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  <title>P3474R0: std::arguments</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>
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    del { background: #fcc; color: #000; text-decoration: line-through; }
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    blockquote c-[si] { color: inherit; } /* Literal.String.Interpol */
    blockquote c-[sx] { color: inherit; } /* Literal.String.Other */
    blockquote c-[sr] { color: inherit; } /* Literal.String.Regex */
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    blockquote c-[vc] { color: inherit; } /* Name.Variable.Class */
    blockquote c-[vg] { color: inherit; } /* Name.Variable.Global */
    blockquote c-[vi] { color: inherit; } /* Name.Variable.Instance */
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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">P3474R0<br><code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code></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="2024-10-15">2024-10-15</time></span></h2>
   <div data-fill-with="spec-metadata">
    <dl>
     <dt>This version:
     <dd><a class="u-url" href="https://isocpp.org/files/papers/P3474R0.html">https://isocpp.org/files/papers/P3474R0.html</a>
     <dt class="editor">Author:
     <dd class="editor p-author h-card vcard"><span class="p-name fn">Jeremy Rifkin</span>
     <dt>Audience:
     <dd>SG17, SG18
     <dt>Project:
     <dd>ISO/IEC 14882 Programming Languages — C++, ISO/IEC JTC1/SC22/WG21
     <dt>Source:
     <dd><a href="https://github.com/jeremy-rifkin/proposals/blob/main/cpp/arguments.bs">https://github.com/jeremy-rifkin/proposals/blob/main/cpp/arguments.bs</a>
    </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 an encoding-friendly and modern interface for accessing command line arguments throughout a program.</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="#credits"><span class="secno">1</span> <span class="content">Credits</span></a>
    <li><a href="#introduction"><span class="secno">2</span> <span class="content">Introduction</span></a>
    <li><a href="#previous-straw-polls-and-discussion"><span class="secno">3</span> <span class="content">Previous Straw Polls and Discussion</span></a>
    <li><a href="#implementability"><span class="secno">4</span> <span class="content">Implementability</span></a>
    <li>
     <a href="#proposed-design"><span class="secno">5</span> <span class="content">Proposed Design</span></a>
     <ol class="toc">
      <li><a href="#design-considerations"><span class="secno">5.1</span> <span class="content">Design Considerations</span></a>
      <li><a href="#future-interface-expansion"><span class="secno">5.2</span> <span class="content">Future Interface Expansion</span></a>
      <li><a href="#bikeshedding"><span class="secno">5.3</span> <span class="content">Bikeshedding</span></a>
     </ol>
    <li><a href="#reference-implementation"><span class="secno">6</span> <span class="content">Reference Implementation</span></a>
    <li><a href="#proposed-wording"><span class="secno">7</span> <span class="content">Proposed Wording</span></a>
    <li>
     <a href="#references"><span class="secno"></span> <span class="content">References</span></a>
     <ol class="toc">
      <li><a href="#normative"><span class="secno"></span> <span class="content">Normative References</span></a>
      <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="credits"><span class="secno">1. </span><span class="content">Credits</span><a class="self-link" href="#credits"></a></h2>
   <p><code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> was initially proposed by Izzy Muerte in <a data-link-type="biblio" href="#biblio-p1275" title="Desert Sessions: Improving hostile environment interactions">[P1275]</a>. Corentin Jabot and Aaron Ballman also proposed
an interface for accessing command line arguments outside <code class="highlight"><c- n>main</c-></code> to WG14 in <a data-link-type="biblio" href="#biblio-n2948" title="Accessing the command line arguments outside of main()">[N2948]</a>. This paper borrows wording,
design elements, and good ideas from both.</p>
   <h2 class="heading settled" data-level="2" id="introduction"><span class="secno">2. </span><span class="content">Introduction</span><a class="self-link" href="#introduction"></a></h2>
   <p>This paper aims to solve three problems: Encoding and portability problems with command line arguments, an interface for
accessing arguments outside of main, and a modern interface for accessing arguments. It does so by introducing a <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> class that provides a modern and encoding-friendly interface for arguments.</p>
   <p><strong>Encoding:</strong> The only standard means for accessing access command-line arguments in C++ is via <code class="highlight"><c- b>int</c-> <c- n>main</c-><c- p>(</c-><c- b>int</c-> <c- n>argc</c-><c- p>,</c-> <c- b>char</c-><c- o>**</c-> <c- n>argv</c-><c- p>)</c-></code>. This is a staple of C and C++, however, it’s not well-suited for portable applications because the
encoding of <code class="highlight"><c- n>argv</c-></code> varies system to system <a data-link-type="biblio" href="#biblio-what-is-the-encoding-of-argv" title="What is the encoding of argv?">[[What is the encoding of argv?]]</a>.
On Windows, the native encoding is UTF-16 and it’s recommended to use <code class="highlight"><c- n>wmain</c-></code> instead of <code class="highlight"><c- n>main</c-></code> for portable code. In
order to facilitate <code class="highlight"><c- n>argv</c-></code>, UTF-16 arguments must be converted using legacy Windows code pages. The preferred ways to
handle command line arguments on Windows are platform-specific functions, <code class="highlight"><c- n>WinMain</c-></code>, or <code class="highlight"><c- n>wmain</c-></code>. Even on Unix-based
systems the encoding of <code class="highlight"><c- b>char</c-><c- o>**</c-> <c- n>argv</c-></code> is not always clear. Tackling this problem more or less necessitates an interface
for accessing command line arguments independent of <code class="highlight"><c- n>main</c-></code> as adding a new signature to <code class="highlight"><c- n>main</c-></code> has been rejected by the
committee.</p>
   <p><strong>Access outside main:</strong> It may be desirable to access command line arguments outside of <code class="highlight"><c- n>main</c-></code> and even to do so before <code class="highlight"><c- n>main</c-></code>. Some examples could include logging diagnostic information in a crash handler and some designs for a command
line argument parser. Currently, command line arguments are only available inside of <code class="highlight"><c- n>main</c-></code> which requires a programmer
to manually pass arguments throughout the program or create their own global storage for arguments. This can add clutter
and introduce unnecessary complexity, especially if argument handling doesn’t happen "close" to <code class="highlight"><c- n>main</c-></code>. There is
precedent from other languages for global access, notably languages such as Python, Go, Rust, Swift, Ruby, C#, Haskell,
Ada, and many others provide an interface for accessing arguments from anywhere in a program. Additionally, many C++
frameworks make arguments available outside <code class="highlight"><c- n>main</c-></code>, such as QT with <code class="highlight"><c- n>QCoreApplication</c-><c- o>::</c-><c- n>arguments</c-></code>.</p>
   <p><strong>Modernity:</strong> Passing arrays via a pointer and length argument is a very antiquated pattern rendered obsolete by modern
solutions such as <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>span</c-></code>. <code class="highlight"><c- n>main</c-></code> is the one case where separate pointer and length arguments are still a
requirement if command line arguments are desired. A modern signature for <code class="highlight"><c- n>main</c-></code> along the lines of <code class="highlight"><c- b>int</c-> <c- n>main</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>span</c-><c- o>&lt;</c-><c- b>char</c-><c- o>*></c-> <c- n>argv</c-><c- p>)</c-></code>, <code class="highlight"><c- b>int</c-> <c- n>main</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>span</c-><c- o>&lt;</c-><c- n>std</c-><c- o>::</c-><c- n>string_view</c-><c- o>></c-> <c- n>argv</c-><c- p>)</c-></code>, or <code class="highlight"><c- b>int</c-> <c- n>main</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>argument_list</c-> <c- n>argv</c-><c- p>)</c-></code> was previously rejected by the committee due to concerns surrounding complexity, overhead, and encoding issues <a data-link-type="biblio" href="#biblio-p0781" title="A Modern C++ Signature for main">[P0781]</a>. On top of new functionality and increased portability, a facility such as <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> provides a modern
C++ solution for accessing arguments. An important benefit to this interface is teachability: Currently command line
arguments require introduction to pointers relatively early on in education as well as subjection to footguns and
confusion about the difference between C strings and C++ strings. This adds steepness to an already hazardously steep
learning curve.</p>
   <h2 class="heading settled" data-level="3" id="previous-straw-polls-and-discussion"><span class="secno">3. </span><span class="content">Previous Straw Polls and Discussion</span><a class="self-link" href="#previous-straw-polls-and-discussion"></a></h2>
   <p>Early polling surrounding an alternative to <code class="highlight"><c- n>argc</c-></code>/<code class="highlight"><c- n>argv</c-></code> and a means of accessing arguments outside of <code class="highlight"><c- n>main</c-></code> occurred
during discussion of <a data-link-type="biblio" href="#biblio-p0781" title="A Modern C++ Signature for main">[P0781]</a>:</p>
   <blockquote>
     POLL: A trivial library solution for iterating parameters? 
    <table>
     <thead>
      <tr>
       <th>SF
       <th>F
       <th>N
       <th>A
       <th>SA
     <tbody>
      <tr>
       <td>2
       <td>12
       <td>14
       <td>2
       <td>1
    </table>
   </blockquote>
   <blockquote>
     POLL: A non-<code class="highlight"><c- n>main</c-></code>-based way of fetching command line arguments? 
    <table>
     <thead>
      <tr>
       <th>SF
       <th>F
       <th>N
       <th>A
       <th>SA
     <tbody>
      <tr>
       <td>7
       <td>9
       <td>9
       <td>1
       <td>2
    </table>
   </blockquote>
   <p>Polls on <a data-link-type="biblio" href="#biblio-p1275" title="Desert Sessions: Improving hostile environment interactions">[P1275]</a> by LEWGI:</p>
   <blockquote>
    <p>POLL: We should promise more committee time to the <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> part.<br> Unanimous consent<br> Attendance: 11</p>
   </blockquote>
   <blockquote>
     POLL: <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> should be available before main 
    <table>
     <thead>
      <tr>
       <th>SF
       <th>F
       <th>N
       <th>A
       <th>SA
     <tbody>
      <tr>
       <td>6
       <td>0
       <td>3
       <td>1
       <td>0
    </table>
     Attendance: 11 
   </blockquote>
   <p>Polls on <a data-link-type="biblio" href="#biblio-p1275" title="Desert Sessions: Improving hostile environment interactions">[P1275]</a> by SG16:</p>
   <blockquote>
     POLL: <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>environments</c-></code> and <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> should follow the precedent set by <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>filesystem</c-><c- o>::</c-><c- n>path</c-></code>. 
    <table>
     <thead>
      <tr>
       <th>SF
       <th>F
       <th>N
       <th>A
       <th>SA
     <tbody>
      <tr>
       <td>4
       <td>6
       <td>1
       <td>0
       <td>2
    </table>
     Attendance: 14 
   </blockquote>
   <blockquote>
     POLL: <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>environment</c-></code> and <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> should return a bag-o-bytes and conversion is up to the user. 
    <table>
     <thead>
      <tr>
       <th>SF
       <th>F
       <th>N
       <th>A
       <th>SA
     <tbody>
      <tr>
       <td>3
       <td>4
       <td>2
       <td>1
       <td>2
    </table>
     Attendance: 14 
   </blockquote>
   <p>Key concerns discussed included mutability of arguments, overhead of initializing data structures before <code class="highlight"><c- n>main</c-></code>, and how to handle different encodings.</p>
   <h2 class="heading settled" data-level="4" id="implementability"><span class="secno">4. </span><span class="content">Implementability</span><a class="self-link" href="#implementability"></a></h2>
   <p>On Windows, command line arguments can be accessed by <code class="highlight"><c- n>GetCommandLineW</c-></code>. This function returns the command line as a
string which must then be tokenized. This is called by the Windows CRT during startup to populate <code class="highlight"><c- n>argv</c-></code> for main. The
Windows CRT also provide <code class="highlight"><c- n>__argv</c-></code> and <code class="highlight"><c- n>__wargv</c-></code> global variables but only populates one depending on <code class="highlight"><c- n>__UNICODE__</c-></code>.
Additionally, neither may be populated if the command line parsing is disabled via options tailored to applications
trying to minimize startup time.</p>
   <p>On MacOS, <code class="highlight"><c- n>_NSGetArgv</c-></code> and <code class="highlight"><c- n>_NSGetArgc</c-></code> can be used to access <code class="highlight"><c- n>argc</c-></code> and <code class="highlight"><c- n>argv</c-></code> outside of <code class="highlight"><c- n>main</c-></code>. These are both
trivial functions that don’t allocate.</p>
   <p>Implementation on other Unix-based systems is more challenging. There are four options:</p>
   <ol>
    <li data-md>
     <p>Modify libc to store <code class="highlight"><c- n>argv</c-></code> and <code class="highlight"><c- n>argc</c-></code> globally, e.g. <code class="highlight"><c- n>__argc</c-></code> and <code class="highlight"><c- n>__argv</c-></code>, similar to <code class="highlight"><c- n>__environ</c-></code>.
(<a href="https://github.com/cor3ntin/glibc/commit/d96b6f523b9526142f621df5ce9a1e71a592fca4">reference implementation for this from N2948</a>).</p>
    <li data-md>
     <p>Alternatively, store <code class="highlight"><c- n>argc</c-></code> and <code class="highlight"><c- n>argv</c-></code> from the program’s entry point. This would only require compiler support
instead of a libc change.</p>
    <li data-md>
     <p>Use <code class="highlight"><c- n>__dl_argv</c-></code> which exists in glibc. Unfortunately, absent a glibc change, looping through <code class="highlight"><c- n>__dl_argv</c-></code> would be
needed to determine <code class="highlight"><c- n>argc</c-></code> as <code class="highlight"><c- n>__dl_argc</c-></code> is hidden.</p>
    <li data-md>
     <p>Read from and tokenize <code class="highlight"><c- o>/</c-><c- n>proc</c-><c- o>/</c-><c- n>self</c-><c- o>/</c-><c- n>cmdline</c-></code>.</p>
    <li data-md>
     <p>Glibc passes <code class="highlight"><c- n>argc</c-></code> and <code class="highlight"><c- n>argv</c-></code> to entries in the <code class="highlight"><c- p>.</c-><c- n>init_array</c-></code>.</p>
   </ol>
   <h2 class="heading settled" data-level="5" id="proposed-design"><span class="secno">5. </span><span class="content">Proposed Design</span><a class="self-link" href="#proposed-design"></a></h2>
   <p>This paper introduces two classes, <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> and <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>argument</c-></code>, and a header, <code class="highlight"><c- o>&lt;</c-><c- n>arguments</c-><c- o>></c-></code>.</p>
   <p><code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> has the interface of a constant <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>span</c-></code> excluding the subview interface, modifiers, constructors, <code class="highlight"><c- n>size_bytes</c-></code>, and <code class="highlight"><c- n>data</c-></code>. Its default constructor initializes the object to represent the program’s command-line
arguments and may perform allocation.</p>
   <p><code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> has a <code class="highlight"><c- n>value_type</c-></code> of <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>argument</c-></code> which mirrors the design of <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>filesystem</c-><c- o>::</c-><c- n>path</c-></code> by providing
observers that can convert to desired encodings. SG16 indicated a desire to follow the precedent of <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>filesystem</c-><c- o>::</c-><c- n>path</c-></code>. Both paths and arguments can be encoded arbitrarily or even have no encoding; paths could be
any sequence of bytes and command line arguments can be too. <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>argument</c-></code> may be a view of a string or may own an
allocation.</p>
   <p>While it is not uncommon practice to modify the contents of <code class="highlight"><c- b>char</c-><c- o>**</c-> <c- n>argv</c-></code>, <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> is entirely read-only in
order to not introduce dangers surrounding global mutable state. Whether changes made to <code class="highlight"><c- n>argv</c-></code> in <code class="highlight"><c- n>main</c-></code> are reflected
in <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> is implementation-defined.</p>
   <h3 class="heading settled" data-level="5.1" id="design-considerations"><span class="secno">5.1. </span><span class="content">Design Considerations</span><a class="self-link" href="#design-considerations"></a></h3>
   <p>The main design considerations come down to allocation, when tokenization or other argument preprocessing happens, and
whether modifications to <code class="highlight"><c- n>argv</c-></code> in <code class="highlight"><c- n>main</c-></code> are reflected in <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code>.</p>
   <p><b>Reflecting <code class="highlight"><c- n>argv</c-></code> modifications from <code class="highlight"><c- n>main</c-></code>:</b> It is desirable for <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> to contain the same values
throughout the lifetime of a program and to not reflect changes to <code class="highlight"><c- n>argv</c-></code> in <code class="highlight"><c- n>main</c-></code>. Unfortunately, this would require
allocation and copying on some systems. On Unix-based systems all means to access <code class="highlight"><c- n>argv</c-></code> will
reflect changes to <code class="highlight"><c- n>argv</c-></code> in <code class="highlight"><c- n>main</c-></code>, including <code class="highlight"><c- o>/</c-><c- n>proc</c-><c- o>/</c-><c- n>self</c-><c- o>/</c-><c- n>cmdline</c-></code>. Discussion on <a data-link-type="biblio" href="#biblio-p1275" title="Desert Sessions: Improving hostile environment interactions">[P1275]</a> and <a data-link-type="biblio" href="#biblio-p0781" title="A Modern C++ Signature for main">[P0781]</a> made clear
that any overhead before <code class="highlight"><c- n>main</c-></code> in the case of programs that don’t use <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> is unacceptable. Unfortunately,
an initializer similar to <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>ios_base</c-><c- o>::</c-><c- n>Init</c-></code> isn’t an option due to shared libraries not necessarily being loaded
before <code class="highlight"><c- n>main</c-></code>. Additionally, with <code class="highlight"><c- k>import</c-> <c- n>std</c-><c- p>;</c-></code> this would translate to overhead before <code class="highlight"><c- n>main</c-></code> that is not pay for what
you use. Due to implementations challenges, this paper leaves behavior implementation-defined in the case of <code class="highlight"><c- n>argv</c-></code> being modified in <code class="highlight"><c- n>main</c-></code>.</p>
   <p><b>Saving <code class="highlight"><c- n>strlen</c-></code>:</b> On Unix-based systems, producing string views for arguments will involve a <code class="highlight"><c- n>strlen</c-></code>. It
may be desirable to save the result of this computation, however, the issue of modification mostly rules this out.
While the storage for the arguments from the system will always be there, the pointers in <code class="highlight"><c- n>argv</c-></code> could be modified and
detecting this would be sufficiently complicated, involve overhead, or in general may be impossible. Because of this,
every access of an argument string view will require a <code class="highlight"><c- n>strlen</c-></code> unless the implementation makes copies of <code class="highlight"><c- n>argv</c-></code> string
entries. It would likely be undesirable to make it undefined behavior to use <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> after modifications in <code class="highlight"><c- n>main</c-></code> so this paper leaves the possibility of a strlen cost open.</p>
   <p><b>Preprocessing:</b> On Windows <code class="highlight"><c- n>GetCommandLineW</c-></code> will return a string which needs to be split into individual
arguments. It may be desirable in some use-cases to only split this string lazily with an input-iterator interface for
arguments. This paper does not suggest any design constrained to input-iteration, though, as much use will want more
general access and iteration abilities and will require having tokenized all arguments anyway - whether by looping
through all the arguments or even just looking at the argument count.</p>
   <p><b>Backing storage for <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>argument</c-></code>s:</b> On Unix-based systems it would be simple for <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> to not
involve any allocation and simply provide iterators over <code class="highlight"><c- n>argv</c-></code> that dereference to ephemeral <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>argument</c-></code> objects.
Unfortunately, this would prevent the iterator from satisfying the <em>Cpp17RandomAccessIterator</em> requirements, container
requirements, and may be error prone in the case of trying to store a reference to a <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>argument</c-></code>. The proposed
requirements here will require backing storage.</p>
   <p><b>Global singleton, a function returning a reference, or construction:</b> <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> could be implemented as a
global singleton similar to <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>cout</c-></code>, a <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> function returning a reference to a singleton, or as an
object that the user constructs. While an object the user constructs potentially results in allocation at multiple
points in a program, as well as possibly seeing different values if <code class="highlight"><c- n>argv</c-></code> is modified in <code class="highlight"><c- n>main</c-></code>, it’s also desirable to
allow the <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> allocation to be cleaned up. As such, this paper proposes a <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> class which may
perform allocation and various preprocessing at construction.</p>
   <p><b>Globs and <code class="highlight"><c- n>argv</c-><c- p>[</c-><c- mi>0</c-><c- p>]</c-></code>:</b> On Unix-based systems glob expansion is done by the shell. On Windows it is neither done by
the shell or the Windows CRT. This paper proposes <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> should correspond directly to <code class="highlight"><c- n>argv</c-></code> in <code class="highlight"><c- n>main</c-></code> without any additional glob expansion. This paper also does not propose any special handling for the first entry of <code class="highlight"><c- n>argv</c-></code>.</p>
   <p><b>Comparison with other performance-oriented languages:</b> Rust’s <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>env</c-><c- o>::</c-><c- n>args</c-><c- p>()</c-></code> function creates an <code class="highlight"><c- n>Args</c-></code> object
which involves creating a vector of strings in the OS native encoding, copying from <code class="highlight"><c- n>argv</c-></code> on Unix-based systems and
tokenizing on Windows. Rust accesses <code class="highlight"><c- n>argv</c-></code> and <code class="highlight"><c- n>argc</c-></code> on most Unix-based systems by placing an initializer in the <code class="highlight"><c- p>.</c-><c- n>init_array</c-></code>. Rust doesn’t have to worry about modification of <code class="highlight"><c- n>argv</c-></code> in <code class="highlight"><c- n>main</c-></code>.</p>
   <p>Because the design of this library feature involves a lot of tradeoffs, it is the goal of this paper to offer as much
implementation flexibility as possible.</p>
   <h3 class="heading settled" data-level="5.2" id="future-interface-expansion"><span class="secno">5.2. </span><span class="content">Future Interface Expansion</span><a class="self-link" href="#future-interface-expansion"></a></h3>
   <p>Author’s note: While most large applications should probably use a library for argument parsing, it is my hope that in
the case of more ad-hoc argument parsing it would be possible to portably write a check such as <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-><c- p>.</c-><c- n>at</c-><c- p>(</c-><c- mi>1</c-><c- p>)</c-> <c- o>==</c-> <c- s>"--help"</c-></code> or <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-><c- p>.</c-><c- n>at</c-><c- p>(</c-><c- mi>1</c-><c- p>).</c-><c- n>native</c-><c- p>()</c-> <c- o>==</c-> <c- s>"--help"</c-></code>. Another helpful operation would be <code class="highlight"><c- p>.</c-><c- n>starts_with</c-><c- p>(</c-><c- s>"--"</c-><c- p>)</c-></code>. Unfortunately, encoding makes it challenging to do operations such as this portably.</p>
   <p>Because encoding will vary between systems and <code class="highlight"><c- n>native</c-><c- p>()</c-></code> is implementation-defined, currently the only way to do this
would involve the overhead of creating a string for a given encoding or an ugly macro to create a platform-dependent
string literal:</p>
<pre class="language-cpp highlight"><c- c1>// The overhead here is unfortunate but OK for 99% of uses</c->
<c- k>if</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>arguments</c-><c- p>.</c-><c- n>at</c-><c- p>(</c-><c- mi>1</c-><c- p>).</c-><c- n>string</c-><c- p>()</c-> <c- o>==</c-> <c- s>"--help"</c-><c- p>)</c-> <c- p>{</c->
  <c- c1>// ...</c->
<c- p>}</c->

<c- c1>// or:</c->

<c- cp>#ifdef _WIN32</c->
<c- cp>#define ARG(str) L##str</c->
<c- cp>#else</c->
<c- cp>#define ARG(str) str</c->
<c- cp>#endif</c->
<c- k>if</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>arguments</c-><c- p>.</c-><c- n>at</c-><c- p>(</c-><c- mi>1</c-><c- p>).</c-><c- n>native</c-><c- p>()</c-> <c- o>==</c-> <c- n>ARG</c-><c- p>(</c-><c- s>"--help"</c-><c- p>))</c-> <c- p>{</c->
  <c- c1>// ...</c->
<c- p>}</c->
</pre>
   <p>A UDL could also be considered, however, this is a more general problem that, in the author’s opinion, should be
addressed directly rather than through a bespoke solution. The problem of operations between strings of different
encodings would best be tackled in another paper.</p>
   <h3 class="heading settled" data-level="5.3" id="bikeshedding"><span class="secno">5.3. </span><span class="content">Bikeshedding</span><a class="self-link" href="#bikeshedding"></a></h3>
   <p>This paper uses the <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> naming from <a data-link-type="biblio" href="#biblio-p1275" title="Desert Sessions: Improving hostile environment interactions">[P1275]</a>, however, the name is subject to bikeshedding. One point
brought up on the mailing list was that <code class="highlight"><c- n>arguments</c-></code> is a very generic name and it might be desirable to reserve it for
future use. Some names that could be considered instead include:</p>
   <ul>
    <li data-md>
     <p><code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>program_arguments</c-></code></p>
    <li data-md>
     <p><code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>command_line</c-></code></p>
    <li data-md>
     <p><code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>command_line</c-><c- o>::</c-><c- n>arguments</c-></code></p>
    <li data-md>
     <p><code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>program_options</c-></code></p>
    <li data-md>
     <p><code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>argv</c-></code></p>
    <li data-md>
     <p><code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>process</c-><c- o>:</c-><c- n>arguments</c-></code></p>
   </ul>
   <p>Naming in other notable languages:</p>
   <ul>
    <li data-md>
     <p>Python: <code class="highlight"><c- n>sys</c-><c- p>.</c-><c- n>argv</c-></code></p>
    <li data-md>
     <p>Go: <code class="highlight"><c- n>os</c-><c- p>.</c-><c- n>Args</c-><c- p>()</c-></code></p>
    <li data-md>
     <p>Rust <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>env</c-><c- o>::</c-><c- n>args</c-><c- p>()</c-></code></p>
    <li data-md>
     <p>Swift: <code class="highlight"><c- n>CommandLine</c-><c- p>.</c-><c- n>arguments</c-></code></p>
    <li data-md>
     <p>Ruby: <code class="highlight"><c- n>ARGV</c-></code></p>
    <li data-md>
     <p>C#: <code class="highlight"><c- n>Environment</c-><c- p>.</c-><c- n>GetCommandLineArgs</c-><c- p>()</c-></code></p>
    <li data-md>
     <p>Haskell: <code class="highlight"><c- n>getArgs</c-><c- p>()</c-></code></p>
    <li data-md>
     <p>Ada: <code class="highlight"><c- n>Ada</c-><c- p>.</c-><c- n>Command_Line</c-><c- p>.</c-><c- n>Argument</c-></code></p>
   </ul>
   <p>In a very informal approval-voting-style poll on the Together C &amp; C++ Discord server (participants were asked to vote
for all they found appealing) members showed a strong preference for either <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>arguments</c-></code> or <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>argv</c-></code> with eight
and 17 votes respectively. Other options had no more than two votes. N.b.: The last option, <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>process</c-><c- o>::</c-><c- n>arguments</c-></code>,
came up after the poll was started and thus wasn’t captured in the poll.</p>
   <h2 class="heading settled" data-level="6" id="reference-implementation"><span class="secno">6. </span><span class="content">Reference Implementation</span><a class="self-link" href="#reference-implementation"></a></h2>
   <p>A reference implementation / proof of concept is at <a href="https://github.com/jeremy-rifkin/arguments">https://github.com/jeremy-rifkin/arguments</a>.</p>
   <h2 class="heading settled" data-level="7" id="proposed-wording"><span class="secno">7. </span><span class="content">Proposed Wording</span><a class="self-link" href="#proposed-wording"></a></h2>
   <p>Wording is relative to <a data-link-type="biblio" href="#biblio-n4950" title="Working Draft, Standard for Programming Language C++">[N4950]</a> and borrows extensively from existing wording.</p>
   <p>Insert into <a href="https://timsong-cpp.github.io/cppwp/n4950/headers">[headers]</a> table 24:</p>
   <blockquote>
    <ins><code class="highlight"><c- o>&lt;</c-><c- n>arguments</c-><c- o>></c-></code></ins>
   </blockquote>
   <p>Insert a new section [arguments]:</p>
   <div class="insall">
    <h3 class="no-num no-toc mono heading settled" id="header-arguments-synopsis-argumentssyn"><span class="content">Header <code class="highlight"><c- o>&lt;</c-><c- n>arguments</c-><c- o>></c-></code> synopsis [arguments.syn]</span><a class="self-link" href="#header-arguments-synopsis-argumentssyn"></a></h3>
<pre class="language-cpp highlight"><c- k>namespace</c-> <c- nn>std</c-> <c- p>{</c->
  <c- k>class</c-> <c- nc>argument</c-><c- p>;</c->
  <c- k>template</c-><c- o>&lt;</c-><c- k>class</c-> <c- nc>Allocator</c-> <c- o>=</c-> <c- n>allocator</c-><c- o>&lt;</c-><c- n>argument</c-><c- o>>></c-> <c- k>class</c-> <c- nc>arguments</c-><c- p>;</c->
<c- p>}</c->
</pre>
    <h3 class="no-num no-toc mono heading settled" id="class-arguments-argumentsview"><span class="content">Class <code class="highlight"><c- n>arguments</c-></code> [arguments.view]</span><a class="self-link" href="#class-arguments-argumentsview"></a></h3>
    <p>Class <code class="highlight"><c- n>arguments</c-></code> is a read-only container holding a continuous range of <code class="highlight"><c- n>argument</c-></code> objects corresponding to arguments passed to the program.</p>
    <p>All member functions of <code class="highlight"><c- n>arguments</c-></code> have constant time complexity except the constructor.</p>
<pre class="language-cpp highlight"><c- k>namespace</c-> <c- nn>std</c-> <c- p>{</c->
  <c- k>template</c-><c- o>&lt;</c-><c- k>class</c-> <c- nc>Allocator</c-> <c- o>=</c-> <c- n>allocator</c-><c- o>&lt;</c-><c- n>argument</c-><c- o>>></c->
  <c- k>class</c-> <c- nc>arguments</c-> <c- p>{</c->
  <c- k>public</c-><c- o>:</c->
    <c- k>using</c-> <c- n>value_type</c-> <c- o>=</c-> <c- k>const</c-> <c- n>argument</c-><c- p>;</c->
    <c- k>using</c-> <c- n>size_type</c-> <c- o>=</c-> <c- b>size_t</c-><c- p>;</c->
    <c- k>using</c-> <c- n>difference_type</c-> <c- o>=</c-> <c- b>ptrdiff_t</c-><c- p>;</c->
    <c- k>using</c-> <c- n>pointer</c-> <c- o>=</c-> <c- n>value_type</c-><c- o>*</c-><c- p>;</c->
    <c- k>using</c-> <c- n>const_pointer</c-> <c- o>=</c-> <c- n>value_type</c-><c- o>*</c-><c- p>;</c->
    <c- k>using</c-> <c- n>reference</c-> <c- o>=</c-> <c- n>value_type</c-><c- o>&amp;</c-><c- p>;</c->
    <c- k>using</c-> <c- n>const_reference</c-> <c- o>=</c-> <c- n>value_type</c-><c- o>&amp;</c-><c- p>;</c->
    <c- k>using</c-> <c- n>const_iterator</c-> <c- o>=</c-> <c- d>/* implementation-defined */</c-><c- p>;</c-> <c- c1>// see [arguments.view.iterators]</c->
    <c- k>using</c-> <c- n>iterator</c-> <c- o>=</c-> <c- n>const_iterator</c-><c- p>;</c->
    <c- k>using</c-> <c- n>const_reverse_iterator</c-> <c- o>=</c-> <c- n>std</c-><c- o>::</c-><c- n>reverse_iterator</c-><c- o>&lt;</c-><c- n>const_iterator</c-><c- o>></c-><c- p>;</c->
    <c- k>using</c-> <c- n>reverse_iterator</c-> <c- o>=</c-> <c- n>const_reverse_iterator</c-><c- p>;</c->

    <c- c1>// [arguments.view.cons], constructors</c->
    <c- n>arguments</c-><c- p>()</c-> <c- k>noexcept</c-><c- p>(</c-><c- k>noexcept</c-><c- p>(</c-><c- n>Allocator</c-><c- p>()))</c-> <c- o>:</c-> <c- n>arguments</c-><c- p>(</c-><c- n>Allocator</c-><c- p>())</c-> <c- p>{}</c->
    <c- k>explicit</c-> <c- n>arguments</c-><c- p>(</c-><c- k>const</c-> <c- n>Allocator</c-><c- o>&amp;</c-><c- p>);</c->

    <c- c1>// [arguments.view.access], access</c->
    <c- n>reference</c-> <c- k>operator</c-><c- p>[](</c-><c- n>size_type</c-> <c- n>index</c-><c- p>)</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c->
    <c- n>reference</c-> <c- nf>at</c-><c- p>(</c-><c- n>size_type</c-> <c- n>index</c-><c- p>)</c-> <c- k>const</c-><c- p>;</c->

    <c- c1>// [arguments.view.obs], observers</c->
    <c- n>size_type</c-> <c- nf>size</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c->
    <c- b>bool</c-> <c- nf>empty</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c->

    <c- c1>// [arguments.view.iterators], iterators</c->
    <c- n>const_iterator</c-> <c- nf>begin</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c->
    <c- n>const_iterator</c-> <c- nf>end</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c->

    <c- n>const_iterator</c-> <c- nf>cbegin</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c->
    <c- n>const_iterator</c-> <c- nf>cend</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c->

    <c- n>const_reverse_iterator</c-> <c- nf>rbegin</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c->
    <c- n>const_reverse_iterator</c-> <c- nf>rend</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c->

    <c- n>const_reverse_iterator</c-> <c- nf>crbegin</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c->
    <c- n>const_reverse_iterator</c-> <c- nf>crend</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c->
  <c- p>};</c->
<c- p>}</c->
</pre>
    <h4 class="no-num no-toc mono heading settled" id="constructors-argumentsviewcons"><span class="content">Constructors [arguments.view.cons]</span><a class="self-link" href="#constructors-argumentsviewcons"></a></h4>
    <p><code class="highlight"><c- k>explicit</c-> <c- n>arguments</c-><c- p>(</c-><c- k>const</c-> <c- n>Allocator</c-><c- o>&amp;</c-><c- p>)</c-> <c- k>noexcept</c-><c- p>;</c-></code></p>
    <p class="indent"><em>Effects</em>: Constructs an <code class="highlight"><c- n>arguments</c-></code> object with the program’s arguments using the specified allocator.</p>
    <p class="indent"><em>Throws</em>: May throw if <code class="highlight"><c- n>Allocator</c-><c- o>::</c-><c- n>allocate</c-></code> throws.</p>
    <h4 class="no-num no-toc mono heading settled" id="access-argumentsviewaccess"><span class="content">Access [arguments.view.access]</span><a class="self-link" href="#access-argumentsviewaccess"></a></h4>
    <p><code class="highlight"><c- n>value_type</c-> <c- k>operator</c-><c- p>[](</c-><c- n>size_type</c-> <c- n>index</c-><c- p>)</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c-></code></p>
    <p class="indent"><em>Preconditions</em>: <code class="highlight"><c- n>index</c-> <c- o>&lt;</c-> <c- n>size</c-><c- p>()</c-></code> is <code class="highlight">true</code>.</p>
    <p class="indent"><em>Returns</em>: The argument at index <code class="highlight"><c- n>index</c-></code> passed into the program from the environment. It is implementation-defined whether, in a <code class="highlight"><c- n>main</c-></code> function with signature <code class="highlight"><c- n>main</c-><c- p>(</c-><c- b>int</c-> <c- n>argc</c-><c- p>,</c-> <c- b>char</c-><c- o>**</c-> <c- n>argv</c-><c- p>)</c-></code>, any modifications to <code class="highlight"><c- n>argv</c-></code> are reflected by <code class="highlight"><c- n>arguments</c-><c- o>::</c-><c- k>operator</c-><c- p>[]</c-></code>.</p>
    <p class="indent"><em>Throws</em>: Nothing.</p>
    <p class="indent">[Note 1: <code class="highlight"><c- k>operator</c-><c- p>[](</c-><c- n>index</c-><c- p>)</c-></code> corresponds to <code class="highlight"><c- n>argv</c-><c- p>[</c-><c- n>index</c-><c- p>]</c-></code> in <code class="highlight"><c- n>main</c-><c- p>(</c-><c- b>int</c-> <c- n>argc</c-><c- p>,</c-> <c- b>char</c-><c- o>**</c-> <c- n>argv</c-><c- p>)</c-></code> — end note].</p>
    <p><code class="highlight"><c- n>value_type</c-> <c- nf>at</c-><c- p>(</c-><c- n>size_type</c-> <c- n>index</c-><c- p>)</c-> <c- k>const</c-><c- p>;</c-></code></p>
    <p class="indent"><em>Effects</em>: Equivalent to: <code class="highlight"><c- k>return</c-> <c- k>operator</c-><c- p>[](</c-><c- n>index</c-><c- p>);</c-></code> if <code class="highlight"><c- n>index</c-> <c- o>>=</c-> <c- n>size</c-><c- p>()</c-></code> is <code class="highlight">true</code>.</p>
    <p class="indent"><em>Throws</em>: <code class="highlight"><c- n>out_of_range</c-></code> if <code class="highlight"><c- n>index</c-> <c- o>>=</c-> <c- n>size</c-><c- p>()</c-></code> is <code class="highlight">true</code>.</p>
    <h4 class="no-num no-toc mono heading settled" id="observers-argumentsviewobs"><span class="content">Observers [arguments.view.obs]</span><a class="self-link" href="#observers-argumentsviewobs"></a></h4>
    <p><code class="highlight"><c- n>size_type</c-> <c- nf>size</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c-></code></p>
    <p class="indent"><em>Returns</em>: The number of program argument.</p>
    <p><code class="highlight"><c- n>size_type</c-> <c- nf>empty</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c-></code></p>
    <p class="indent"><em>Effects</em>: Equivalent to: <code class="highlight"><c- k>return</c-> <c- n>size</c-><c- p>()</c-> <c- o>==</c-> <c- mi>0</c-><c- p>;</c-></code></p>
    <h4 class="no-num no-toc mono heading settled" id="iterators-argumentsviewiterators"><span class="content">Iterators [arguments.view.iterators]</span><a class="self-link" href="#iterators-argumentsviewiterators"></a></h4>
    <p><code class="highlight"><c- k>using</c-> <c- n>const_iterator</c-> <c- o>=</c-> <c- d>/* implementation-defined */</c-><c- p>;</c-></code></p>
    <p class="indent"> The type models a <code class="highlight"><c- n>contiguous_iterator</c-></code> ([iterator.concept.contiguous]) and meets the <em>Cpp17RandomAccessIterator</em> requirements ([random.access.iterators]) whose value type is <code class="highlight"><c- n>value_type</c-></code> and whose reference type is <code class="highlight"><c- n>reference</c-></code>. </p>
    <p class="indent"> All requirements on container iterators ([container.reqmts]) apply to <code class="highlight"><c- n>arguments</c-><c- o>::</c-><c- n>iterator</c-></code> as well. </p>
    <p> <code class="highlight"><c- n>const_iterator</c-> <c- nf>begin</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c-></code><br> <code class="highlight"><c- n>const_iterator</c-> <c- nf>cbegin</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c-></code> </p>
    <p class="indent"> <em>Returns</em>: An iterator referring to the first program argument. If <code class="highlight"><c- n>empty</c-><c- p>()</c-></code> is <code class="highlight">true</code>, then it returns the same value
  as <code class="highlight"><c- n>end</c-><c- p>()</c-></code>. </p>
    <p> <code class="highlight"><c- n>const_iterator</c-> <c- nf>end</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c-></code><br> <code class="highlight"><c- n>const_iterator</c-> <c- nf>cend</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c-></code> </p>
    <p class="indent"> <em>Returns</em>: An iterator which is the past-the-end value. </p>
    <p> <code class="highlight"><c- n>const_iterator</c-> <c- nf>rbegin</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c-></code><br> <code class="highlight"><c- n>const_iterator</c-> <c- nf>crbegin</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c-></code> </p>
    <p class="indent"> <em>Effects</em>: Equivalent to: <code class="highlight"><c- k>return</c-> <c- n>reverse_iterator</c-><c- p>(</c-><c- n>end</c-><c- p>());</c-></code> </p>
    <p> <code class="highlight"><c- n>const_iterator</c-> <c- nf>rend</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c-></code><br> <code class="highlight"><c- n>const_iterator</c-> <c- nf>crend</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c-></code> </p>
    <p class="indent"> <em>Effects</em>: Equivalent to: <code class="highlight"><c- k>return</c-> <c- n>reverse_iterator</c-><c- p>(</c-><c- n>begin</c-><c- p>());</c-></code> </p>
    <h3 class="no-num no-toc mono heading settled" id="class-argument-argumentsargument"><span class="content">Class <code class="highlight"><c- n>argument</c-></code> [arguments.argument]</span><a class="self-link" href="#class-argument-argumentsargument"></a></h3>
    <p>An object of class <code class="highlight"><c- n>argument</c-></code> is a view of a character string argument passed to the program in an operating
system-dependent format.</p>
    <p>It is implementation-defined whether, in a <code class="highlight"><c- n>main</c-></code> function with signature <code class="highlight"><c- n>main</c-><c- p>(</c-><c- b>int</c-> <c- n>argc</c-><c- p>,</c-> <c- b>char</c-><c- o>**</c-> <c- n>argv</c-><c- p>)</c-></code>, any modifications to <code class="highlight"><c- n>argv</c-></code> are reflected by an <code class="highlight"><c- n>argument</c-></code>.</p>
<pre class="language-cpp highlight"><c- k>namespace</c-> <c- nn>std</c-> <c- p>{</c->
  <c- k>class</c-> <c- nc>argument</c-> <c- p>{</c->
  <c- k>public</c-><c- o>:</c->
    <c- k>using</c-> <c- n>value_type</c->  <c- o>=</c-> <c- d>/* see below */</c-><c- p>;</c->
    <c- k>using</c-> <c- n>string_type</c-> <c- o>=</c-> <c- n>basic_string</c-><c- o>&lt;</c-><c- n>value_type</c-><c- o>></c-><c- p>;</c->
    <c- k>using</c-> <c- n>string_view_type</c-> <c- o>=</c-> <c- n>basic_string_view</c-><c- o>&lt;</c-><c- n>value_type</c-><c- o>></c-><c- p>;</c->

    <c- c1>// [arguments.argument.native], native observers</c->
    <c- k>const</c-> <c- n>string_view_type</c-> <c- nf>native</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c->
    <c- k>const</c-> <c- n>string_type</c->      <c- nf>native_string</c-><c- p>()</c-> <c- k>const</c-><c- p>;</c->
    <c- k>const</c-> <c- n>value_type</c-><c- o>*</c->      <c- nf>c_str</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c->
    <c- k>explicit</c-> <c- k>operator</c-> <c- n>string_type</c-><c- p>()</c-> <c- k>const</c-><c- p>;</c->
    <c- k>explicit</c-> <c- k>operator</c-> <c- n>string_view_type</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c->

    <c- c1>// [arguments.argument.obs], converting observers</c->
    <c- k>template</c-><c- o>&lt;</c-><c- k>class</c-> <c- nc>EcharT</c-><c- p>,</c-> <c- k>class</c-> <c- nc>traits</c-> <c- o>=</c-> <c- n>char_traits</c-><c- o>&lt;</c-><c- n>EcharT</c-><c- o>></c-><c- p>,</c->
              <c- k>class</c-> <c- nc>Allocator</c-> <c- o>=</c-> <c- n>allocator</c-><c- o>&lt;</c-><c- n>EcharT</c-><c- o>>></c->
      <c- n>basic_string</c-><c- o>&lt;</c-><c- n>EcharT</c-><c- p>,</c-> <c- n>traits</c-><c- p>,</c-> <c- n>Allocator</c-><c- o>></c->
        <c- n>string</c-><c- p>(</c-><c- k>const</c-> <c- n>Allocator</c-><c- o>&amp;</c-> <c- n>a</c-> <c- o>=</c-> <c- n>Allocator</c-><c- p>())</c-> <c- k>const</c-><c- p>;</c->
    <c- n>std</c-><c- o>::</c-><c- n>string</c->    <c- nf>string</c-><c- p>()</c-> <c- k>const</c-><c- p>;</c->
    <c- n>std</c-><c- o>::</c-><c- n>wstring</c->   <c- nf>wstring</c-><c- p>()</c-> <c- k>const</c-><c- p>;</c->
    <c- n>std</c-><c- o>::</c-><c- n>u8string</c->  <c- nf>u8string</c-><c- p>()</c-> <c- k>const</c-><c- p>;</c->
    <c- n>std</c-><c- o>::</c-><c- n>u16string</c-> <c- nf>u16string</c-><c- p>()</c-> <c- k>const</c-><c- p>;</c->
    <c- n>std</c-><c- o>::</c-><c- n>u32string</c-> <c- nf>u32string</c-><c- p>()</c-> <c- k>const</c-><c- p>;</c->

    <c- c1>// [arguments.argument.compare], comparison</c->
    <c- k>friend</c-> <c- b>bool</c-> <c- k>operator</c-><c- o>==</c-><c- p>(</c-><c- k>const</c-> <c- n>argument</c-><c- o>&amp;</c-> <c- n>lhs</c-><c- p>,</c-> <c- k>const</c-> <c- n>argument</c-><c- o>&amp;</c-> <c- n>rhs</c-><c- p>)</c-> <c- k>noexcept</c-><c- p>;</c->
    <c- k>friend</c-> <c- n>strong_ordering</c-> <c- k>operator</c-><c- o>&lt;=></c-><c- p>(</c-><c- k>const</c-> <c- n>argument</c-><c- o>&amp;</c-> <c- n>lhs</c-><c- p>,</c-> <c- k>const</c-> <c- n>argument</c-><c- o>&amp;</c-> <c- n>rhs</c-><c- p>)</c-> <c- k>noexcept</c-><c- p>;</c->

    <c- c1>// [arguments.argument.ins], inserter</c->
    <c- k>template</c-><c- o>&lt;</c-><c- k>class</c-> <c- nc>charT</c-><c- p>,</c-> <c- k>class</c-> <c- nc>traits</c-><c- o>></c->
      <c- k>friend</c-> <c- n>basic_ostream</c-><c- o>&lt;</c-><c- n>charT</c-><c- p>,</c-> <c- n>traits</c-><c- o>>&amp;</c->
        <c- k>operator</c-><c- o>&lt;&lt;</c-><c- p>(</c-><c- n>basic_ostream</c-><c- o>&lt;</c-><c- n>charT</c-><c- p>,</c-> <c- n>traits</c-><c- o>>&amp;</c-> <c- n>os</c-><c- p>,</c-> <c- k>const</c-> <c- n>argument</c-><c- o>&amp;</c-> <c- n>a</c-><c- p>);</c->
  <c- p>};</c->

  <c- c1>// [arguments.argument.fmt], formatter</c->
  <c- k>template</c-><c- o>&lt;</c-><c- k>typename</c-> <c- nc>charT</c-><c- o>></c->
    <c- k>struct</c-> <c- nc>formatter</c-><c- o>&lt;</c-><c- n>argument</c-><c- p>,</c-> <c- n>charT</c-><c- o>></c->
      <c- o>:</c-> <c- n>formatter</c-><c- o>&lt;</c-><c- n>argument</c-><c- o>::</c-><c- n>string_view_type</c-><c- p>,</c-> <c- n>charT</c-><c- o>></c-> <c- p>{</c->
        <c- k>template</c-><c- o>&lt;</c-><c- k>class</c-> <c- nc>FormatContext</c-><c- o>></c->
          <c- k>typename</c-> <c- nc>FormatContext</c-><c- o>::</c-><c- n>iterator</c->
            <c- n>format</c-><c- p>(</c-><c- k>const</c-> <c- n>argument</c-><c- o>&amp;</c-> <c- n>argument</c-><c- p>,</c-> <c- n>FormatContext</c-><c- o>&amp;</c-> <c- n>ctx</c-><c- p>)</c-> <c- k>const</c-><c- p>;</c->
    <c- p>};</c->
<c- p>}</c->
</pre>
    <h4 class="no-num no-toc mono heading settled" id="conversion-argumentsargumentcvt"><span class="content">Conversion [arguments.argument.cvt]</span><a class="self-link" href="#conversion-argumentsargumentcvt"></a></h4>
    <p> The <em>native encoding</em> of an ordinary character string is the operating system dependent current encoding for arguments.
  The <em>native encoding</em> for wide character strings is the implementation-defined execution wide-character set encoding ([character.seq]). </p>
    <p> For member functions returning strings, value type and encoding conversion is performed if the value type of the
  argument or return value differs from <code class="highlight"><c- n>argument</c-><c- o>::</c-><c- n>value_type</c-></code>. For the return value, the method of conversion and the
  encoding to be converted to is determined by its value type: </p>
    <ul>
     <li> <code class="highlight"><c- b>char</c-></code>: The encoding is the native ordinary encoding. The method of conversion, if any, is operating system
    dependent. 
     <li> <code class="highlight"><c- b>wchar_t</c-></code>: The encoding is the native wide encoding. The method of conversion is unspecified. 
     <li> <code class="highlight"><c- b>char8_t</c-></code>: The encoding is UTF-8. The method of conversion is unspecified. 
     <li> <code class="highlight"><c- b>char16_t</c-></code>: The encoding is UTF-16. The method of conversion is unspecified. 
     <li> <code class="highlight"><c- b>char32_t</c-></code>: The encoding is UTF-32. The method of conversion is unspecified. 
    </ul>
    <p> If the encoding being converted to has no representation for source characters, the resulting converted characters, if
  any, are unspecified. </p>
    <h4 class="no-num no-toc mono heading settled" id="native-observers-argumentsargumentnative"><span class="content">Native Observers [arguments.argument.native]</span><a class="self-link" href="#native-observers-argumentsargumentnative"></a></h4>
    <p>The string returned by all native observers is in the native default argument encoding ([arguments.argument.cvt]).</p>
    <p><code class="highlight"><c- k>const</c-> <c- n>string_view_type</c-> <c- nf>native</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c-></code></p>
    <p class="indent"><em>Returns</em>: A <code class="highlight"><c- n>string_view_type</c-></code> representing the argument.</p>
    <p><code class="highlight"><c- k>const</c-> <c- n>string_type</c-> <c- nf>native_string</c-><c- p>()</c-> <c- k>const</c-><c- p>;</c-></code></p>
    <p class="indent"><em>Returns</em>: A <code class="highlight"><c- n>string_type</c-></code> representing the argument.</p>
    <p><code class="highlight"><c- k>const</c-> <c- n>value_type</c-><c- o>*</c-> <c- nf>c_str</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c-></code></p>
    <p class="indent"><em>Returns</em>: A pointer to a null-terminated array of <code class="highlight"><c- n>value_type</c-></code> representing the argument.</p>
    <p><code class="highlight"><c- k>operator</c-> <c- n>string_type</c-><c- p>()</c-> <c- k>const</c-><c- p>;</c-></code></p>
    <p class="indent"><em>Returns</em>: A <code class="highlight"><c- n>string_view_type</c-></code> representing the argument.</p>
    <p><code class="highlight"><c- k>operator</c-> <c- n>string_view_type</c-><c- p>()</c-> <c- k>const</c-> <c- k>noexcept</c-><c- p>;</c-></code></p>
    <p class="indent"><em>Returns</em>: A <code class="highlight"><c- n>string_type</c-></code> representing the argument.</p>
    <h4 class="no-num no-toc mono heading settled" id="converting-observers-argumentsargumentobs"><span class="content">Converting Observers [arguments.argument.obs]</span><a class="self-link" href="#converting-observers-argumentsargumentobs"></a></h4>
    <p> <code class="highlight"><c- k>template</c-><c- o>&lt;</c-><c- k>class</c-> <c- nc>EcharT</c-><c- p>,</c-> <c- k>class</c-> <c- nc>traits</c-> <c- o>=</c-> <c- n>char_traits</c-><c- o>&lt;</c-><c- n>EcharT</c-><c- o>></c-><c- p>,</c-></code><br> <code class="highlight">          </code><code class="highlight"><c- k>class</c-> <c- nc>Allocator</c-> <c- o>=</c-> <c- n>allocator</c-><c- o>&lt;</c-><c- n>EcharT</c-><c- o>>></c-></code><br> <code class="highlight">  </code><code class="highlight"><c- n>basic_string</c-><c- o>&lt;</c-><c- n>EcharT</c-><c- p>,</c-> <c- n>traits</c-><c- p>,</c-> <c- n>Allocator</c-><c- o>></c-></code><br> <code class="highlight">    </code><code class="highlight"><c- n>string</c-><c- p>(</c-><c- k>const</c-> <c- n>Allocator</c-><c- o>&amp;</c-> <c- n>a</c-> <c- o>=</c-> <c- n>Allocator</c-><c- p>())</c-> <c- k>const</c-><c- p>;</c-></code> </p>
    <p class="indent"><em>Returns</em>: A string representing the argument.</p>
    <p class="indent"><em>Remarks</em>: All memory allocation, including for the return value, shall be performed by a. Conversion, if any, is specified by [arguments.argument.cvt].</p>
    <p> <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>string</c-> <c- nf>string</c-><c- p>()</c-> <c- k>const</c-><c- p>;</c-></code><br> <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>wstring</c-> <c- nf>wstring</c-><c- p>()</c-> <c- k>const</c-><c- p>;</c-></code><br> <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>u8string</c-> <c- nf>u8string</c-><c- p>()</c-> <c- k>const</c-><c- p>;</c-></code><br> <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>u16string</c-> <c- nf>u16string</c-><c- p>()</c-> <c- k>const</c-><c- p>;</c-></code><br> <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>u32string</c-> <c- nf>u32string</c-><c- p>()</c-> <c- k>const</c-><c- p>;</c-></code> </p>
    <p class="indent"><em>Returns</em>: A string representing the argument.</p>
    <p class="indent"><em>Remarks</em>: Conversion, if any, is specified by [arguments.argument.cvt].</p>
    <h4 class="no-num no-toc mono heading settled" id="comparison-argumentsviewcompare"><span class="content">Comparison [arguments.view.compare]</span><a class="self-link" href="#comparison-argumentsviewcompare"></a></h4>
    <p><code class="highlight"><c- k>friend</c-> <c- b>bool</c-> <c- k>operator</c-><c- o>==</c-><c- p>(</c-><c- k>const</c-> <c- n>argument</c-><c- o>&amp;</c-> <c- n>lhs</c-><c- p>,</c-> <c- k>const</c-> <c- n>argument</c-><c- o>&amp;</c-> <c- n>rhs</c-><c- p>)</c-> <c- k>noexcept</c-><c- p>;</c-></code></p>
    <p class="indent"><em>Effects</em>: Equivalent to: <code class="highlight"><c- k>return</c-> <c- n>lhs</c-><c- p>.</c-><c- n>native</c-><c- p>()</c-> <c- o>==</c-> <c- n>rhs</c-><c- p>.</c-><c- n>native</c-><c- p>();</c-></code>.</p>
    <p><code class="highlight"><c- k>friend</c-> <c- n>strong_ordering</c-> <c- k>operator</c-><c- o>&lt;=></c-><c- p>(</c-><c- k>const</c-> <c- n>argument</c-><c- o>&amp;</c-> <c- n>lhs</c-><c- p>,</c-> <c- k>const</c-> <c- n>argument</c-><c- o>&amp;</c-> <c- n>rhs</c-><c- p>)</c-> <c- k>noexcept</c-><c- p>;</c-></code></p>
    <p class="indent"><em>Effects</em>: Equivalent to: <code class="highlight"><c- k>return</c-> <c- n>lhs</c-><c- p>.</c-><c- n>native</c-><c- p>()</c-> <c- o>&lt;=></c-> <c- n>rhs</c-><c- p>.</c-><c- n>native</c-><c- p>();</c-></code>.</p>
    <h4 class="no-num no-toc mono heading settled" id="inserter-argumentsargumentins"><span class="content">Inserter [arguments.argument.ins]</span><a class="self-link" href="#inserter-argumentsargumentins"></a></h4>
    <p> <code class="highlight"><c- k>template</c-><c- o>&lt;</c-><c- k>class</c-> <c- nc>charT</c-><c- p>,</c-> <c- k>class</c-> <c- nc>traits</c-><c- o>></c-></code><br> <code class="highlight">  </code><code class="highlight"><c- k>friend</c-> <c- n>basic_ostream</c-><c- o>&lt;</c-><c- n>charT</c-><c- p>,</c-> <c- n>traits</c-><c- o>>&amp;</c-></code><br> <code class="highlight">    </code><code class="highlight"><c- k>operator</c-><c- o>&lt;&lt;</c-><c- p>(</c-><c- n>basic_ostream</c-><c- o>&lt;</c-><c- n>charT</c-><c- p>,</c-> <c- n>traits</c-><c- o>>&amp;</c-> <c- n>os</c-><c- p>,</c-> <c- k>const</c-> <c- n>argument</c-><c- o>&amp;</c-> <c- n>a</c-><c- p>);</c-></code> </p>
    <p class="indent"><em>Effects</em>: Equivalent to: <code class="highlight"><c- k>return</c-> <c- n>os</c-> <c- o>&lt;&lt;</c-> <c- n>a</c-><c- p>.</c-><c- n>string</c-><c- o>&lt;</c-><c- n>charT</c-><c- p>,</c-> <c- n>traits</c-><c- o>></c-><c- p>();</c-></code>.</p>
    <h4 class="no-num no-toc mono heading settled" id="formatter-argumentsargumentfmt"><span class="content">Formatter [arguments.argument.fmt]</span><a class="self-link" href="#formatter-argumentsargumentfmt"></a></h4>
    <p> <code class="highlight"><c- k>template</c-><c- o>&lt;</c-><c- k>class</c-> <c- nc>FormatContext</c-><c- o>></c-></code><br> <code class="highlight">  </code><code class="highlight"><c- k>typename</c-> <c- nc>FormatContext</c-><c- o>::</c-><c- n>iterator</c-></code><br> <code class="highlight">    </code><code class="highlight"><c- n>format</c-><c- p>(</c-><c- k>const</c-> <c- n>argument</c-><c- o>&amp;</c-> <c- n>argument</c-><c- p>,</c-> <c- n>FormatContext</c-><c- o>&amp;</c-> <c- n>ctx</c-><c- p>)</c-> <c- k>const</c-><c- p>;</c-></code> </p>
    <p class="indent"><em>Effects</em>: Equivalent to: <code class="highlight"><c- k>return</c-> <c- n>std</c-><c- o>::</c-><c- n>formatter</c-><c- o>&lt;</c-><c- n>argument</c-><c- o>::</c-><c- n>string_view_type</c-><c- o>>::</c-><c- n>format</c-><c- p>(</c-><c- n>argument</c-><c- p>.</c-><c- n>string</c-><c- o>&lt;</c-><c- n>charT</c-><c- p>,</c-> <c- n>char_traits</c-><c- o>&lt;</c-><c- n>charT</c-><c- o>>></c-><c- p>(),</c-> <c- n>ctx</c-><c- p>);</c-></code>.</p>
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  <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="normative"><span class="content">Normative References</span><a class="self-link" href="#normative"></a></h3>
  <dl>
   <dt id="biblio-n4950">[N4950]
   <dd>Thomas Köppe. <a href="https://wg21.link/n4950"><cite>Working Draft, Standard for Programming Language C++</cite></a>. 10 May 2023. URL: <a href="https://wg21.link/n4950">https://wg21.link/n4950</a>
  </dl>
  <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-n2948">[N2948]
   <dd><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2948.pdf"><cite>Accessing the command line arguments outside of main()</cite></a>. URL: <a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2948.pdf">https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2948.pdf</a>
   <dt id="biblio-p0781">[P0781]
   <dd><a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0781r0.html"><cite>A Modern C++ Signature for main</cite></a>. URL: <a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0781r0.html">https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0781r0.html</a>
   <dt id="biblio-p1275">[P1275]
   <dd><a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1275r0.html"><cite>Desert Sessions: Improving hostile environment interactions</cite></a>. URL: <a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1275r0.html">https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1275r0.html</a>
   <dt id="biblio-what-is-the-encoding-of-argv">[What is the encoding of argv?]
   <dd><a href="https://stackoverflow.com/questions/5408730/what-is-the-encoding-of-argv"><cite>What is the encoding of argv?</cite></a>. URL: <a href="https://stackoverflow.com/questions/5408730/what-is-the-encoding-of-argv">https://stackoverflow.com/questions/5408730/what-is-the-encoding-of-argv</a>
  </dl>