <c- k>requires</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>sized</c-><c- o>&lt;</c-><c- n>First</c-><c- p>,</c-> <c- n>Vs</c-><c- p>...</c-><c- o>></c-><c- p>;</c->
        <c- k>constexpr</c-> <c- o>*</c-><c- n>see</c-> <c- n>below</c-><c- o>*</c-> <c- nf>size</c-><c- p>()</c-> <c- k>const</c->
          <c- k>requires</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>sized</c-><c- o>&lt;</c-><c- k>const</c-> <c- n>First</c-><c- p>,</c-> <c- k>const</c-> <c- n>Vs</c-><c- p>...</c-><c- o>></c-><c- p>;</c->
    <c- p>};</c->

    <c- k>template</c-> <c- o>&lt;</c-><c- n>class</c-><c- p>...</c-> <c- n>Vs</c-><c- o>></c->
    <c- n>cartesian_product_view</c-><c- p>(</c-><c- n>Vs</c-><c- o>&amp;&amp;</c-><c- p>...)</c-><c- o>-></c-><c- n>cartesian_product_view</c-><c- o>&lt;</c-><c- n>all_t</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>;</c->

    <c- k>namespace</c-> <c- n>views</c-> <c- p>{</c-> <c- kr>inline</c-> <c- k>constexpr</c-> <c- n>unspecified</c-> <c- n>cartesian_product</c-> <c- o>=</c-> <c- n>unspecified</c-><c- p>;</c-> <c- p>}</c->
<c- p>}</c->
</pre>
<pre class="highlight"><c- k>constexpr</c-> <c- k>explicit</c-> <c- nf>cartesian_product_view</c-><c- p>(</c-><c- n>First</c-> <c- n>first_base</c-><c- p>,</c-> <c- n>Vs</c-><c- p>...</c-> <c- n>bases</c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Initialises <code class="highlight"><c- n>bases_</c-></code> with <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>move</c-><c- p>(</c-><c- n>first_base</c-><c- p>),</c-> <c- n>std</c-><c- o>::</c-><c- n>move</c-><c- p>(</c-><c- n>bases</c-><c- p>)...</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>constexpr</c-> <c- n>iterator</c-><c- o>&lt;</c->false<c- o>></c-> <c- n>begin</c-><c- p>()</c->
  <c- k>requires</c-> <c- p>(</c-><c- o>!</c-><c- n>simple_view</c-><c- o>&lt;</c-><c- n>First</c-><c- o>></c-> <c- o>||</c-> <c- p>...</c-> <c- o>||</c-> <c- o>!</c-><c- n>simple_view</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to <code class="highlight"><c- k>return</c-> <c- n>iterator</c-><c- o>&lt;</c->false<c- o>></c-><c- p>(</c-><c- n>tuple</c-><c- o>-</c-><c- n>transform</c-><c- p>(</c-><c- n>ranges</c-><c- o>::</c-><c- n>begin</c-><c- p>,</c-> <c- n>bases_</c-><c- p>));</c-></code></p>
   </blockquote>
<pre class="highlight"><c- k>constexpr</c-> <c- n>iterator</c-><c- o>&lt;</c->true<c- o>></c-> <c- n>begin</c-><c- p>()</c->
  <c- k>requires</c-> <c- p>(</c-><c- n>range</c-><c- o>&lt;</c-><c- n>First</c-><c- o>></c-> <c- o>&amp;&amp;</c-> <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>range</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to <code class="highlight"><c- k>return</c-> <c- n>iterator</c-><c- o>&lt;</c->true<c- o>></c-><c- p>(</c-><c- n>tuple</c-><c- o>-</c-><c- n>transform</c-><c- p>(</c-><c- n>ranges</c-><c- o>::</c-><c- n>begin</c-><c- p>,</c-> <c- n>bases_</c-><c- p>));</c-></code></p>
   </blockquote>
<pre class="highlight"><c- k>constexpr</c-> <c- n>iterator</c-><c- o>&lt;</c->false<c- o>></c-> <c- n>end</c-><c- p>()</c->
  <c- k>requires</c-> <c- p>((</c-><c- o>!</c-><c- n>simple_view</c-><c- o>&lt;</c-><c- n>First</c-><c- o>></c-> <c- o>||</c-> <c- p>...</c-> <c- o>||</c-> <c- o>!</c-><c- n>simple_view</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>)</c->
    <c- o>&amp;&amp;</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>common</c-><c- o>&lt;</c-><c- n>First</c-><c- p>,</c-> <c- n>Vs</c-><c- p>...</c-><c- o>></c-><c- p>);</c->
<c- k>constexpr</c-> <c- n>iterator</c-><c- o>&lt;</c->true<c- o>></c-> <c- n>end</c-><c- p>()</c-> <c- k>const</c->
  <c- k>requires</c-><c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>common</c-><c- o>&lt;</c-><c- k>const</c-> <c- n>First</c-><c- p>,</c-> <c- k>const</c-> <c- n>Vs</c-><c- p>...</c-><c- o>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Let <code class="highlight"><c- n>is</c-><c- o>-</c-><c- k>const</c-></code> be <code class="highlight">true</code> for the const-qualified overload, and <code class="highlight">false</code> otherwise. Equivalent to:</p>
<pre class="highlight"><c- n>iterator</c-><c- o>&lt;</c-><c- n>is</c-><c- o>-</c-><c- k>const</c-><c- o>></c-> <c- n>it</c-><c- p>(</c-><c- n>tuple</c-><c- o>-</c-><c- n>transform</c-><c- p>(</c-><c- n>ranges</c-><c- o>::</c-><c- n>begin</c-><c- p>,</c-> <c- n>bases_</c-><c- p>));</c->
<c- n>std</c-><c- o>::</c-><c- n>get</c-><c- o>&lt;</c-><c- mi>0</c-><c- o>></c-><c- p>(</c-><c- n>it</c-><c- p>.</c-><c- n>current_</c-><c- p>)</c-> <c- o>=</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>common</c-><c- o>-</c-><c- n>arg</c-><c- o>-</c-><c- n>end</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>get</c-><c- o>&lt;</c-><c- mi>0</c-><c- o>></c-><c- p>(</c-><c- n>bases_</c-><c- p>));</c->
<c- k>return</c-> <c- n>it</c-><c- p>;</c->
</pre>
   </blockquote>
<pre class="highlight"><c- k>constexpr</c-> <c- n>default_sentinel_t</c-> <c- nf>end</c-><c- p>()</c-> <c- k>const</c->
  <c- k>requires</c-> <c- p>(</c-><c- o>!</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>common</c-><c- o>&lt;</c-><c- k>const</c-> <c- n>First</c-><c- p>,</c-> <c- k>const</c-> <c- n>Vs</c-><c- p>...</c-><c- o>></c-><c- p>)</c-> <c- p>{</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to <code class="highlight"><c- k>return</c-> <c- n>default_sentinel</c-><c- p>;</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>constexpr</c-> <c- o>*</c-><c- n>see</c-> <c- n>below</c-><c- o>*</c-> <c- nf>size</c-><c- p>()</c->
  <c- k>requires</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>sized</c-><c- o>&lt;</c-><c- n>First</c-><c- p>,</c-> <c- n>Vs</c-><c- p>...</c-><c- o>></c-><c- p>;</c->
<c- k>constexpr</c-> <c- o>*</c-><c- n>see</c-> <c- n>below</c-><c- o>*</c-> <c- nf>size</c-><c- p>()</c-> <c- k>const</c->
  <c- k>requires</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>sized</c-><c- o>&lt;</c-><c- k>const</c-> <c- n>First</c-><c- p>,</c-> <c- k>const</c-> <c- n>Vs</c-><c- p>...</c-><c- o>></c-><c- p>;</c->
</pre>
   <blockquote>
    <p>The return type is the smallest unsigned-integer-like type that is sufficiently wide to store the product of the maximum sizes of all underlying ranges. If there is no such type, the type is an implementation-defined unsigned-integer-like type.</p>
   </blockquote>
   <blockquote>
    <p><em>Effects</em>: Returns the product of the size of all ranges in <code class="highlight"><c- n>bases_</c-></code>.</p>
   </blockquote>
   <h4 class="heading settled" data-level="5.3.3" id="class-template-cartesian_product_viewiterator-rangescartesianiterator"><span class="secno">5.3.3. </span><span class="content">Class template <code class="highlight"><c- n>cartesian_product_view</c-><c- o>::</c-><c- n>iterator</c-></code> [ranges.cartesian.iterator]</span><a class="self-link" href="#class-template-cartesian_product_viewiterator-rangescartesianiterator"></a></h4>
<pre class="highlight"><c- k>namespace</c-> <c- n>std</c-><c- o>::</c-><c- n>ranges</c-> <c- p>{</c->
<c- k>template</c-><c- o>&lt;</c-><c- n>input_range</c-> <c- n>First</c-><c- p>,</c-> <c- n>forward_range</c-><c- p>...</c-> <c- n>Vs</c-><c- o>></c->
<c- k>requires</c-> <c- p>(</c-><c- n>view</c-><c- o>&lt;</c-><c- n>First</c-><c- o>></c-> <c- o>&amp;&amp;</c-> <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>view</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>))</c->
<c- k>template</c-><c- o>&lt;</c-><c- b>bool</c-> <c- n>Const</c-><c- o>></c->
<c- k>class</c-> <c- nc>cartesian_product_view</c-><c- o>&lt;</c-><c- n>First</c-><c- p>,</c-> <c- n>Vs</c-><c- p>...</c-><c- o>>::</c-><c- n>iterator</c-> <c- p>{</c->
    <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>cartesian_product_view</c-><c- o>>*</c-> <c- n>parent_</c-><c- p>;</c-> <c- c1>// exposition only</c->
    <c- n>tuple</c-><c- o>-</c-><c- n>or</c-><c- o>-</c-><c- n>pair</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-><c- p>,</c->
      <c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>...</c-><c- o>></c-> <c- n>current_</c-><c- p>{};</c-> <c- c1>// exposition only</c->

    <c- k>template</c-> <c- o>&lt;</c-><c- b>size_t</c-> <c- n>N</c-> <c- o>=</c-> <c- k>sizeof</c-><c- p>...(</c-><c- n>Vs</c-><c- p>)</c-><c- o>></c->
    <c- b>void</c-> <c- n>next</c-><c- p>();</c-> <c- c1>// exposition only</c->

    <c- k>template</c-> <c- o>&lt;</c-><c- b>size_t</c-> <c- n>N</c-> <c- o>=</c-> <c- k>sizeof</c-><c- p>...(</c-><c- n>Vs</c-><c- p>)</c-><c- o>></c->
    <c- b>void</c-> <c- n>prev</c-><c- p>();</c-> <c- c1>// exposition only</c->

    <c- k>template</c-> <c- o>&lt;</c-><c- k>class</c-> <c- nc>Tuple</c-><c- o>></c->
    <c- n>difference_type</c-> <c- n>distance_to</c-><c- p>(</c-><c- n>Tuple</c-> <c- n>t</c-><c- p>);</c-> <c- c1>// exposition only</c->

<c- k>public</c-><c- o>:</c->
    <c- k>using</c-> <c- n>iterator_category</c-> <c- o>=</c-> <c- n>input_iterator_tag</c-><c- p>;</c->
    <c- k>using</c-> <c- n>iterator_concept</c->  <c- o>=</c-> <c- o>*</c-><c- n>see</c-> <c- n>below</c-><c- o>*</c-><c- p>;</c->
    <c- k>using</c-> <c- n>value_type</c-> <c- o>=</c-> <c- n>tuple</c-><c- o>-</c-><c- n>or</c-><c- o>-</c-><c- n>pair</c-><c- o>&lt;</c-><c- n>range_value_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-><c- p>,</c->
      <c- n>range_value_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>...</c-><c- o>></c-><c- p>;</c->
    <c- k>using</c-> <c- n>reference</c-> <c- o>=</c-> <c- n>tuple</c-><c- o>-</c-><c- n>or</c-><c- o>-</c-><c- n>pair</c-><c- o>&lt;</c-><c- n>reference_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-><c- p>,</c->
      <c- n>reference_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>...</c-><c- o>></c-><c- p>;</c->
    <c- k>using</c-> <c- n>difference_type</c-> <c- o>=</c-> <c- o>*</c-><c- n>see</c-> <c- n>below</c-><c- o>*</c-><c- p>;</c->

    <c- n>iterator</c-><c- p>()</c-> <c- o>=</c-> <c- k>default</c-><c- p>;</c->
    <c- k>constexpr</c-> <c- k>explicit</c-> <c- nf>iterator</c-><c- p>(</c-><c- n>tuple</c-><c- o>-</c-><c- n>or</c-><c- o>-</c-><c- n>pair</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-><c- p>,</c->
      <c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>...</c-><c- o>></c-> <c- n>current</c-><c- p>);</c->

    <c- k>constexpr</c-> <c- nf>iterator</c-><c- p>(</c-><c- n>iterator</c-><c- o>&lt;!</c-><c- n>Const</c-><c- o>></c-> <c- n>i</c-><c- p>)</c-> <c- k>requires</c-> <c- n>Const</c-> <c- o>&amp;&amp;</c->
      <c- p>(</c-><c- n>convertible_to</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>First</c-><c- o>></c-><c- p>,</c-> <c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>>></c-> <c- o>&amp;&amp;</c->
        <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>convertible_to</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>,</c-> <c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>>></c-><c- p>);</c->

    <c- k>constexpr</c-> <c- k>auto</c-> <c- k>operator</c-><c- o>*</c-><c- p>()</c-> <c- k>const</c-><c- p>;</c->
    <c- k>constexpr</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>++</c-><c- p>();</c->
    <c- k>constexpr</c-> <c- n>iterator</c-> <c- k>operator</c-><c- o>++</c-><c- p>(</c-><c- b>int</c-><c- p>);</c->

    <c- k>constexpr</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>--</c-><c- p>()</c->
      <c- k>requires</c-> <c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>bidirectional</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>></c-><c- p>,</c->
        <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>);</c->
    <c- k>constexpr</c-> <c- n>iterator</c-> <c- k>operator</c-><c- o>--</c-><c- p>(</c-><c- b>int</c-><c- p>)</c->
      <c- k>requires</c-> <c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>bidirectional</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>></c-><c- p>,</c->
        <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>);</c->

    <c- k>constexpr</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>+=</c-><c- p>(</c-><c- n>difference_type</c-> <c- n>x</c-><c- p>)</c->
      <c- k>requires</c-> <c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>random</c-><c- o>-</c-><c- n>access</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>></c-><c- p>,</c->
        <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>);</c->
    <c- k>constexpr</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>-=</c-><c- p>(</c-><c- n>difference_type</c-> <c- n>x</c-><c- p>)</c->
      <c- k>requires</c-> <c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>random</c-><c- o>-</c-><c- n>access</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>></c-><c- p>,</c->
        <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>);</c->

    <c- k>constexpr</c-> <c- n>reference</c-> <c- k>operator</c-><c- p>[](</c-><c- n>difference_type</c-> <c- n>n</c-><c- p>)</c-> <c- k>const</c->
      <c- k>requires</c-> <c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>random</c-><c- o>-</c-><c- n>access</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>></c-><c- p>,</c->
        <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>);</c->

    <c- k>friend</c-> <c- k>constexpr</c-> <c- b>bool</c-> <c- k>operator</c-><c- o>==</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>y</c-><c- p>)</c->
      <c- k>requires</c-> <c- p>(</c-><c- n>equality_comparable</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>>></c-> <c- o>&amp;&amp;</c->
        <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>equality_comparable</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>>></c-><c- p>);</c->

    <c- k>friend</c-> <c- k>constexpr</c-> <c- b>bool</c-> <c- k>operator</c-><c- o>==</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>std</c-><c- o>::</c-><c- n>default_sentinel_t</c-><c- o>&amp;</c-><c- p>);</c->

    <c- k>friend</c-> <c- k>constexpr</c-> <c- k>auto</c-> <c- k>operator</c-><c- o>&lt;</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>y</c-><c- p>)</c->
      <c- k>requires</c-> <c- p>(</c-><c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-> <c- o>&amp;&amp;</c->
        <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>);</c->
    <c- k>friend</c-> <c- k>constexpr</c-> <c- k>auto</c-> <c- k>operator</c-><c- o>></c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>y</c-><c- p>)</c->
      <c- k>requires</c-> <c- p>(</c-><c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-> <c- o>&amp;&amp;</c->
        <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>);</c->
    <c- k>friend</c-> <c- k>constexpr</c-> <c- k>auto</c-> <c- k>operator</c-><c- o>&lt;=</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>y</c-><c- p>)</c->
      <c- k>requires</c-> <c- p>(</c-><c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-> <c- o>&amp;&amp;</c->
        <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>);</c->
    <c- k>friend</c-> <c- k>constexpr</c-> <c- k>auto</c-> <c- k>operator</c-><c- o>>=</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>y</c-><c- p>)</c->
      <c- k>requires</c-> <c- p>(</c-><c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-> <c- o>&amp;&amp;</c->
        <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>);</c->

    <c- k>friend</c-> <c- k>constexpr</c-> <c- k>auto</c-> <c- k>operator</c-><c- o>&lt;=></c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>y</c-><c- p>)</c->
      <c- k>requires</c-> <c- p>((</c-><c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-> <c- o>&amp;&amp;</c->
        <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>)</c-> <c- o>&amp;&amp;</c->
        <c- p>(</c-><c- n>three_way_comparable</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-> <c- o>&amp;&amp;</c->
        <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>three_way_comparable</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>));</c->

    <c- k>friend</c-> <c- k>constexpr</c-> <c- n>iterator</c-> <c- k>operator</c-><c- o>+</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- n>difference_type</c-> <c- n>y</c-><c- p>)</c->
      <c- k>requires</c-> <c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>random</c-><c- o>-</c-><c- n>access</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>></c-><c- p>,</c->
        <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>);</c->
    <c- k>friend</c-> <c- k>constexpr</c-> <c- n>iterator</c-> <c- k>operator</c-><c- o>+</c-><c- p>(</c-><c- n>difference_type</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>y</c-><c- p>)</c->
      <c- k>requires</c-> <c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>random</c-><c- o>-</c-><c- n>access</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>></c-><c- p>,</c->
        <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>);</c->
    <c- k>friend</c-> <c- k>constexpr</c-> <c- n>iterator</c-> <c- k>operator</c-><c- o>-</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- n>difference_type</c-> <c- n>y</c-><c- p>)</c->
      <c- k>requires</c-> <c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>random</c-><c- o>-</c-><c- n>access</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>></c-><c- p>,</c->
        <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>);</c->
    <c- k>friend</c-> <c- k>constexpr</c-> <c- n>difference_type</c-> <c- k>operator</c-><c- o>-</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>y</c-><c- p>)</c->
      <c- k>requires</c-> <c- p>(</c-><c- n>sized_sentinel_for</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-><c- p>,</c->
          <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-> <c- o>&amp;&amp;</c->
        <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>sized_sentinel_for</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>,</c->
          <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>);</c->

    <c- k>friend</c-> <c- k>constexpr</c-> <c- k>operator</c-><c- o>-</c-><c- p>(</c-><c- n>iterator</c-> <c- n>i</c-><c- p>,</c-> <c- n>default_sentinel_t</c-><c- p>)</c->
      <c- k>requires</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>sentinel</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>sized</c-><c- o>&lt;</c-><c- n>Vs</c-><c- p>...</c-><c- o>></c-><c- p>;</c->
    <c- k>friend</c-> <c- k>constexpr</c-> <c- k>operator</c-><c- o>-</c-><c- p>(</c-><c- n>default_sentinel_t</c-><c- p>,</c-> <c- n>iterator</c-> <c- n>i</c-><c- p>)</c->
      <c- k>requires</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>sentinel</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>sized</c-><c- o>&lt;</c-><c- n>Vs</c-><c- p>...</c-><c- o>></c-><c- p>;</c->

    <c- k>friend</c-> <c- k>constexpr</c-> <c- k>auto</c-> <c- nf>iter_move</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>i</c-><c- p>)</c-> <c- k>noexcept</c-><c- p>(</c-><c- n>see</c-> <c- n>below</c-><c- p>);</c->

    <c- k>friend</c-> <c- k>constexpr</c-> <c- b>void</c-> <c- nf>iter_swap</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>l</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>r</c-><c- p>)</c-> <c- k>noexcept</c-><c- p>(</c-><c- n>see</c-> <c- n>below</c-><c- p>)</c->
        <c- k>requires</c-> <c- p>(</c-><c- n>indirectly_swappable</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>>></c-> <c- o>&amp;&amp;</c-> <c- p>...</c-> <c- o>&amp;&amp;</c->
            <c- n>indirectly_swappable</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Views</c-><c- o>>>></c-><c- p>);</c->
<c- p>};</c->
<c- p>}</c->
</pre>
   <p><code class="highlight"><c- n>iterator</c-><c- o>::</c-><c- n>iterator_concept</c-></code> is defined as follows:</p>
   <ul>
    <li data-md>
     <p>If <code class="highlight"><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>random</c-><c- o>-</c-><c- n>access</c-><c- o>&lt;</c-><c- n>First</c-><c- p>,</c-> <c- n>Vs</c-><c- p>...</c-><c- o>></c-></code> is modeled, then <code class="highlight"><c- n>iterator_concept</c-></code> denotes <code class="highlight"><c- n>random_access_iterator_tag</c-></code>.</p>
    <li data-md>
     <p>Otherwise, if <code class="highlight"><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>bidirectional</c-><c- o>&lt;</c-><c- n>First</c-><c- p>,</c-> <c- n>Vs</c-><c- p>...</c-><c- o>></c-></code> is modeled, then <code class="highlight"><c- n>iterator_concept</c-></code> denotes <code class="highlight"><c- n>bidirectional_iterator_tag</c-></code>.</p>
    <li data-md>
     <p>Otherwise, if <code class="highlight"><c- n>First</c-></code> models <code class="highlight"><c- n>forward_range</c-></code>, then <code class="highlight"><c- n>iterator_concept</c-></code> denotes <code class="highlight"><c- n>forward_iterator_tag</c-></code>.</p>
    <li data-md>
     <p>Otherwise, <code class="highlight"><c- n>iterator_concept</c-></code> denotes <code class="highlight"><c- n>input_iterator_tag</c-></code>.</p>
   </ul>
   <p><code class="highlight"><c- n>iterator</c-><c- o>::</c-><c- n>difference_type</c-></code> is the smallest signed-integer-like type that is sufficiently wide to store the product of the maximum sizes of all underlying ranges. If there is no such type, the type is an implementation-defined signed-integer-like type.</p>
<pre class="highlight"><c- k>template</c-> <c- o>&lt;</c-><c- b>size_t</c-> <c- n>N</c-> <c- o>=</c-> <c- k>sizeof</c-><c- p>...(</c-><c- n>Vs</c-><c- p>)</c-><c- o>></c->
<c- b>void</c-> <c- n>next</c-><c- p>()</c-> <c- c1>// exposition only</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to:</p>
<pre class="highlight"><c- k>auto</c-><c- o>&amp;</c-> <c- n>it</c-> <c- o>=</c-> <c- n>get</c-><c- o>&lt;</c-><c- n>N</c-><c- o>></c-><c- p>(</c-><c- n>current_</c-><c- p>);</c->
<c- o>++</c-><c- n>it</c-><c- p>;</c->
<c- k>if</c-> <c- nf>constexpr</c-> <c- p>(</c-><c- n>N</c-> <c- o>></c-> <c- mi>0</c-><c- p>)</c-> <c- p>{</c->
   <c- k>if</c-> <c- p>(</c-><c- n>it</c-> <c- o>==</c-> <c- n>ranges</c-><c- o>::</c-><c- n>end</c-><c- p>(</c-><c- n>get</c-><c- o>&lt;</c-><c- n>N</c-><c- o>></c-><c- p>(</c-><c- n>parent_</c-><c- o>-></c-><c- n>bases_</c-><c- p>)))</c-> <c- p>{</c->
       <c- n>it</c-> <c- o>=</c-> <c- n>ranges</c-><c- o>::</c-><c- n>begin</c-><c- p>(</c-><c- n>get</c-><c- o>&lt;</c-><c- n>N</c-><c- o>></c-><c- p>(</c-><c- n>parent</c-><c- o>-></c-><c- n>bases_</c-><c- p>));</c->
       <c- n>next</c-><c- o>&lt;</c-><c- n>N</c-> <c- o>-</c-> <c- mi>1</c-><c- o>></c-><c- p>();</c->
   <c- p>}</c->
<c- p>}</c->
</pre>
   </blockquote>
<pre class="highlight"><c- k>template</c-> <c- o>&lt;</c-><c- b>size_t</c-> <c- n>N</c-> <c- o>=</c-> <c- k>sizeof</c-><c- p>...(</c-><c- n>Vs</c-><c- p>)</c-><c- o>></c->
<c- b>void</c-> <c- n>prev</c-><c- p>()</c-> <c- c1>// exposition only</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to:</p>
<pre class="highlight"><c- k>auto</c-><c- o>&amp;</c-> <c- n>it</c-> <c- o>=</c-> <c- n>std</c-><c- o>::</c-><c- n>get</c-><c- o>&lt;</c-><c- n>N</c-><c- o>></c-><c- p>(</c-><c- n>current_</c-><c- p>);</c->
<c- k>if</c-> <c- p>(</c-><c- n>it</c-> <c- o>==</c-> <c- n>std</c-><c- o>::</c-><c- n>ranges</c-><c- o>::</c-><c- n>begin</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>get</c-><c- o>&lt;</c-><c- n>N</c-><c- o>></c-><c- p>(</c-><c- n>parent_</c-><c- o>-></c-><c- n>bases_</c-><c- p>)))</c-> <c- p>{</c->
  <c- n>std</c-><c- o>::</c-><c- n>ranges</c-><c- o>::</c-><c- n>advance</c-><c- p>(</c-><c- n>it</c-><c- p>,</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>common</c-><c- o>-</c-><c- n>arg</c-><c- o>-</c-><c- n>end</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>get</c-><c- o>&lt;</c-><c- n>N</c-><c- o>></c-><c- p>(</c-><c- n>parent_</c-><c- o>-></c-><c- n>bases_</c-><c- p>)));</c->
  <c- k>if</c-> <c- nf>constexpr</c-> <c- p>(</c-><c- n>N</c-> <c- o>></c-> <c- mi>0</c-><c- p>)</c-> <c- p>{</c->
      <c- n>prev</c-><c- o>&lt;</c-><c- n>N</c-> <c- o>-</c-> <c- mi>1</c-><c- o>></c-><c- p>();</c->
  <c- p>}</c->
<c- p>}</c->
<c- o>--</c-><c- n>it</c-><c- p>;</c->
</pre>
   </blockquote>
<pre class="highlight"><c- k>template</c-> <c- o>&lt;</c-><c- k>class</c-> <c- nc>Tuple</c-><c- o>></c->
<c- n>difference_type</c-> <c- n>distance_to</c-><c- p>(</c-><c- n>Tuple</c-> <c- n>t</c-><c- p>);</c-> <c- c1>// exposition only</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Let <code class="highlight"><c- n>scaled_size</c-><c- p>(</c-><c- n>N</c-><c- p>)</c-></code> be <code class="highlight"><c- k>static_cast</c-><c- o>&lt;</c-><c- n>difference_type</c-><c- o>></c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>ranges</c-><c- o>::</c-><c- n>size</c-><c- p>(</c-><c- n>get</c-><c- o>&lt;</c-><c- n>N</c-><c- o>></c-><c- p>(</c-><c- n>parent_</c-><c- o>-></c-><c- n>bases_</c-><c- p>)))</c-> <c- o>*</c-> <c- n>scaled_size</c-><c- p>(</c-><c- n>N</c-><c- o>+</c-><c- mi>1</c-><c- p>)</c-></code> if <code class="highlight"><c- n>N</c-></code> &lt; <code class="highlight"><c- k>sizeof</c-><c- p>...(</c-><c- n>Vs</c-><c- p>)</c-></code>, otherwise <code class="highlight"><c- k>static_cast</c-><c- o>&lt;</c-><c- n>difference_type</c-><c- o>></c-><c- p>(</c-><c- mi>1</c-><c- p>)</c-></code>. Let <code class="highlight"><c- n>scaled_distance</c-><c- p>(</c-><c- n>x</c-><c- p>,</c-> <c- n>y</c-><c- p>,</c-> <c- n>N</c-><c- p>)</c-></code> be <code class="highlight"><c- k>static_cast</c-><c- o>&lt;</c-><c- n>difference_type</c-><c- o>></c-><c- p>(</c-><c- n>get</c-><c- o>&lt;</c-><c- n>N</c-><c- o>></c-><c- p>(</c-><c- n>current_</c-><c- p>)</c-> <c- o>-</c-> <c- n>get</c-><c- o>&lt;</c-><c- n>N</c-><c- o>></c-><c- p>(</c-><c- n>t</c-><c- p>))</c-> <c- o>*</c-> <c- n>scaled_size</c-><c- p>(</c-><c- n>N</c-><c- o>+</c-><c- mi>1</c-><c- p>)</c-></code>. Returns the sum of <code class="highlight"><c- n>scaled_distance</c-><c- p>(</c-><c- n>x</c-><c- p>,</c-> <c- n>y</c-><c- p>,</c-> <c- n>N</c-><c- p>)</c-></code> for every <code class="highlight"><c- n>N</c-></code> in the interval <code class="highlight"><c- p>[</c-><c- mi>0</c-><c- p>,</c-> <c- k>sizeof</c-><c- p>...(</c-><c- n>Vs</c-><c- p>)]</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>constexpr</c-> <c- k>explicit</c-> <c- nf>iterator</c-><c- p>(</c-><c- n>tuple</c-><c- o>-</c-><c- n>or</c-><c- o>-</c-><c- n>pair</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-><c- p>,</c->
  <c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>...</c-><c- o>></c-> <c- n>current</c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Initializes <code class="highlight"><c- n>current_</c-></code> with <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>move</c-><c- p>(</c-><c- n>current</c-><c- p>)</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>constexpr</c-> <c- nf>iterator</c-><c- p>(</c-><c- n>iterator</c-><c- o>&lt;!</c-><c- n>Const</c-><c- o>></c-> <c- n>i</c-><c- p>)</c-> <c- k>requires</c-> <c- n>Const</c-> <c- o>&amp;&amp;</c->
  <c- p>(</c-><c- n>convertible_to</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>First</c-><c- o>></c-><c- p>,</c-> <c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>>></c-> <c- o>&amp;&amp;</c->
    <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>convertible_to</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>Vs</c-><c- o>></c-><c- p>,</c-> <c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Initializes <code class="highlight"><c- n>current_</c-></code> with <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>move</c-><c- p>(</c-><c- n>i</c-><c- p>.</c-><c- n>current_</c-><c- p>)</c-></code>.</p>
   </blockquote>
<pre class="highlight">  <c- k>constexpr</c-> <c- k>auto</c-> <c- k>operator</c-><c- o>*</c-><c- p>()</c-> <c- k>const</c-><c- p>;</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to:</p>
<pre class="highlight"> <c- k>return</c-> <c- n>tuple</c-><c- o>-</c-><c- n>transform</c-><c- p>([](</c-><c- k>auto</c-><c- o>&amp;</c-> <c- n>i</c-><c- p>)</c-> <c- o>-></c-> <c- k>decltype</c-><c- p>(</c-><c- k>auto</c-><c- p>)</c-> <c- p>{</c-> <c- k>return</c-> <c- o>*</c-><c- n>i</c-><c- p>;</c-> <c- p>},</c-> <c- n>current_</c-><c- p>);</c->
</pre>
   </blockquote>
<pre class="highlight"><c- k>constexpr</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>++</c-><c- p>();</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to:</p>
<pre class="highlight"><c- n>next</c-><c- p>();</c->
<c- k>return</c-> <c- o>*</c-><c- k>this</c-><c- p>;</c->
</pre>
   </blockquote>
<pre class="highlight"><c- k>constexpr</c-> <c- n>iterator</c-> <c- k>operator</c-><c- o>++</c-><c- p>(</c-><c- b>int</c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to:</p>
<pre class="highlight"><c- k>auto</c-> <c- n>tmp</c-> <c- o>=</c-> <c- o>*</c-><c- k>this</c-><c- p>;</c->
<c- o>++*</c-><c- k>this</c-><c- p>;</c->
<c- k>return</c-> <c- n>tmp</c-><c- p>;</c->
</pre>
   </blockquote>
<pre class="highlight"><c- k>constexpr</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>--</c-><c- p>()</c->
  <c- k>requires</c-> <c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>bidirectional</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>></c-><c- p>,</c->
    <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to:</p>
<pre class="highlight"><c- n>prev</c-><c- p>();</c->
<c- k>return</c-> <c- o>*</c-><c- k>this</c-><c- p>;</c->
</pre>
   </blockquote>
<pre class="highlight"><c- k>constexpr</c-> <c- n>iterator</c-> <c- k>operator</c-><c- o>--</c-><c- p>(</c-><c- b>int</c-><c- p>)</c->
  <c- k>requires</c-> <c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>bidirectional</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>></c-><c- p>,</c->
    <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to:</p>
<pre class="highlight"><c- k>auto</c-> <c- n>tmp</c-> <c- o>=</c-> <c- o>*</c-><c- k>this</c-><c- p>;</c->
<c- o>--*</c-><c- k>this</c-><c- p>;</c->
<c- k>return</c-> <c- n>tmp</c-><c- p>;</c->
</pre>
   </blockquote>
<pre class="highlight"><c- k>constexpr</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>+=</c-><c- p>(</c-><c- n>difference_type</c-> <c- n>x</c-><c- p>)</c->
  <c- k>requires</c-> <c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>random</c-><c- o>-</c-><c- n>access</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>></c-><c- p>,</c->
    <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Sets the position of the iterators in <code class="highlight"><c- n>current_</c-></code>:</p>
    <ul>
     <li data-md>
      <p>If <code class="highlight"><c- n>x</c-> <c- o>></c-> <c- mi>0</c-></code>, as if <code class="highlight"><c- n>next</c-></code> was called <code class="highlight"><c- n>x</c-></code> times.</p>
     <li data-md>
      <p>Otherwise, if <code class="highlight"><c- n>x</c-> <c- o>&lt;</c-> <c- mi>0</c-></code>, as if <code class="highlight"><c- n>prev</c-></code> was called <code class="highlight"><c- o>-</c-><c- n>x</c-></code> times.</p>
     <li data-md>
      <p>Otherwise, no effect.</p>
    </ul>
    <p><em>Complexity</em>: Constant.</p>
   </blockquote>
<pre class="highlight"><c- k>constexpr</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- k>operator</c-><c- o>-=</c-><c- p>(</c-><c- n>difference_type</c-> <c- n>x</c-><c- p>)</c->
  <c- k>requires</c-> <c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>random</c-><c- o>-</c-><c- n>access</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>></c-><c- p>,</c->
    <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to:</p>
<pre class="highlight"><c- o>*</c-><c- k>this</c-> <c- o>+=</c-> <c- o>-</c-><c- n>x</c-><c- p>;</c->
<c- k>return</c-> <c- o>*</c-><c- k>this</c-><c- p>;</c->
</pre>
   </blockquote>
<pre class="highlight"><c- k>constexpr</c-> <c- n>reference</c-> <c- k>operator</c-><c- p>[](</c-><c- n>difference_type</c-> <c- n>n</c-><c- p>)</c-> <c- k>const</c->
  <c- k>requires</c-> <c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>random</c-><c- o>-</c-><c- n>access</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>></c-><c- p>,</c->
    <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to <code class="highlight"><c- k>return</c-> <c- o>*</c-><c- p>((</c-><c- o>*</c-><c- k>this</c-><c- p>)</c-> <c- o>+</c-> <c- n>n</c-><c- p>);</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>friend</c-> <c- k>constexpr</c-> <c- b>bool</c-> <c- k>operator</c-><c- o>==</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>y</c-><c- p>)</c->
  <c- k>requires</c-> <c- p>(</c-><c- n>equality_comparable</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>>></c-> <c- o>&amp;&amp;</c->
    <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>equality_comparable</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to <code class="highlight"><c- k>return</c-> <c- n>x</c-><c- p>.</c-><c- n>current_</c-> <c- o>==</c-> <c- n>y</c-><c- p>.</c-><c- n>current_</c-><c- p>;</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>friend</c-> <c- k>constexpr</c-> <c- b>bool</c-> <c- k>operator</c-><c- o>==</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>std</c-><c- o>::</c-><c- n>default_sentinel_t</c-><c- o>&amp;</c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to <code class="highlight"><c- k>return</c-> <c- n>std</c-><c- o>::</c-><c- n>get</c-><c- o>&lt;</c-><c- mi>0</c-><c- o>></c-><c- p>(</c-><c- n>x</c-><c- p>.</c-><c- n>current_</c-><c- p>)</c-> <c- o>==</c-> <c- n>std</c-><c- o>::</c-><c- n>ranges</c-><c- o>::</c-><c- n>end</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>get</c-><c- o>&lt;</c-><c- mi>0</c-><c- o>></c-><c- p>(</c-><c- n>x</c-><c- p>.</c-><c- n>parent_</c-><c- o>-></c-><c- n>bases_</c-><c- p>));</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>friend</c-> <c- k>constexpr</c-> <c- k>auto</c-> <c- k>operator</c-><c- o>&lt;</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>y</c-><c- p>)</c->
  <c- k>requires</c-> <c- p>(</c-><c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-> <c- o>&amp;&amp;</c->
    <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to <code class="highlight"><c- k>return</c-> <c- n>x</c-><c- p>.</c-><c- n>current_</c-> <c- o>&lt;</c-> <c- n>y</c-><c- p>.</c-><c- n>current_</c-><c- p>;</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>friend</c-> <c- k>constexpr</c-> <c- k>auto</c-> <c- k>operator</c-><c- o>></c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>y</c-><c- p>)</c->
  <c- k>requires</c-> <c- p>(</c-><c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-> <c- o>&amp;&amp;</c->
    <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to <code class="highlight"><c- k>return</c-> <c- n>y</c-> <c- o>&lt;</c-> <c- n>x</c-><c- p>;</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>friend</c-> <c- k>constexpr</c-> <c- k>auto</c-> <c- k>operator</c-><c- o>&lt;=</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>y</c-><c- p>)</c->
  <c- k>requires</c-> <c- p>(</c-><c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-> <c- o>&amp;&amp;</c->
    <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to <code class="highlight"><c- k>return</c-> <c- o>!</c-><c- p>(</c-><c- n>y</c-> <c- o>&lt;</c-> <c- n>x</c-><c- p>);</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>friend</c-> <c- k>constexpr</c-> <c- k>auto</c-> <c- k>operator</c-><c- o>>=</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>y</c-><c- p>)</c->
  <c- k>requires</c-> <c- p>(</c-><c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-> <c- o>&amp;&amp;</c->
    <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to <code class="highlight"><c- k>return</c-> <c- o>!</c-><c- p>(</c-><c- n>x</c-> <c- o>&lt;</c-> <c- n>y</c-><c- p>);</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>friend</c-> <c- k>constexpr</c-> <c- k>auto</c-> <c- k>operator</c-><c- o>&lt;=></c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>y</c-><c- p>)</c->
  <c- k>requires</c-> <c- p>((</c-><c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-> <c- o>&amp;&amp;</c->
    <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>random_access_range</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>)</c-> <c- o>&amp;&amp;</c->
    <c- p>(</c-><c- n>three_way_comparable</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-> <c- o>&amp;&amp;</c->
    <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>three_way_comparable</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>));</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to <code class="highlight"><c- k>return</c-> <c- n>x</c-><c- p>.</c-><c- n>current_</c-> <c- o>&lt;=></c-> <c- n>y</c-><c- p>.</c-><c- n>current_</c-><c- p>;</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>friend</c-> <c- k>constexpr</c-> <c- n>iterator</c-> <c- k>operator</c-><c- o>+</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- n>difference_type</c-> <c- n>y</c-><c- p>)</c->
  <c- k>requires</c-> <c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>random</c-><c- o>-</c-><c- n>access</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>></c-><c- p>,</c->
    <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to <code class="highlight"><c- k>return</c-> <c- n>iterator</c-><c- p>{</c-> <c- n>x</c-> <c- p>}</c-> <c- o>+=</c-> <c- n>y</c-><c- p>;</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>friend</c-> <c- k>constexpr</c-> <c- n>iterator</c-> <c- k>operator</c-><c- o>+</c-><c- p>(</c-><c- n>difference_type</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>y</c-><c- p>)</c->
  <c- k>requires</c-> <c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>random</c-><c- o>-</c-><c- n>access</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>></c-><c- p>,</c->
    <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to <code class="highlight"><c- k>return</c-> <c- n>y</c-> <c- o>+</c-> <c- n>x</c-><c- p>;</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>friend</c-> <c- k>constexpr</c-> <c- n>iterator</c-> <c- k>operator</c-><c- o>-</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- n>difference_type</c-> <c- n>y</c-><c- p>)</c->
  <c- k>requires</c-> <c- p>(</c-><c- n>cartesian</c-><c- o>-</c-><c- n>product</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>random</c-><c- o>-</c-><c- n>access</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>></c-><c- p>,</c->
    <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>></c-><c- p>...</c-><c- o>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to <code class="highlight"><c- k>return</c-> <c- n>iterator</c-><c- p>{</c-> <c- n>x</c-> <c- p>}</c-> <c- o>-=</c-> <c- n>y</c-><c- p>;</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>friend</c-> <c- k>constexpr</c-> <c- n>difference_type</c-> <c- k>operator</c-><c- o>-</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>x</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>y</c-><c- p>)</c->
  <c- k>requires</c-> <c- p>(</c-><c- n>sized_sentinel_for</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-><c- p>,</c->
      <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>></c-> <c- o>&amp;&amp;</c->
    <c- p>...</c-> <c- o>&amp;&amp;</c-> <c- n>sized_sentinel_for</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>,</c->
      <c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Vs</c-><c- o>>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to <code class="highlight"><c- k>return</c-> <c- n>x</c-><c- p>.</c-><c- n>distance_to</c-><c- p>(</c-><c- n>y</c-><c- p>.</c-><c- n>current_</c-><c- p>);</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>friend</c-> <c- k>constexpr</c-> <c- k>operator</c-><c- o>-</c-><c- p>(</c-><c- n>iterator</c-> <c- n>i</c-><c- p>,</c-> <c- n>default_sentinel_t</c-><c- p>)</c->
  <c- k>requires</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>sentinel</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>sized</c-><c- o>&lt;</c-><c- n>Vs</c-><c- p>...</c-><c- o>></c-><c- p>;</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Let <code class="highlight"><c- n>end</c-><c- o>-</c-><c- n>tuple</c-></code> be an object of a type that is a specialization of <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>tuple</c-></code>, such that:</p>
    <ul>
     <li data-md>
      <p><code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>get</c-><c- o>&lt;</c-><c- mi>0</c-><c- o>></c-><c- p>(</c-><c- n>end</c-><c- o>-</c-><c- n>tuple</c-><c- p>)</c-></code> has the same value as <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>ranges</c-><c- o>::</c-><c- n>end</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>get</c-><c- o>&lt;</c-><c- mi>0</c-><c- o>></c-><c- p>(</c-><c- n>i</c-><c- p>.</c-><c- n>parent_</c-><c- o>-></c-><c- n>bases_</c-><c- p>))</c-></code>;</p>
     <li data-md>
      <p><code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>get</c-><c- o>&lt;</c-><c- n>N</c-><c- o>></c-><c- p>(</c-><c- n>end</c-><c- o>-</c-><c- n>tuple</c-><c- p>)</c-></code> has the same value as <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>ranges</c-><c- o>::</c-><c- n>begin</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>get</c-><c- o>&lt;</c-><c- n>N</c-><c- o>></c-><c- p>(</c-><c- n>i</c-><c- p>.</c-><c- n>parent_</c-><c- o>-></c-><c- n>bases_</c-><c- p>))</c-></code> for every <code class="highlight"><c- n>N</c-></code> in the interval <code class="highlight"><c- p>[</c-><c- mi>1</c-><c- p>,</c-> <c- k>sizeof</c-><c- p>...(</c-><c- n>Vs</c-><c- p>)</c-> <c- o>+</c-> <c- mi>1</c-><c- p>)</c-></code>.</p>
    </ul>
    <p>Equivalent to: <code class="highlight"><c- k>return</c-> <c- n>i</c-><c- p>.</c-><c- n>distance_to</c-><c- p>(</c-><c- n>end</c-><c- o>-</c-><c- n>tuple</c-><c- p>);</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>friend</c-> <c- k>constexpr</c-> <c- k>operator</c-><c- o>-</c-><c- p>(</c-><c- n>default_sentinel_t</c-> <c- n>s</c-><c- p>,</c-> <c- n>iterator</c-> <c- n>i</c-><c- p>)</c->
  <c- k>requires</c-> <c- n>cartesian</c-><c- o>-</c-><c- n>sentinel</c-><c- o>-</c-><c- n>is</c-><c- o>-</c-><c- n>sized</c-><c- o>&lt;</c-><c- n>Vs</c-><c- p>...</c-><c- o>></c-><c- p>;</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to <code class="highlight"><c- k>return</c-> <c- o>-</c-><c- p>(</c-><c- n>i</c-> <c- o>-</c-> <c- n>s</c-><c- p>);</c-></code>.</p>
   </blockquote>
<pre class="highlight"><c- k>friend</c-> <c- k>constexpr</c-> <c- k>auto</c-> <c- nf>iter_move</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>i</c-><c- p>)</c-> <c- k>noexcept</c-><c- p>(</c-><c- n>see</c-> <c- n>below</c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: Equivalent to: <code class="highlight"><c- k>return</c-> <c- n>tuple</c-><c- o>-</c-><c- n>transform</c-><c- p>(</c-><c- n>ranges</c-><c- o>::</c-><c- n>iter_move</c-><c- p>,</c-> <c- n>i</c-><c- p>.</c-><c- n>current_</c-><c- p>);</c-></code>.</p>
   </blockquote>
   <blockquote>
    <p><em>Remarks</em>: The exception specification is equivalent to:</p>
<pre class="highlight"><c- p>(</c-><c- k>noexcept</c-><c- p>(</c-><c- n>ranges</c-><c- o>::</c-><c- n>iter_move</c-><c- p>(</c-><c- n>declval</c-><c- o>&lt;</c-><c- k>const</c-> <c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>>&amp;></c-><c- p>()))</c-> <c- o>&amp;&amp;</c-> <c- p>...</c-> <c- o>&amp;&amp;</c->
   <c- k>noexcept</c-><c- p>(</c-><c- n>ranges</c-><c- o>::</c-><c- n>iter_move</c-><c- p>(</c-><c- n>declval</c-><c- o>&lt;</c-><c- k>const</c-> <c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Views</c-><c- o>>>&amp;></c-><c- p>())))</c-> <c- o>&amp;&amp;</c->
<c- p>(</c-><c- n>is_nothrow_move_constructible_v</c-><c- o>&lt;</c-><c- n>range_rvalue_reference_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>>></c-> <c- o>&amp;&amp;</c-> <c- p>...</c-> <c- o>&amp;&amp;</c->
   <c- n>is_nothrow_move_constructible_v</c-><c- o>&lt;</c-><c- n>range_rvalue_reference_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Views</c-><c- o>>>></c-><c- p>)</c->
</pre>
   </blockquote>
<pre class="highlight"><c- k>friend</c-> <c- k>constexpr</c-> <c- b>void</c-> <c- nf>iter_swap</c-><c- p>(</c-><c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>l</c-><c- p>,</c-> <c- k>const</c-> <c- n>iterator</c-><c- o>&amp;</c-> <c- n>r</c-><c- p>)</c-> <c- k>noexcept</c-><c- p>(</c-><c- n>see</c-> <c- n>below</c-><c- p>)</c->
    <c- k>requires</c-> <c- p>(</c-><c- n>indirectly_swappable</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>First</c-><c- o>>>></c-> <c- o>&amp;&amp;</c-> <c- p>...</c-> <c- o>&amp;&amp;</c->
        <c- n>indirectly_swappable</c-><c- o>&lt;</c-><c- n>iterator_t</c-><c- o>&lt;</c-><c- n>maybe</c-><c- o>-</c-><c- k>const</c-><c- o>&lt;</c-><c- n>Const</c-><c- p>,</c-> <c- n>Views</c-><c- o>>>></c-><c- p>);</c->
</pre>
   <blockquote>
    <p><em>Effects</em>: For every integer 0 ≤ i &lt; <code class="highlight"><c- k>sizeof</c-><c- p>...(</c-><c- n>Views</c-><c- p>)</c-> <c- o>+</c-> <c- mi>1</c-></code>, performs: <code class="highlight"><c- n>ranges</c-><c- o>::</c-><c- n>iter_swap</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>get</c-><c- o>&lt;</c-><c- n>i</c-><c- o>></c-><c- p>(</c-><c- n>l</c-><c- p>.</c-><c- n>current_</c-><c- p>),</c-> <c- n>std</c-><c- o>::</c-><c- n>get</c-><c- o>&lt;</c-><c- n>i</c-><c- o>></c-><c- p>(</c-><c- n>r</c-><c- p>.</c-><c- n>current_</c-><c- p>))</c-></code>.</p>
   </blockquote>
   <blockquote>
    <p><em>Remarks</em>: The exception specification is equivalent to the logical AND of the following expressions: <code class="highlight"><c- k>noexcept</c-><c- p>(</c-><c- n>ranges</c-><c- o>::</c-><c- n>iter_swap</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>get</c-><c- o>&lt;</c-><c- n>i</c-><c- o>></c-><c- p>(</c-><c- n>l</c-><c- p>.</c-><c- n>current_</c-><c- p>),</c-> <c- n>std</c-><c- o>::</c-><c- n>get</c-><c- o>&lt;</c-><c- n>i</c-><c- o>></c-><c- p>(</c-><c- n>r</c-><c- p>.</c-><c- n>current_</c-><c- p>)))</c-></code> for every integer 0 ≤ i &lt; <code class="highlight"><c- k>sizeof</c-><c- p>...(</c-><c- n>Views</c-><c- p>)</c-> <c- o>+</c-> <c- mi>1</c-></code>.</p>
   </blockquote>
   <h3 class="heading settled" data-level="5.4" id="feature-test-macro"><span class="secno">5.4. </span><span class="content">Feature-test macro</span><a class="self-link" href="#feature-test-macro"></a></h3>
   <p>Add the following macro definition to 17.3.2 [version.syn], Header <code class="highlight"><c- o>&lt;</c-><c- n>version</c-><c- o>></c-></code> synopsis, with the value selected by the editor to reflect the date of adoption of this paper:</p>
<pre class="highlight"><c- cp>#define __cpp_lib_ranges_cartesian_product 20XXXXL </c-><c- c1>// also in &lt;ranges></c->
</pre>
   <h2 class="heading settled" data-level="6" id="acknowledgements"><span class="secno">6. </span><span class="content">Acknowledgements</span><a class="self-link" href="#acknowledgements"></a></h2>
   <p>Thank you to Christopher Di Bella, Corentin Jabot, Tim Song, and Barry Revzin for feedback and guidance.</p>
   <p>Thank you to Tomasz Kamiński for help with getting the wording into a good shape.</p>
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