<!doctype html><html lang="en">
 <head>
  <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
  <meta content="width=device-width, initial-scale=1, shrink-to-fit=no" name="viewport">
  <title>P2299R4: mdspans of All Dynamic Extents</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,
	#profile-and-date {
		/* #profile-and-date 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: underline #707070;
		text-decoration: underline var(--a-normal-underline);
		text-decoration-skip-ink: none;
	}
	a:visited {
		color: #034575;
		color: var(--a-visited-text);
		text-decoration-color: #bbb;
		text-decoration-color: var(--a-visited-underline);
	}

	/* Indicate interaction with the link */
	a[href]:focus,
	a[href]:hover {
		text-decoration-thickness: 2px;
	}
	a[href]:active {
		color: #c00;
		color: var(--a-active-text);
		text-decoration-color: #c00;
		text-decoration-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: 0.1rem 1px 0;
		/* Larger, more consistently-sized click target */
		display: block;
		/* Switch to using border-bottom for underlines */
		text-decoration: none;
		border-bottom: 1px solid;
		/* 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:focus,
	.toc a:hover {
		background: rgba(75%, 75%, 75%, .25);
		background: var(--a-hover-bg);
		border-bottom-width: 3px;
		margin-bottom: -2px;
	}
	.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;
			border-bottom: 3px solid transparent;
			margin-bottom: -3px;
		}
		#toc .content:hover,
		#toc .content:focus {
			background: rgba(75%, 75%, 75%, .25);
			background: var(--a-hover-bg);
			border-bottom-color: #054572;
			border-bottom-color: var(--toclink-underline);
		}
		#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 a + span {
			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>
    table, th, td {
      border: 1px solid black;
      border-collapse: collapse;
      vertical-align: top;
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    th, td {
      border-left: none;
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      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 */
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    blockquote c-[m] { color: inherit; } /* Literal.Number */
    blockquote c-[n] { color: inherit; } /* Name */
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    blockquote c-[s] { color: inherit; } /* Literal.String */
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    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 */
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    blockquote c-[ni] { color: inherit; } /* Name.Entity */
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    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 d5d58a306, updated Fri Jan 26 16:12:28 2024 -0800" name="generator">
  <link href="https://wg21.link/P2299" rel="canonical">
  <link href="https://isocpp.org/favicon.ico" rel="icon">
  <meta content="46326b4b2ac3c2fbeb5fd6a1171d2a40a12ac0b7" name="revision">
<style>
table {
  border: none !important;
}
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 <body class="h-entry">
  <div class="head">
   <p data-fill-with="logo"></p>
   <h1 class="p-name no-ref" id="title">P2299R4<br><code class="highlight"><c- n>mdspan</c-></code> of All Dynamic Extents</h1>
   <h2 class="no-num no-toc no-ref heading settled" id="profile-and-date"><span class="content">Published Proposal, <time class="dt-updated" datetime="2024-02-15">2024-02-15</time></span></h2>
   <div data-fill-with="spec-metadata">
    <dl>
     <dt class="editor">Author:
     <dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:brycelelbach@gmail.com">Bryce Adelstein Lelbach (he/him/his) — Library Evolution Chair</a> (<span class="p-org org">NVIDIA</span>)
     <dt>Source:
     <dd><a href="https://github.com/brycelelbach/wg21_p2299_mdspans_of_all_dynamic_extents/blob/main/mdspans_of_all_dynamic_extents.bs">GitHub</a>
     <dt>Issue Tracking:
     <dd><a href="https://github.com/brycelelbach/wg21_p2299_mdspans_of_all_dynamic_extents/issues">GitHub</a>
     <dt>Project:
     <dd>ISO/IEC 14882 Programming Languages — C++, ISO/IEC JTC1/SC22/WG21
     <dt>Audience:
     <dd>WG21
    </dl>
   </div>
   <div data-fill-with="warning"></div>
   <hr title="Separator for header">
  </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="#introduction"><span class="secno">1</span> <span class="content">Introduction</span></a>
    <li><a href="#ctad"><span class="secno">2</span> <span class="content">Class Template Argument Deduction for All Dynamic Extents</span></a>
    <li><a href="#template-alias"><span class="secno">3</span> <span class="content">Template Aliases for All Dynamic Extents</span></a>
    <li><a href="#convenience-alias"><span class="secno">4</span> <span class="content">Remove <code class="highlight"><c- n>mdspan</c-></code> Convenience Alias</span></a>
    <li><a href="#wording"><span class="secno">5</span> <span class="content">Wording</span></a>
    <li>
     <a href="#references"><span class="secno"></span> <span class="content">References</span></a>
     <ol class="toc">
      <li><a href="#informative"><span class="secno"></span> <span class="content">Informative References</span></a>
     </ol>
   </ol>
  </nav>
  <main>
   <h2 class="heading settled" data-level="1" id="introduction"><span class="secno">1. </span><span class="content">Introduction</span><a class="self-link" href="#introduction"></a></h2>
   <p><a data-link-type="biblio" href="#biblio-p0009r12" title="MDSPAN">[P0009R12]</a> proposes adding non-owning multidimensional span abstractions
  to the C++ Standard Library; <code class="highlight"><c- n>basic_mdspan</c-></code>, which is fully generic and
  can represent any kind of multidimensional data, and <code class="highlight"><c- n>mdspan</c-></code>, a
  convenience template alias for simpler use cases.</p>
<pre class="highlight"><c- k>template</c-> <c- o>&lt;</c-><c- k>class</c-> <c- nc>ElementType</c-><c- p>,</c-> <c- k>class</c-> <c- nc>Extents</c-><c- p>,</c-> <c- k>class</c-> <c- nc>LayoutPolicy</c-> <c- o>=</c-> <c- n>layout_right</c-><c- p>,</c->
          <c- k>class</c-> <c- nc>AccessorPolicy</c-> <c- o>=</c-> <c- n>accessor_basic</c-><c- o>&lt;</c-><c- n>ElementType</c-><c- o>>></c->
<c- k>struct</c-> <c- nc>basic_mdspan</c-><c- p>;</c->

<c- k>template</c-> <c- o>&lt;</c-><c- k>class</c-> <c- nc>ElementType</c-><c- p>,</c-> <c- b>size_t</c-><c- p>...</c-> <c- n>Extents</c-><c- o>></c->
<c- k>using</c-> <c- n>mdspan</c-> <c- o>=</c-> <c- n>basic_mdspan</c-><c- o>&lt;</c-><c- n>ElementType</c-><c- p>,</c-> <c- n>extents</c-><c- o>&lt;</c-><c- n>Extents</c-><c- p>...</c-><c- o>>></c-><c- p>;</c->
</pre>
   <p>In the <code class="highlight"><c- n>basic_mdspan</c-></code>/<code class="highlight"><c- n>span</c-></code> interface, extents can be either static, e.g.
  expressed at compile time:</p>
<pre class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- b>double</c-><c- p>,</c-> <c- mi>64</c-><c- p>,</c-> <c- mi>64</c-><c- o>></c-> <c- n>a</c-><c- p>(</c-><c- n>data</c-><c- p>);</c->
</pre>
   <p>or dynamic, e.g. expressed at run time:</p>
<pre class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- b>double</c-><c- p>,</c-> <c- n>dynamic_extent</c-><c- p>,</c-> <c- n>dynamic_extent</c-><c- o>></c-> <c- n>a</c-><c- p>(</c-><c- n>data</c-><c- p>,</c-> <c- mi>64</c-><c- p>,</c-> <c- mi>64</c-><c- p>);</c->
</pre>
   <p>You can also use a mix of the two styles:</p>
<pre class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- b>double</c-><c- p>,</c-> <c- mi>64</c-><c- p>,</c-> <c- n>dynamic_extent</c-><c- o>></c-> <c- n>a</c-><c- p>(</c-><c- n>data</c-><c- p>,</c-> <c- mi>64</c-><c- p>);</c->
</pre>
   <p>While <code class="highlight"><c- n>basic_mdspan</c-></code> and <code class="highlight"><c- n>mdspan</c-></code> are powerful, the spelling of instantiations
  can be verbose, especially for the common case where all extents are dynamic.</p>
   <h2 class="heading settled" data-level="2" id="ctad"><span class="secno">2. </span><span class="content">Class Template Argument Deduction for All Dynamic Extents</span><a class="self-link" href="#ctad"></a></h2>
   <p>Using class template argument deduction (introduced in C++17) and alias
  template argument deduction (introduced in C++20), we can make it a easier to
  use <code class="highlight"><c- n>mdspan</c-></code> with all dynamic extents:</p>
   <table>
    <tbody>
     <tr>
      <th>Before 
      <th>After 
     <tr>
      <td><code class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- b>double</c-><c- p>,</c-> <c- n>dynamic_extent</c-><c- p>,</c-> <c- n>dynamic_extent</c-><c- o>></c-> <c- n>a</c-><c- p>(</c-><c- n>data</c-><c- p>,</c-> <c- mi>64</c-><c- p>,</c-> <c- mi>64</c-><c- p>);</c-></code> 
      <td><code class="highlight"><c- n>mdspan</c-> <c- nf>a</c-><c- p>(</c-><c- n>data</c-><c- p>,</c-> <c- mi>64</c-><c- p>,</c-> <c- mi>64</c-><c- p>);</c-></code> 
   </table>
   <p>To make this work, we need to add a deduction guide for <code class="highlight"><c- n>basic_mdspan</c-></code>.
Through the power of alias template argument deduction, <code class="highlight"><c- n>mdspan</c-></code> will be
  able to use said deduction guide as well.</p>
   <p>Here’s <a href="https://godbolt.org/z/6xhb64xTG">an example</a> implementation of such a
  deduction guide for <code class="highlight"><c- n>basic_mdspan</c-></code>.</p>
   <p>In earlier versions of this paper, it was unclear whether such a deduction
  guide would work for the alias template <code class="highlight"><c- n>mdspan</c-></code>, as attempts to construct
  one that functioned as intended had failed.
However, we have since learned that the this is due to bugs in the two
  implementations that currently support alias template deduction, MSVC
  and GCC.
Those bugs have been reported to the respective compilers and hopefully
  will be fixed soon.</p>
   <p>Here’s <a href="https://godbolt.org/z/jnWqbGr1o">an example</a> of the current
  implementation bugs that prevent the deduction guide from working for <code class="highlight"><c- n>mdspan</c-></code>.</p>
   <h2 class="heading settled" data-level="3" id="template-alias"><span class="secno">3. </span><span class="content">Template Aliases for All Dynamic Extents</span><a class="self-link" href="#template-alias"></a></h2>
   <p>The root of the interface challenge here is the heterogeneous nature of extents
  in <code class="highlight"><c- n>mdspan</c-></code>.
When you need to express static extents or a mix of static and dynamic extents,
  we must state the kind of every extent, similar to how we state the type of
  every element of a <code class="highlight"><c- n>tuple</c-></code>.
This heterogenity gives us flexibility at the cost of verbosity.</p>
   <p>However, in the case of all dynamic extents, we do not need that flexibility;
  the kind of every extent is the same.
Instead of a <code class="highlight"><c- n>tuple</c-></code>-like interface, we likely want an <code class="highlight"><c- n>array</c-></code>-like interface,
  where we can simple state the number of extents, instead of listing every one.</p>
   <p>We can provide this simplified interface easily by adding a template alias for <code class="highlight"><c- n>extents</c-></code> that takes the number of extents as a parameter and expands to an <code class="highlight"><c- n>extents</c-></code> of that many <code class="highlight"><c- n>dynamic_extents</c-></code>.
Here’s <a href="https://godbolt.org/z/ahjWjeE4f">an example</a> implementation.</p>
   <table>
    <tbody>
     <tr>
      <th><code class="highlight"><c- n>tuple</c-></code>-like 
      <th><code class="highlight"><c- n>array</c-></code>-like 
     <tr>
      <td><code class="highlight"><c- n>tuple</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>T</c-><c- p>,</c-> <c- n>T</c-><c- o>></c-></code> 
      <td><code class="highlight"><c- n>array</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- mi>3</c-><c- o>></c-></code> 
     <tr>
      <td><code class="highlight"><c- n>extents</c-><c- o>&lt;</c-><c- n>dynamic_extent</c-><c- p>,</c-> <c- n>dynamic_extent</c-><c- p>,</c-> <c- n>dynamic_extent</c-><c- o>></c-> </code>
      <td><code class="highlight"><c- n>dextents</c-><c- o>&lt;</c-><c- mi>3</c-><c- o>></c-> <b><c- p>(</c-><c- n>proposed</c-><c- p>)</c-></b> </code>
   </table>
   <p>If you are working with an <code class="highlight"><c- n>array</c-></code>-like representation of extents, working with <code class="highlight"><c- n>mdspan</c-></code> can become quite awkward:</p>
<pre class="highlight"><c- k>template</c-> <c- o>&lt;</c-><c- b>size_t</c-><c- o>></c->
<c- k>constexpr</c-> <c- k>auto</c-> <c- n>make_dynamic_extent</c-><c- p>()</c-> <c- p>{</c->
  <c- k>return</c-> <c- n>dynamic_extent</c-><c- p>;</c->
<c- p>}</c->

<c- k>template</c-> <c- o>&lt;</c-><c- k>typename</c-> <c- nc>T</c-><c- p>,</c-> <c- b>size_t</c-> <c- n>Rank</c-><c- o>></c->
<c- k>struct</c-> <c- nc>tensor</c-> <c- p>{</c->
  <c- n>T</c-><c- o>*</c-> <c- n>data</c-><c- p>;</c->
  <c- n>array</c-><c- o>&lt;</c-><c- b>size_t</c-><c- p>,</c-> <c- n>Rank</c-><c- o>></c-> <c- n>extents</c-><c- p>;</c->

  <c- k>auto</c-> <c- n>get_mdspan</c-><c- p>()</c-> <c- p>{</c->
    <c- k>return</c-> <c- n>get_mdspan_impl</c-><c- p>(</c-><c- n>make_index_sequence</c-><c- o>&lt;</c-><c- n>Rank</c-><c- o>></c-><c- p>());</c->
  <c- p>}</c->

  <c- k>template</c-> <c- o>&lt;</c-><c- b>size_t</c-><c- p>...</c-> <c- n>Pack</c-><c- o>></c->
  <c- k>auto</c-> <c- n>get_mdspan_impl</c-><c- p>(</c-><c- n>index_sequence</c-><c- o>&lt;</c-><c- n>Pack</c-><c- p>...</c-><c- o>></c-><c- p>)</c-> <c- p>{</c->
    <c- k>return</c-> <c- n>mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>make_dynamic_extent</c-><c- o>&lt;</c-><c- n>Pack</c-><c- o>></c-><c- p>()...</c-><c- o>></c-><c- p>(</c-><c- n>data</c-><c- p>,</c-> <c- n>extents</c-><c- p>);</c->
  <c- p>}</c->
<c- p>};</c->
</pre>
   <p>With <code class="highlight"><c- n>dextents</c-></code>, this becomes a lot simpler:</p>
<pre class="highlight"><c- k>template</c-> <c- o>&lt;</c-><c- k>typename</c-> <c- nc>T</c-><c- p>,</c-> <c- b>size_t</c-> <c- n>Rank</c-><c- o>></c->
<c- k>struct</c-> <c- nc>tensor</c-> <c- p>{</c->
  <c- n>T</c-><c- o>*</c-> <c- n>data</c-><c- p>;</c->
  <c- n>array</c-><c- o>&lt;</c-><c- b>size_t</c-><c- p>,</c-> <c- n>Rank</c-><c- o>></c-> <c- n>extents</c-><c- p>;</c->

  <c- k>auto</c-> <c- n>get_mdspan</c-><c- p>()</c-> <c- p>{</c->
    <c- k>return</c-> <c- n>mdspan</c-><c- p>(</c-><c- n>data</c-><c- p>,</c-> <c- n>dextents</c-><c- o>&lt;</c-><c- n>Rank</c-><c- o>></c-><c- p>(</c-><c- n>extents</c-><c- p>));</c->
  <c- p>}</c->
<c- p>};</c->
</pre>
   <h2 class="heading settled" data-level="4" id="convenience-alias"><span class="secno">4. </span><span class="content">Remove <code class="highlight"><c- n>mdspan</c-></code> Convenience Alias</span><a class="self-link" href="#convenience-alias"></a></h2>
   <p><code class="highlight"><c- n>dextents</c-></code> will have to be used with the unfortunately named <code class="highlight"><c- n>basic_mdspan</c-></code>.
I considered proposing something along the lines of <code class="highlight"><c- n>dynamic_mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>Rank</c-><c- o>></c-></code>.
However, this would potentially lead to confusion, as a <code class="highlight"><c- b>size_t</c-></code> non-type template
  parameter in <code class="highlight"><c- n>mdspan</c-></code> would mean "static extent of this size" while  a <code class="highlight"><c- b>size_t</c-></code> non-type
  template parameter in <code class="highlight"><c- n>dynamic_mdspan</c-></code> would mean "number of extents".</p>
   <table>
    <tbody>
     <tr>
      <th>Syntax 
      <th>Semantics 
     <tr>
      <td><code class="highlight"><c- n>span</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>N</c-><c- o>></c-></code> 
      <td><code class="highlight"><c- n>span</c-></code> with a static size of<code class="highlight"><c- n>N</c-></code>. 
     <tr>
      <td><code class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>N</c-><c- o>></c-></code> 
      <td><code class="highlight"><c- n>mdspan</c-></code> with a single static extent of size <code class="highlight"><c- n>N</c-></code>. 
     <tr>
      <td><code class="highlight"><c- n>dynamic_mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>N</c-><c- o>></c-></code> <b>(not proposed)</b> 
      <td><code class="highlight"><c- n>mdspan</c-></code> with <code class="highlight"><c- n>N</c-></code> dynamic extents. 
   </table>
   <p>Instead, I think we should:</p>
   <ul>
    <li data-md>
     <p>Delete the <code class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>Extents</c-><c- p>...</c-><c- o>></c-></code> alias.</p>
    <li data-md>
     <p>Rename <code class="highlight"><c- n>basic_mdspan</c-></code> to <code class="highlight"><c- n>mdspan</c-></code>.</p>
   </ul>
   <p>The purpose of the <code class="highlight"><c- n>mdspan</c-></code> alias was to provide a simple and easy to use
  interface for those with less complex and advanced use cases.
When the <code class="highlight"><c- n>mdspan</c-></code>/<code class="highlight"><c- n>basic_mdspan</c-></code> dichotomy was introduced when the proposal was
  first under consideration, before the existence of Class Template Argument
  Deduction and the proposed <code class="highlight"><c- n>dextents</c-></code>.
With the combination of these two forces, I believe that a separate <code class="highlight"><c- n>mdspan</c-></code> alias and <code class="highlight"><c- n>basic_mdspan</c-></code> class are unnecessary to achieve a simple and easy
  to use interface.</p>
   <table>
    <tbody>
     <tr>
      <th>Before 
      <td><code class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- o>></c-> <c- n>m</c-><c- p>(</c-><c- n>data</c-><c- p>,</c-> <c- mi>16</c-><c- p>,</c-> <c- mi>64</c-><c- p>,</c-> <c- mi>64</c-><c- p>);</c-></code> 
     <tr>
      <th>After 
      <td><code class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- o>></c-> <c- n>m</c-><c- p>(</c-><c- n>data</c-><c- p>,</c-> <c- mi>16</c-><c- p>,</c-> <c- mi>64</c-><c- p>,</c-> <c- mi>64</c-><c- p>);</c-></code> 
     <tr style="border: none !important">
      <td colspan="2" style="border: none !important; height: 10px">
     <tr>
      <th>Before 
      <td><code class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>dynamic_extent</c-><c- p>,</c-> <c- n>dynamic_extent</c-><c- p>,</c-> <c- n>dynamic_extent</c-><c- o>></c-> <c- n>f</c-><c- p>();</c-></code> 
     <tr>
      <th>After 
      <td><code class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>dextents</c-><c- o>&lt;</c-><c- mi>3</c-><c- o>>></c-> <c- n>f</c-><c- p>();</c-></code> 
     <tr style="border: none !important">
      <td colspan="2" style="border: none !important; height: 10px">
     <tr>
      <th>Before 
      <td><code class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- mi>3</c-><c- p>,</c-> <c- mi>3</c-><c- o>></c-> <c- n>m</c-><c- p>;</c-></code> 
     <tr>
      <th>After 
      <td><code class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>extents</c-><c- o>&lt;</c-><c- mi>3</c-><c- p>,</c-> <c- mi>3</c-><c- o>>></c-> <c- n>m</c-><c- p>;</c-></code> 
     <tr style="border: none !important">
      <td colspan="2" style="border: none !important; height: 10px">
     <tr>
      <th>Before 
      <td><code class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- mi>3</c-><c- p>,</c-> <c- mi>3</c-><c- o>></c-> <c- n>f</c-><c- p>();</c-></code> 
     <tr>
      <th>After 
      <td><code class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>extents</c-><c- o>&lt;</c-><c- mi>3</c-><c- p>,</c-> <c- mi>3</c-><c- o>>></c-> <c- n>f</c-><c- p>();</c-></code> 
     <tr style="border: none !important">
      <td colspan="2" style="border: none !important; height: 10px">
     <tr>
      <th>Before 
      <td><code class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- mi>16</c-><c- p>,</c-> <c- n>dynamic_extent</c-><c- p>,</c-> <c- mi>64</c-><c- o>></c-> <c- n>m</c-><c- p>;</c-></code> 
     <tr>
      <th>After 
      <td><code class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>extents</c-><c- o>&lt;</c-><c- mi>16</c-><c- p>,</c-> <c- n>dynamic_extent</c-><c- p>,</c-> <c- mi>64</c-><c- o>>></c-> <c- n>m</c-><c- p>;</c-></code> 
     <tr style="border: none !important">
      <td colspan="2" style="border: none !important; height: 10px">
     <tr>
      <th>Before 
      <td><code class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- mi>16</c-><c- p>,</c-> <c- n>dynamic_extent</c-><c- p>,</c-> <c- mi>64</c-><c- o>></c-> <c- n>f</c-><c- p>();</c-></code> 
     <tr>
      <th>After 
      <td><code class="highlight"><c- n>mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>extents</c-><c- o>&lt;</c-><c- mi>16</c-><c- p>,</c-> <c- n>dynamic_extent</c-><c- p>,</c-> <c- mi>64</c-><c- o>>></c-> <c- n>f</c-><c- p>();</c-></code> 
   </table>
   <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>
   <p>The following changes are relative to the <code class="highlight"><c- n>mdspan</c-></code> proposal (<a data-link-type="biblio" href="#biblio-p0009r12" title="MDSPAN">[P0009R12]</a>).</p>
   <p>The � character is used to denote a placeholder number which shall be selected by the editor.</p>
   <p>Modify the header synopsis for <code class="highlight"><c- o>&lt;</c-><c- n>mdspan</c-><c- o>></c-></code> in [<strong>mdspan.syn</strong>] as follows:</p>
   <blockquote>
     <b>22.7.� Header <code class="highlight"><c- o>&lt;</c-><c- n>mdspan</c-><c- o>></c-></code> synopsis <span style="float: right;">[mdspan.syn]</span></b> 
<pre class="highlight"><code><c- k>namespace</c-> <c- nn>std</c-> <c- p>{</c->
  <c- c1>// [mdspan.extents], class template extents</c->
  <c- k>template</c-><size_t... extents>
    <c- k>class</c-> <c- nc>extents</c-><c- p>;</c->

<div class="ins">  <c- k>template</c-><c- o>&lt;</c-><c- b>size_t</c-> <c- n>Rank</c-><c- o>></c->
    <c- k>using</c-> <c- n>dextents</c-> <c- o>=</c-> <c- k>decltype</c-><c- p>([]</c-> <c- o>&lt;</c-><c- b>size_t</c-><c- p>...</c-> <c- n>Pack</c-><c- o>></c-> <c- p>(</c-><c- n>index_sequence</c-><c- o>&lt;</c-><c- n>Pack</c-><c- p>...</c-><c- o>></c-><c- p>)</c-> <c- k>constexpr</c-> <c- p>{</c->
                       <c- k>return</c-> <c- n>extents</c-><c- o>&lt;</c-><c- p>[]</c-> <c- p>(</c-><c- k>auto</c-><c- p>)</c-> <c- k>constexpr</c->
                                      <c- p>{</c-> <c- k>return</c-> <c- n>dynamic_extent</c-><c- p>;</c-> <c- p>}</c->
                                      <c- p>(</c-><c- n>integral_constant</c-><c- o>&lt;</c-><c- b>size_t</c-><c- p>,</c-> <c- n>Pack</c-><c- o>></c-><c- p>{})...</c-><c- o>></c-><c- p>{};</c->
                     <c- p>}(</c-><c- n>make_index_sequence</c-><c- o>&lt;</c-><c- n>Rank</c-><c- o>></c-><c- p>{}));</c-></div>
  <c- c1>// [mdspan.layout], Layout mapping policies</c->
  <c- k>class</c-> <c- nc>layout_left</c-><c- p>;</c->
  <c- k>class</c-> <c- nc>layout_right</c-><c- p>;</c->
  <c- k>class</c-> <c- nc>layout_stride</c-><c- p>;</c->

  <c- c1>// [mdspan.accessor.basic]</c->
  <c- k>template</c-><c- o>&lt;</c-><c- k>class</c-> <c- nc>ElementType</c-><c- o>></c->
    <c- k>class</c-> <c- nc>default_accessor</c-><c- p>;</c->

  <c- c1>// [mdspan.basic], class template mdspan</c->
  <c- k>template</c-><c- o>&lt;</c-><c- k>class</c-> <c- nc>ElementType</c-><c- p>,</c-> <c- k>class</c-> <c- nc>Extents</c-><c- p>,</c-> <c- k>class</c-> <c- nc>LayoutPolicy</c-> <c- o>=</c-> <c- n>layout_right</c-><c- p>,</c->
           <c- k>class</c-> <c- nc>AccessorPolicy</c-> <c- o>=</c-> <c- n>default_accessor</c-><c- o>&lt;</c-><c- n>ElementType</c-><c- o>>></c->
    <c- k>class</c-> <c- nc>basic_mdspan</c-><c- p>;</c->

<div class="ins">  <c- k>template</c-> <c- o>&lt;</c-><c- k>class</c-> <c- nc>ElementType</c-><c- p>,</c-> <c- k>class</c-><c- p>...</c-> <c- n>Integrals</c-><c- o>></c->
  <c- k>explicit</c-> <c- n>basic_mdspan</c-><c- p>(</c-><c- n>ElementType</c-><c- o>*</c-><c- p>,</c-> <c- n>Integrals</c-><c- p>...)</c->
    <c- o>-></c-> <c- n>basic_mdspan</c-><c- o>&lt;</c-><c- n>ElementType</c-><c- p>,</c-> <c- n>dextents</c-><c- o>&lt;</c-><c- k>sizeof</c-><c- p>...(</c-><c- n>Integrals</c-><c- p>)</c-><c- o>></c-></div>
<div class="del">  <c- k>template</c-><c- o>&lt;</c-><c- k>class</c-> <c- nc>T</c-><c- p>,</c-> <c- b>size_t</c-><c- p>...</c-> <c- n>Extents</c-><c- o>></c->
    <c- k>using</c-> <c- n>mdspan</c-> <c- o>=</c-> <c- n>basic_mdspan</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>extents</c-><c- o>&lt;</c-><c- n>Extents</c-><c- p>...</c-><c- o>>></c-><c- p>;</c-></div>
  <c- c1>// [mdspan.submdspan]</c->
  <c- k>template</c-><c- o>&lt;</c-><c- k>class</c-> <c- nc>ElementType</c-><c- p>,</c-> <c- k>class</c-> <c- nc>Extents</c-><c- p>,</c-> <c- k>class</c-> <c- nc>LayoutPolicy</c-><c- p>,</c->
           <c- k>class</c-> <c- nc>AccessorPolicy</c-><c- p>,</c-> <c- k>class</c-><c- p>...</c-> <c- n>SliceSpecifiers</c-><c- o>></c->
    <c- k>constexpr</c-> <c- n>basic_mdspan</c-><c- o>&lt;</c-><i><c- n>see</c-> <c- n>below</c-></i><c- o>></c->
    <c- n>submdspan</c-><c- p>(</c-><c- k>const</c-> <c- n>basic_mdspan</c-><c- o>&lt;</c-><c- n>ElementType</c-><c- p>,</c-> <c- n>Extents</c-><c- p>,</c-> <c- n>LayoutPolicy</c-><c- p>,</c-> <c- n>AccessorPolicy</c-><c- o>>&amp;</c-> <c- n>m</c-><c- p>,</c->
              <c- n>SliceSpecifiers</c-><c- p>...</c-> <c- n>specs</c-><c- p>)</c-> <c- k>noexcept</c-><c- p>;</c->

  <c- c1>// tag supporting submdspan</c->
  <c- k>struct</c-> <c- nc>full_extent_t</c-> <c- p>{</c-> <c- k>explicit</c-> <c- n>full_extent_t</c-><c- p>()</c-> <c- o>=</c-> <c- k>default</c-><c- p>;</c-> <c- p>};</c->
  <c- kr>inline</c-> <c- k>constexpr</c-> <c- n>full_extent_t</c-> <c- n>full_extent</c-> <c- o>=</c-> <c- n>full_extent_t</c-><c- p>{};</c->
<c- p>}</c->
</size_t...></code></pre>
   </blockquote>
   <p>Replace all occurences of <code class="highlight"><c- n>basic_mdspan</c-></code> with <code class="highlight"><c- n>mdspan</c-></code>.</p>
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    var toggle = document.createElement('a');
      /* This should probably be a button, but appearance isn't standards-track.*/
    toggle.id = 'toc-toggle';
    toggle.class = 'toc-toggle';
    toggle.href = '#toc';
    toggle.innerHTML = collapseSidebarText;

    sidebarMedia.addListener(autoToggle);
    var toggler = function(e) {
      e.preventDefault();
      sidebarMedia.removeListener(autoToggle); // persist explicit off states
      toggleSidebar();
      return false;
    }
    toggle.addEventListener('click', toggler, false);


    /* Get <nav id=toc-nav>, or make it if we don't have one. */
    var tocNav = document.getElementById('toc-nav');
    if (!tocNav) {
      tocNav = document.createElement('p');
      tocNav.id = 'toc-nav';
      /* Prepend for better keyboard navigation */
      document.body.insertBefore(tocNav, document.body.firstChild);
    }
    /* While we're at it, make sure we have a Jump to Toc link. */
    var tocJump = document.getElementById('toc-jump');
    if (!tocJump) {
      tocJump = document.createElement('a');
      tocJump.id = 'toc-jump';
      tocJump.href = '#toc';
      tocJump.innerHTML = tocJumpText;
      tocNav.appendChild(tocJump);
    }

    tocNav.appendChild(toggle);
  }

  var toc = document.getElementById('toc');
  if (toc) {
    createSidebarToggle();
    toggleSidebar(sidebarMedia.matches);

    /* If the sidebar has been manually opened and is currently overlaying the text
       (window too small for the MQ to add the margin to body),
       then auto-close the sidebar once you click on something in there. */
    toc.addEventListener('click', function(e) {
      if(e.target.tagName.toLowerCase() == "a" && document.body.classList.contains('toc-sidebar') && !sidebarMedia.matches) {
        toggleSidebar(false);
      }
    }, false);
  }
  else {
    console.warn("Can't find Table of Contents. Please use <nav id='toc'> around the ToC.");
  }

  /* Wrap tables in case they overflow */
  var tables = document.querySelectorAll(':not(.overlarge) > table.data, :not(.overlarge) > table.index');
  var numTables = tables.length;
  for (var i = 0; i < numTables; i++) {
    var table = tables[i];
    var wrapper = document.createElement('div');
    wrapper.className = 'overlarge';
    table.parentNode.insertBefore(wrapper, table);
    wrapper.appendChild(table);
  }

})();
</script>
  <h2 class="no-num no-ref heading settled" id="references"><span class="content">References</span><a class="self-link" href="#references"></a></h2>
  <h3 class="no-num no-ref heading settled" id="informative"><span class="content">Informative References</span><a class="self-link" href="#informative"></a></h3>
  <dl>
   <dt id="biblio-p0009r12">[P0009R12]
   <dd>Christian Trott, D.S. Hollman, Damien Lebrun-Grandie, Mark Hoemmen, Daniel Sunderland, H. Carter Edwards, Bryce Adelstein Lelbach, Mauro Bianco, Ben Sander, Athanasios Iliopoulos, John Michopoulos, Nevin Liber. <a href="https://wg21.link/p0009r12"><cite>MDSPAN</cite></a>. 21 May 2021. URL: <a href="https://wg21.link/p0009r12">https://wg21.link/p0009r12</a>
  </dl>