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 <head>
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  <title>P1282R0: Ceci N’est Pas Une Pipe: Adding a workflow operator to C++</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
 *
 * 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)
 *   - .assertion  for assertions                    (div, p, span)
 *   - .advisement for loud normative statements     (div, p, strong)
 *   - .annoying-warning for spec obsoletion notices (div, aside, details)
 *
 * 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
 *
 * 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)
 *
 ******************************************************************************/

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

	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;

		/* Colors */
		color: black;
		background: white 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-width: .65rem .7rem .6rem;
		border-radius: .4rem;
		background: #1a5e9a;
		color: white;
		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;
		border-color: #c00;
	}

	/* 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: 2;
			bottom: 0; left: 0;
			margin: 0;
			min-width: 1.33em;
			border-top-right-radius: 2rem;
			box-shadow: 0 0 2px;
			font-size: 1.5em;
			color: black;
		}
		#toc-nav > a {
			display: block;
			white-space: nowrap;

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

			background: white;
			box-shadow: 0 0 2px;
			border: none;
			border-top-right-radius: 1.33em;
			background: white;
		}
		#toc-nav > #toc-jump {
			padding-bottom: 2em;
			margin-bottom: -1.9em;
		}

		#toc-nav > a:hover,
		#toc-nav > a:focus {
			background: #f8f8f8;
		}
		#toc-nav > a:not(:hover):not(:focus) {
			color: #707070;
		}

		/* 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-toggle-inline {
			vertical-align: 0.05em;
			font-size: 80%;
			color: gray;
			color: hsla(203,20%,40%,.7);
			border-style: none;
			background: transparent;
			position: relative;
		}
		#toc-toggle-inline:hover:not(:active),
		#toc-toggle-inline:focus:not(:active) {
			text-shadow: 1px 1px silver;
			top: -1px;
			left: -1px;
		}

		#toc-nav :active {
			color: #C00;
		}
	}

/** 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);
			background: inherit;
			background-color: #f7f8f9;
			z-index: 1;
			box-shadow: -.1em 0 .25em rgba(0,0,0,.1) 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);
		}
		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);
			background: inherit;
			background-color: #f7f8f9;
			z-index: 1;
			box-shadow: -.1em 0 .25em rgba(0,0,0,.1) 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);
		}

		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;
		background: transparent;
	}

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

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

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

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

	:not(.head) > hr {
		font-size: 1.5em;
		text-align: center;
		margin: 1em auto;
		height: auto;
		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;
	}

	/* Put nice boxes around each algorithm. */
	[data-algorithm]:not(.heading) {
	  padding: .5em;
	  border: thin solid #ddd; 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: medium;
	}
	dfn var {
		font-style: normal;
	}

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

	del { color: red;  text-decoration: line-through; }
	ins { color: #080; text-decoration: underline;    }

/** 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;
		page-break-inside: avoid;
		hyphens: none;
		text-transform: none;
	}
	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;
		text-decoration: none;
		border-bottom: 1px solid #707070;
		/* Need a bit of extending for it to look okay */
		padding: 0 1px 0;
		margin: 0 -1px 0;
	}
	a:visited {
		border-bottom-color: #BBB;
	}

	/* Use distinguishing colors when user is interacting with the link */
	a[href]:focus,
	a[href]:hover {
		background: #f8f8f8;
		background: rgba(75%, 75%, 75%, .25);
		border-bottom-width: 3px;
		margin-bottom: -2px;
	}
	a[href]:active {
		color: #C00;
		border-color: #C00;
	}

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

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

	img {
		border-style: none;
	}

	/* 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;
	}
	.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 {
		padding: .5em;
		border: .5em;
		border-left-style: solid;
		page-break-inside: avoid;
	}
	span.issue, span.note {
		padding: .1em .5em .15em;
		border-right-style: solid;
	}

	.issue,
	.note,
	.example,
	.advisement,
	.assertion,
	blockquote {
		margin: 1em auto;
	}
	.note  > p:first-child,
	.issue > p:first-child,
	blockquote > :first-child {
		margin-top: 0;
	}
	blockquote > :last-child {
		margin-bottom: 0;
	}

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

	blockquote {
		border-color: silver;
	}

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

	.issue {
		border-color: #E05252;
		background: #FBE9E9;
		counter-increment: issue;
		overflow: auto;
	}
	.issue::before, .issue > .marker {
		text-transform: uppercase;
		color: #AE1E1E;
		padding-right: 1em;
		text-transform: uppercase;
	}
	/* 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;
		background: #FCFAEE;
		counter-increment: example;
		overflow: auto;
		clear: both;
	}
	.example::before, .example > .marker {
		text-transform: uppercase;
		color: #827017;
		min-width: 7.5em;
		display: block;
	}
	/* 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;
		background: #E9FBE9;
		overflow: auto;
	}

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

	details.note > summary {
		display: block;
		color: hsl(120, 70%, 30%);
	}
	details.note[open] > summary {
		border-bottom: 1px silver solid;
	}

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

	.assertion {
		border-color: #AAA;
		background: #EEE;
	}

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

	.advisement {
		border-color: orange;
		border-style: none solid;
		background: #FFEECC;
	}
	strong.advisement {
		display: block;
		text-align: center;
	}
	.advisement > .marker {
		color: #B35F00;
	}

/** 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: #fdd;
		color: red;
		font-weight: bold;
		padding: .75em 1em;
		border: thick red;
		border-style: solid;
		border-radius: 1em;
	}
	.annoying-warning :last-child {
		margin-bottom: 0;
	}

@media not print {
	details.annoying-warning[open] {
		position: fixed;
		left: 1em;
		right: 1em;
		bottom: 1em;
		z-index: 1000;
	}
}

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

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

	.def {
		padding: .5em 1em;
		background: #DEF;
		margin: 1.2em 0;
		border-left: 0.5em solid #8CCBF2;
	}

/******************************************************************************/
/*                                    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;
	}

	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-top-style: solid;
	}

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

	table.data  thead,
	table.index thead,
	table.data  tbody,
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   <p data-fill-with="logo"></p>
   <h1 class="p-name no-ref" id="title">P1282R0<br>Ceci N’est Pas Une Pipe: Adding a workflow operator to C++</h1>
   <h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="content">Published Proposal, <time class="dt-updated" datetime="2018-09-27">2018-09-27</time></span></h2>
   <div data-fill-with="spec-metadata">
    <dl>
     <dt>This version:
     <dd><a class="u-url" href="https://wg21.link/p1282r0">https://wg21.link/p1282r0</a>
     <dt>Author:
     <dd>
      <dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:isabella.muerte@target.com">Isabella Muerte</a> (<span class="p-org org">Target</span>)
     <dt>Audience:
     <dd>EWG
     <dt>Toggle Diffs:
     <dd>
      <label for="hidedel" id="hidedel-label">Hide deleted text</label>
     <dt>Project:
     <dd>ISO/IEC JTC1/SC22/WG21 14882: Programming Language — C++
     <dt>Current Render:
     <dd><a href="https://api.csswg.org/bikeshed/?force=1&amp;url=https://git.io/fxsWc">P1282R0</a>
     <dt>Current Source:
     <dd><a href="https://git.io/fxsWC">slurps-mad-rips/papers/proposals/workflow-operator.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>Adding a workflow operator to C++ gives us the opportunity to solve

operator precedence for continuations on ranges, executors, monads,
coroutines, and anything else users might want.</p>
  </div>
  <nav data-fill-with="table-of-contents" id="toc">
   <h2 class="no-num no-toc no-ref" id="contents">Table of Contents</h2>
   <ol class="toc" role="directory">
    <li>
     <a href="#changelog"><span class="secno">1</span> <span class="content">Revision History</span></a>
     <ol class="toc">
      <li><a href="#r0"><span class="secno">1.1</span> <span class="content">Revision 0</span></a>
     </ol>
    <li><a href="#motivation"><span class="secno">2</span> <span class="content">Motivation</span></a>
    <li><a href="#design"><span class="secno">3</span> <span class="content">Design</span></a>
    <li>
     <a href="#faq"><span class="secno">4</span> <span class="content">FAQ</span></a>
     <ol class="toc">
      <li><a href="#faq-uses"><span class="secno">4.1</span> <span class="content">Does this have use beyond the stated examples so far?</span></a>
      <li><a href="#faq-fsharp"><span class="secno">4.2</span> <span class="content">Does this work like the <code class="highlight"><c- o>|></c-></code> operator from <code class="highlight"><c- n>F</c->#</code>?</span></a>
      <li><a href="#faq-more"><span class="secno">4.3</span> <span class="content">Are there any plans to add <code class="highlight"><c- o>&lt;|></c-></code> to this set of operators?</span></a>
      <li><a href="#faq-ufcs"><span class="secno">4.4</span> <span class="content">Does this solve the same problem as UFCS?</span></a>
      <li><a href="#faq-ufcs2"><span class="secno">4.5</span> <span class="content">Isn’t this just UFCS?</span></a>
      <li><a href="#faq-ufcs3"><span class="secno">4.6</span> <span class="content">I dunno, seems like UFCS to me</span></a>
      <li><a href="#faq-ufcs4"><span class="secno">4.7</span> <span class="content">OK, it’s just that it looks like its UFCS</span></a>
     </ol>
    <li>
     <a href="#examples"><span class="secno">5</span> <span class="content">Examples</span></a>
     <ol class="toc">
      <li><a href="#examples-range"><span class="secno">5.1</span> <span class="content">Ranges</span></a>
      <li><a href="#examples-monad"><span class="secno">5.2</span> <span class="content">Monads</span></a>
      <li>
       <a href="#examples-coroutine"><span class="secno">5.3</span> <span class="content">Coroutines And Executors</span></a>
       <ol class="toc">
        <li><a href="#examples-coroutine-2"><span class="secno">5.3.1</span> <span class="content">Case 2</span></a>
        <li><a href="#examples-coroutine-3"><span class="secno">5.3.2</span> <span class="content">Case 3</span></a>
        <li><a href="#examples-coroutine-4"><span class="secno">5.3.3</span> <span class="content">Case 4</span></a>
       </ol>
     </ol>
    <li><a href="#acknowledgements"><span class="secno">6</span> <span class="content">Acknowledgements</span></a>
    <li>
     <a href="#references"><span class="secno"></span> <span class="content">References</span></a>
     <ol class="toc">
      <li><a href="#informative"><span class="secno"></span> <span class="content">Informative References</span></a>
     </ol>
   </ol>
  </nav>
  <main>
   <h2 class="heading settled" data-level="1" id="changelog"><span class="secno">1. </span><span class="content">Revision History</span><a class="self-link" href="#changelog"></a></h2>
   <h3 class="heading settled" data-level="1.1" id="r0"><span class="secno">1.1. </span><span class="content">Revision 0</span><a class="self-link" href="#r0"></a></h3>
   <p>Initial release. 🎉</p>
   <h2 class="heading settled" data-level="2" id="motivation"><span class="secno">2. </span><span class="content">Motivation</span><a class="self-link" href="#motivation"></a></h2>
   <p>With the advent of Ranges, Executors, Coroutines, and monadic interfaces upon
us for C++20, we have a unique opportunity to create a uniform workflow
interface for expanding on each of the operations provided by the
aforementioned types.</p>
   <p>This paper proposes two operators, hereby dubbed the "workflow operators",
because they are not pipes, but for workflows. These workflow operators are
represented with the characters <code class="highlight"><c- o>|></c-></code> and <code class="highlight"><c- o>&lt;|</c-></code>. If you are currently seeing two
arrows on your screen, instead of a <code class="highlight"><c- o>|</c-></code> and <code class="highlight"><c- o>></c-></code>/<code class="highlight"><c- o>&lt;</c-></code> combo, you probably are
using a monospaced font with ligatures enabled. This paper does not recommend
unicode specific characters.</p>
   <h2 class="heading settled" data-level="3" id="design"><span class="secno">3. </span><span class="content">Design</span><a class="self-link" href="#design"></a></h2>
   <p>The plan is to define these operators' precedence such that they are above the
comma operator, but below the compound assignment operators. This should,
ideally, allow them to begin to be written in code with minimal interference
needed.</p>
   <p>Currently, ranges and executors plan on overloading the <code class="highlight"><c- o>|</c-></code> operator. This has
unidirectional meaning, but more importantly has precedence in between the
"bitwise xor" (<code class="highlight"><c- o>^</c-></code>) and "logcal and" (<code class="highlight"><c- n>and</c-></code>) operators. This can cause odd
and unexpected behavior. One could argue that overloading <code class="highlight"><c- o>>></c-></code> and <code class="highlight"><c- o>&lt;&lt;</c-></code> was a
mistake at the time. Perhaps we should take the opportunity to not repeat the
same type of mistake.</p>
   <p>Adding these operators has specific consequences, namely we don’t need a paper
everytime someone wants to add some kind of monadic operation to <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>optional</c-></code>, <code class="highlight"><c- n>std</c-><c- o>::</c-><c- n>expected</c-><c- o>/</c-><c- n>outcome</c-></code> or similar monadic types. In the past,
people such as Ben Deane and Simon Brand, have spoken that the best operator we
can get for proper binding is to use <code class="highlight"><c- o>>></c-></code>. However, its precedence means that
we actually have to use <code class="highlight"><c- o>>>=</c-></code>. Instead of overloading <em>that</em> operator, why
don’t we overload <code class="highlight"><c- o>|></c-></code> instead?</p>
   <p>We also would now have an operator that binds correctly when chaining
coroutines. Because <code class="highlight"><c- n>co_await</c-></code> (or whatever possible glyphs the committee
chooses) binds so tightly, we are currently unable to safely chain coroutines
in continuations without having to rely on member functions, or passing said
coroutines into another function to be executed later.</p>
   <p>While it is asking <em>a lot</em> to add more operators into C++20, the author
believes that this is an important requirement for composable and extensible
interfaces regarding the aforementioned executors, ranges, coroutines, monads,
and possibly even more interfaces.</p>
   <h2 class="heading settled" data-level="4" id="faq"><span class="secno">4. </span><span class="content">FAQ</span><a class="self-link" href="#faq"></a></h2>
   <h3 class="heading settled" data-level="4.1" id="faq-uses"><span class="secno">4.1. </span><span class="content">Does this have use beyond the stated examples so far?</span><a class="self-link" href="#faq-uses"></a></h3>
   <p>Several people on the cpplang slack channel have mentioned that it would be
useful for function composition and binding, as well as a possible "infix"
operator.</p>
   <h3 class="heading settled" data-level="4.2" id="faq-fsharp"><span class="secno">4.2. </span><span class="content">Does this work like the <code class="highlight"><c- o>|></c-></code> operator from <code class="highlight"><c- n>F</c->#</code>?</span><a class="self-link" href="#faq-fsharp"></a></h3>
   <p>The syntax is taken from F#, however the semantics differ greatly due to F#
being a garbage collected language, and an ML. C++ however is not either of
those and more things must be taken into account.</p>
   <h3 class="heading settled" data-level="4.3" id="faq-more"><span class="secno">4.3. </span><span class="content">Are there any plans to add <code class="highlight"><c- o>&lt;|></c-></code> to this set of operators?</span><a class="self-link" href="#faq-more"></a></h3>
   <p>At present there is no plan, however someone will probably find a use for it 🙂</p>
   <p>In all seriousness, there are possible uses for it <em>if</em> (and only if) C++ gets,
perhaps, channels as found in languages such as Rust or golang. That said, the
current <code class="highlight"><c- o>|></c-></code> and <code class="highlight"><c- o>&lt;|</c-></code> do not remove the need for, say, <code class="highlight"><c- n>when_all</c-></code>, and <code class="highlight"><c- n>when_any</c-></code> on futures or future-like types.</p>
   <h3 class="heading settled" data-level="4.4" id="faq-ufcs"><span class="secno">4.4. </span><span class="content">Does this solve the same problem as UFCS?</span><a class="self-link" href="#faq-ufcs"></a></h3>
   <p>No. UFCS gets us one step closer to concept maps and uniform interfaces. This
solves a different set of problems regarding operator precedence and extensible
interfaces.</p>
   <h3 class="heading settled" data-level="4.5" id="faq-ufcs2"><span class="secno">4.5. </span><span class="content">Isn’t this just UFCS?</span><a class="self-link" href="#faq-ufcs2"></a></h3>
   <p>No. UFCS has different semantics and requirements. This is just a regular old
operator users and library implementors can utilize to create extensible
interfaces with minimal interference into the way we write code.</p>
   <h3 class="heading settled" data-level="4.6" id="faq-ufcs3"><span class="secno">4.6. </span><span class="content">I dunno, seems like UFCS to me</span><a class="self-link" href="#faq-ufcs3"></a></h3>
   <p>It’s not UFCS. We have a new operator in C++20 (<code class="highlight"><c- o>&lt;=></c-></code>). We still don’t have
UFCS. This isn’t UFCS. Stop saying it’s UFCS. <em>It’s not UFCS</em>.</p>
   <h3 class="heading settled" data-level="4.7" id="faq-ufcs4"><span class="secno">4.7. </span><span class="content">OK, it’s just that it looks like its UFCS</span><a class="self-link" href="#faq-ufcs4"></a></h3>
   <p>No.</p>
   <h2 class="heading settled" data-level="5" id="examples"><span class="secno">5. </span><span class="content">Examples</span><a class="self-link" href="#examples"></a></h2>
   <p>The following examples show ranges, coroutines, and monad operations when
chaining operations via the workflow operators.</p>
   <h3 class="heading settled" data-level="5.1" id="examples-range"><span class="secno">5.1. </span><span class="content">Ranges</span><a class="self-link" href="#examples-range"></a></h3>
   <p>The following is taken (and modified) from the original ranges v3 draft</p>
<pre class="language-cpp highlight"><c- b>int</c-> <c- n>total</c-> <c- o>=</c-> <c- n>accumulate</c-> <c- p>{</c-> <c- mi>0</c-> <c- p>}</c-> <c- o>&lt;|</c-> <c- n>view</c-><c- o>::</c-><c- n>iota</c-><c- p>(</c-><c- mi>1</c-><c- p>)</c->
                             <c- o>|></c-> <c- n>view</c-><c- o>::</c-><c- n>transform</c-><c- p>([](</c-><c- b>int</c-> <c- n>x</c-><c- p>){</c-><c- k>return</c-> <c- n>x</c-><c- o>*</c-><c- n>x</c-><c- p>;})</c->
                             <c- o>|></c-> <c- n>view</c-><c- o>::</c-><c- n>take</c-><c- p>(</c-><c- mi>10</c-><c- p>);</c->
</pre>
   <p>In the above we create a range on the righthand side of <code class="highlight"><c- o>&lt;|</c-></code> and then pass this
in to our imaginary accumulate type that takes a range after being initialized
with its initial value. This could also technically be written as</p>
<pre class="language-cpp highlight"><c- b>int</c-> <c- n>total</c-> <c- o>=</c-> <c- n>view</c-><c- o>::</c-><c- n>iota</c-><c- p>(</c-><c- mi>1</c-><c- p>)</c->
            <c- o>|></c-> <c- n>view</c-><c- o>::</c-><c- n>transform</c-><c- p>([](</c-><c- b>int</c-> <c- n>x</c-><c- p>){</c-><c- k>return</c-> <c- n>x</c-><c- o>*</c-><c- n>x</c-><c- p>;})</c->
            <c- o>|></c-> <c- n>view</c-><c- o>::</c-><c- n>take</c-><c- p>(</c-><c- mi>10</c-><c- p>)</c->
            <c- o>|></c-> <c- n>accumulate</c-><c- p>(</c-><c- mi>0</c-><c- p>);</c->
</pre>
   <h3 class="heading settled" data-level="5.2" id="examples-monad"><span class="secno">5.2. </span><span class="content">Monads</span><a class="self-link" href="#examples-monad"></a></h3>
   <p>The following code was provided by Simon Brand via his CppCon 2018 talk on
monads. It has been slightly modified to cut down on length. It is a
demonstration of how we can extend existing interfaces without having to modify
existing syntax or creating a new DSL when interacting with standard (or soon
to be standard) types.</p>
   <p class="note" role="note"><span>Note:</span> This code is, minus the use of <code class="highlight"><c- k>operator</c-> <c- o>|></c-></code> valid C++17 code. With the
addition of Concepts, we could theoretically further constrain what operations
or interfaces can be flowed into a monadic type.</p>
<pre class="language-cpp highlight"><c- k>template</c-><c- o>&lt;</c-><c- k>typename</c-> <c- n>T</c-><c- p>,</c-> <c- k>typename</c-> <c- n>E</c-><c- p>,</c-> <c- k>typename</c-> <c- n>L</c-><c- o>></c->
<c- k>auto</c-> <c- n>map</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>expected</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>E</c-><c- o>></c-> <c- k>const</c-><c- o>&amp;</c-> <c- n>ex</c-><c- p>,</c-> <c- n>L</c-> <c- k>const</c-><c- o>&amp;</c-> <c- n>fun</c-><c- p>)</c->
  <c- o>-></c-> <c- n>expected</c-><c- o>&lt;</c-><c- k>decltype</c-><c- p>(</c-><c- n>fun</c-><c- p>(</c-><c- o>*</c-><c- n>ex</c-><c- p>)),</c-> <c- n>E</c-><c- o>></c-> <c- p>{</c->
    <c- k>if</c-> <c- p>(</c-><c- n>ex</c-><c- p>)</c-> <c- p>{</c-> <c- k>return</c-> <c- n>fun</c-><c- p>(</c-><c- o>*</c-><c- n>ex</c-><c- p>);</c-> <c- p>}</c->
    <c- k>return</c-> <c- n>std</c-><c- o>::</c-><c- n>make_unexpected</c-><c- p>(</c-><c- n>ex</c-><c- p>.</c-><c- n>error</c-><c- p>());</c->
<c- p>}</c->

<c- k>template</c-><c- o>&lt;</c-><c- k>typename</c-> <c- n>T</c-><c- p>,</c-> <c- k>typename</c-> <c- n>E</c-><c- p>,</c-> <c- k>typename</c-> <c- n>L</c-><c- o>></c->
<c- n>expected</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>E</c-><c- o>></c-> <c- n>join</c-> <c- p>(</c-><c- n>expected</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>E</c-><c- o>></c-> <c- k>const</c-><c- o>&amp;</c-> <c- n>ex</c-><c- p>,</c-> <c- n>L</c-> <c- k>const</c-><c- o>&amp;</c-> <c- n>fun</c-><c- p>)</c-> <c- p>{</c->
  <c- k>if</c-> <c- p>(</c-><c- n>ex</c-><c- p>)</c-> <c- p>{</c-> <c- k>return</c-> <c- o>*</c-><c- n>ex</c-><c- p>;</c-> <c- p>}</c->
  <c- k>return</c-> <c- n>std</c-><c- o>::</c-><c- n>make_unexpected</c-><c- p>(</c-><c- n>ex</c-><c- p>.</c-><c- n>error</c-><c- p>());</c->
<c- p>}</c->

<c- k>template</c-><c- o>&lt;</c-><c- k>typename</c-> <c- n>T</c-><c- p>,</c-> <c- k>typename</c-> <c- n>E</c-><c- p>,</c-> <c- k>typename</c-> <c- n>L</c-><c- o>></c->
<c- k>auto</c-> <c- n>and_then</c-><c- p>(</c-> <c- n>expected</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>E</c-><c- o>></c-> <c- k>const</c-><c- o>&amp;</c-> <c- n>ex</c-><c- p>,</c-> <c- n>L</c-> <c- k>const</c-><c- o>&amp;</c-> <c- n>fun</c-><c- p>)</c-> <c- p>{</c->
    <c- k>return</c-> <c- n>join</c-><c- p>(</c-><c- n>map</c-><c- p>(</c-><c- n>ex</c-><c- p>,</c-><c- n>fun</c-><c- p>));</c->
<c- p>}</c->

<c- k>namespace</c-> <c- n>infix</c-> <c- p>{</c->

<c- k>template</c-><c- o>&lt;</c-><c- k>typename</c-> <c- n>T</c-><c- o>></c->
<c- k>struct</c-> <c- n>map</c-> <c- p>{</c->
    <c- n>T</c-> <c- n>t</c-><c- p>;</c->
    <c- n>map</c-><c- p>(</c-><c- n>T</c-> <c- k>const</c-><c- o>&amp;</c-> <c- n>t</c-><c- p>)</c-> <c- o>:</c-> <c- n>t</c-><c- p>(</c-><c- n>t</c-><c- p>)</c-> <c- p>{}</c->
<c- p>};</c->

<c- k>template</c-><c- o>&lt;</c-><c- k>typename</c-> <c- n>T</c-><c- o>></c->
<c- k>struct</c-> <c- n>and_then</c-> <c- p>{</c->
    <c- n>T</c-> <c- n>t</c-><c- p>;</c->
    <c- n>and_then</c-><c- p>(</c-><c- n>T</c-> <c- k>const</c-><c- o>&amp;</c-> <c- n>t</c-><c- p>)</c-> <c- o>:</c-> <c- n>t</c-><c- p>(</c-><c- n>t</c-><c- p>)</c-> <c- p>{}</c->
<c- p>};</c->

<c- k>template</c-><c- o>&lt;</c-><c- k>typename</c-> <c- n>T</c-><c- p>,</c-> <c- k>typename</c-> <c- n>E</c-><c- p>,</c-> <c- k>typename</c-> <c- n>L</c-><c- o>></c->
<c- k>auto</c-> <c- k>operator</c-><c- o>|></c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>expected</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>E</c-><c- o>></c-> <c- k>const</c-><c- o>&amp;</c-> <c- n>ex</c-><c- p>,</c-> <c- n>map</c-> <c- k>const</c-><c- o>&amp;</c-> <c- n>fun</c-><c- p>)</c-> <c- p>{</c->
    <c- k>return</c-> <c- o>::</c-><c- n>map</c-><c- p>(</c-><c- n>ex</c-><c- p>,</c-> <c- n>fun</c-><c- p>.</c-><c- n>t</c-><c- p>);</c->
<c- p>}</c->

<c- k>template</c-><c- o>&lt;</c-><c- k>typename</c-> <c- n>T</c-><c- p>,</c-> <c- k>typename</c-> <c- n>E</c-><c- p>,</c-> <c- k>typename</c-> <c- n>L</c-><c- o>></c->
<c- k>auto</c-> <c- k>operator</c-><c- o>|></c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>expected</c-><c- o>&lt;</c-><c- n>T</c-><c- p>,</c-> <c- n>E</c-><c- o>></c-> <c- k>const</c-><c- o>&amp;</c-> <c- n>ex</c-><c- p>,</c-> <c- n>map</c-> <c- k>const</c-><c- o>&amp;</c-> <c- n>fun</c-><c- p>)</c-> <c- p>{</c->
    <c- k>return</c-> <c- o>::</c-><c- n>and_then</c-><c- p>(</c-><c- n>ex</c-><c- p>,</c-> <c- n>fun</c-><c- p>.</c-><c- n>t</c-><c- p>);</c->
<c- p>}</c->

<c- p>}</c-> <c- d>/* namespace infix */</c->

<c- n>std</c-><c- o>::</c-><c- n>expected</c-><c- o>&lt;</c-><c- b>int</c-><c- p>,</c-> <c- n>string</c-><c- o>></c-> <c- n>divide</c-> <c- p>(</c-><c- b>int</c-> <c- n>numerator</c-><c- p>,</c-> <c- b>int</c-> <c- n>denominator</c-><c- p>)</c-> <c- p>{</c->
  <c- k>if</c-> <c- p>(</c-><c- n>denominator</c-> <c- o>==</c-> <c- mi>0</c-><c- p>)</c-> <c- p>{</c-> <c- k>return</c-> <c- n>std</c-><c- o>::</c-><c- n>make_unexpected</c-><c- p>(</c-> <c- s>"divide by zero"</c-> <c- p>);</c-> <c- p>}</c->
  <c- k>return</c-> <c- n>numerator</c-> <c- o>/</c-> <c- n>denominator</c-><c- p>;</c->
<c- p>}</c->

<c- n>std</c-><c- o>::</c-><c- n>expected</c-><c- o>&lt;</c-><c- b>int</c-><c- p>,</c-> <c- n>std</c-><c- o>::</c-><c- n>string</c-><c- o>></c-> <c- n>to_int</c-><c- p>(</c-><c- n>std</c-><c- o>::</c-><c- n>string</c-> <c- k>const</c-><c- o>&amp;</c-> <c- n>s</c-><c- p>)</c-> <c- p>{</c->
  <c- k>if</c-> <c- p>(</c-><c- n>s</c-><c- p>.</c-><c- n>empty</c-><c- p>())</c-> <c- p>{</c-> <c- k>return</c-> <c- n>std</c-><c- o>::</c-><c- n>make_unexpected</c-><c- p>(</c-><c- s>"string was empty"</c-><c- n>s</c-><c- p>);</c-> <c- p>}</c->
  <c- b>int</c-> <c- n>i</c-><c- p>;</c->
  <c- k>auto</c-> <c- n>result</c-> <c- o>=</c-> <c- n>from_chars</c-><c- p>(</c-><c- o>&amp;</c-><c- n>s</c-><c- p>.</c-><c- n>front</c-><c- p>(),</c-> <c- o>&amp;</c-><c- n>s</c-><c- p>.</c-><c- n>back</c-><c- p>(),</c-> <c- n>i</c-><c- p>);</c->
  <c- k>if</c-> <c- p>(</c-><c- n>result</c-><c- p>.</c-><c- n>ec</c-> <c- n>or</c-> <c- n>result</c-><c- p>.</c-><c- n>ptr</c-> <c- o>!=</c-> <c- o>&amp;</c-><c- n>s</c-><c- p>.</c-><c- n>back</c-><c- p>())</c-> <c- p>{</c->
    <c- k>return</c-> <c- n>std</c-><c- o>::</c-><c- n>make_unexpected</c-><c- p>(</c-><c- s>"string did not contain an int"</c-><c- n>s</c-><c- p>);</c->
  <c- p>}</c->
  <c- k>return</c-> <c- n>i</c-><c- p>;</c->
<c- p>}</c->

<c- b>int</c-> <c- n>main</c-><c- p>()</c-> <c- p>{</c->
  <c- k>using</c-> <c- k>namespace</c-> <c- n>infix</c-><c- p>;</c->
  <c- k>auto</c-> <c- n>result</c-> <c- o>=</c-> 
    <c- n>to_int</c-><c- p>(</c-><c- s>"12"</c-><c- p>)</c->
    <c- o>|></c-> <c- n>and_then</c-><c- p>([]</c-> <c- p>(</c-><c- b>int</c-> <c- n>i</c-><c- p>)</c-> <c- p>{</c-> <c- k>return</c-> <c- n>divide</c-><c- p>(</c-><c- mi>42</c-><c- p>,</c-> <c- n>i</c-> <c- p>);</c-> <c- p>})</c->
    <c- o>|></c-> <c- n>map</c-><c- p>([]</c-> <c- p>(</c-><c- b>double</c-> <c- n>d</c-><c- p>)</c-> <c- p>{</c-> <c- k>return</c-> <c- n>d</c-> <c- o>*</c-> <c- mi>2</c-><c- p>;</c-> <c- p>});</c->
</pre>
   <h3 class="heading settled" data-level="5.3" id="examples-coroutine"><span class="secno">5.3. </span><span class="content">Coroutines And Executors</span><a class="self-link" href="#examples-coroutine"></a></h3>
   <p>The following code is modified regarding coroutines and its (possible)
interactions with executors found in <a data-link-type="biblio" href="#biblio-p1056r0">[p1056r0]</a>. While this code may not seem
very explanatory, the interaction between coroutines and executors is still not
well defined. However, unlike the need to implement <code class="highlight"><c- p>.</c-><c- n>via</c-></code> as a member function
and having to "await" any changes if newer and better interfaces are found,
users are free to implement their own interfaces on <code class="highlight"><c- n>task</c-><c- o>&lt;</c-><c- n>T</c-><c- o>></c-></code>, coroutine types,
executors, or a combination of them.</p>
   <p>Recall, however, that a coroutine <em>starts</em> suspended and it is up to the user
to decide how it is executed and where its continuation is placed.</p>
   <h4 class="heading settled" data-level="5.3.1" id="examples-coroutine-2"><span class="secno">5.3.1. </span><span class="content">Case 2</span><a class="self-link" href="#examples-coroutine-2"></a></h4>
<pre class="language-cpp highlight"><c- n>co_await</c-> <c- nf>f</c-><c- p>()</c-> <c- o>|></c-> <c- n>via</c-><c- p>(</c-><c- n>e</c-><c- p>);</c->
</pre>
   <h4 class="heading settled" data-level="5.3.2" id="examples-coroutine-3"><span class="secno">5.3.2. </span><span class="content">Case 3</span><a class="self-link" href="#examples-coroutine-3"></a></h4>
   <p>Starts by an executor <code class="highlight"><c- n>ex</c-></code>, resumes in the thread that triggered the completion
of <code class="highlight"><c- n>f</c-></code></p>
<pre class="language-cpp highlight"><c- n>co_await</c-> <c- nf>spawn</c-><c- p>(</c-><c- n>ex</c-><c- p>)</c-> <c- o>|></c-> <c- n>f</c-><c- p>;</c->
</pre>
   <h4 class="heading settled" data-level="5.3.3" id="examples-coroutine-4"><span class="secno">5.3.3. </span><span class="content">Case 4</span><a class="self-link" href="#examples-coroutine-4"></a></h4>
   <p>Starts on executor <code class="highlight"><c- n>ex1</c-></code>, resumes on executor <code class="highlight"><c- n>ex2</c-></code></p>
<pre class="language-cpp highlight"><c- n>co_await</c-> <c- n>spawn</c-><c- p>(</c-><c- n>ex1</c-><c- p>)</c-> <c- o>|></c-> <c- n>f</c-> <c- o>|></c-> <c- n>via</c-><c- p>(</c-><c- n>ex2</c-><c- p>)</c->
</pre>
   <h2 class="heading settled" data-level="6" id="acknowledgements"><span class="secno">6. </span><span class="content">Acknowledgements</span><a class="self-link" href="#acknowledgements"></a></h2>
   <p>Special thanks for Simon Brand for providing his source code. The encouragement
of Simon Brand, Phil Nash, David Hollman, and countless others (I’m so sorry,
there’s a LOT of you and I can’t remember all of you) to move forward with this
paper after I originally suggested it in passing to Louis Dionne at CppCon</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>
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  <dl>
   <dt id="biblio-p1056r0">[P1056R0]
   <dd>Lewis Baker, Gor Nishanov. <a href="https://wg21.link/p1056r0">Add coroutine task type</a>. 5 May 2018. URL: <a href="https://wg21.link/p1056r0">https://wg21.link/p1056r0</a>
  </dl>
