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html {
    --sans-serif-family: "Noto Sans", sans-serif;
    --serif-family: "Noto Serif", serif;
    --monospace-family: "Fira Code", monospace;

    --light-background-color: white;
    --light-deep-background-color: #fafafa;
    --light-text-color: black;
    --light-border-color: #aaa;
    --light-table-border-color: #777;
    --light-del-color: #be1621;
    --light-del-background-color: #fbe6e8;
    --light-ins-color: #17752d;
    --light-ins-background-color: #e4faea;
    --light-para-color: rgb(10, 73, 136);
    --light-a-color: rgb(10, 73, 136);
    --light-a-visited-color: rgb(44, 10, 136);
    --light-a-hover-color: rgb(15, 93, 170);
    --light-mark-color: black;
    --light-mark-background-color: #ffff85;
    --light-abstract-border-color: #707070;
    --light-abstract-background-color: #f0f0f0;
    --light-abstract-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23707070"><path d="M660-160h40v-160h-40v160Zm20-200q8 0 14-6t6-14q0-8-6-14t-14-6q-8 0-14 6t-6 14q0 8 6 14t14 6ZM200-800v640-640 200-200Zm80 400h147q11-23 25.5-43t32.5-37H280v80Zm0 160h123q-3-20-3-40t3-40H280v80ZM200-80q-33 0-56.5-23.5T120-160v-640q0-33 23.5-56.5T200-880h320l240 240v92q-19-6-39-9t-41-3v-40H480v-200H200v640h227q11 23 25.5 43T485-80H200Zm480-400q83 0 141.5 58.5T880-280q0 83-58.5 141.5T680-80q-83 0-141.5-58.5T480-280q0-83 58.5-141.5T680-480Z"/></svg>');
    --light-blockquote-border-color: #707070;
    --light-blockquote-background-color: #f0f0f0;
    --light-blockquote-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 0 24 24" width="24px" fill="%23707070"><path d="M0 0h24v24H0V0z" fill="none"/><path d="M7.17 17c.51 0 .98-.29 1.2-.74l1.42-2.84c.14-.28.21-.58.21-.89V8c0-.55-.45-1-1-1H5c-.55 0-1 .45-1 1v4c0 .55.45 1 1 1h2l-1.03 2.06c-.45.89.2 1.94 1.2 1.94zm10 0c.51 0 .98-.29 1.2-.74l1.42-2.84c.14-.28.21-.58.21-.89V8c0-.55-.45-1-1-1h-4c-.55 0-1 .45-1 1v4c0 .55.45 1 1 1h2l-1.03 2.06c-.45.89.2 1.94 1.2 1.94z"/></svg>');
    --light-bug-block-border-color: #9f7b5d;
    --light-bug-block-background-color: #f0e2d9;
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    --light-decision-block-border-color: #ab6fa2;
    --light-decision-block-background-color: #f4e6f4;
    --light-decision-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23ab6fa2"><path d="M160-120v-80h480v80H160Zm226-194L160-540l84-86 228 226-86 86Zm254-254L414-796l86-84 226 226-86 86Zm184 408L302-682l56-56 522 522-56 56Z"/></svg>');
    --light-del-block-border-color: #be1621;
    --light-del-block-background-color: #fbe6e8;
    --light-del-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23be1621"><path d="M280-120q-33 0-56.5-23.5T200-200v-520h-40v-80h200v-40h240v40h200v80h-40v520q0 33-23.5 56.5T680-120H280Zm400-600H280v520h400v-520ZM360-280h80v-360h-80v360Zm160 0h80v-360h-80v360ZM280-720v520-520Z"/></svg>');
    --light-details-border-color: #707070;
    --light-details-background-color: #f0f0f0;
    --light-details-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23707070"><path d="M440-280h80v-240h-80v240Zm40-320q17 0 28.5-11.5T520-640q0-17-11.5-28.5T480-680q-17 0-28.5 11.5T440-640q0 17 11.5 28.5T480-600Zm0 520q-83 0-156-31.5T197-197q-54-54-85.5-127T80-480q0-83 31.5-156T197-763q54-54 127-85.5T480-880q83 0 156 31.5T763-763q54 54 85.5 127T880-480q0 83-31.5 156T763-197q-54 54-127 85.5T480-80Zm0-80q134 0 227-93t93-227q0-134-93-227t-227-93q-134 0-227 93t-93 227q0 134 93 227t227 93Zm0-320Z"/></svg>');
    --light-diff-block-border-color: #707070;
    --light-diff-block-background-color: #f0f0f0;
    --light-diff-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23707070"><path d="M500-520h80v-80h80v-80h-80v-80h-80v80h-80v80h80v80Zm-80 160h240v-80H420v80ZM320-200q-33 0-56.5-23.5T240-280v-560q0-33 23.5-56.5T320-920h280l240 240v400q0 33-23.5 56.5T760-200H320Zm0-80h440v-360L560-840H320v560ZM160-40q-33 0-56.5-23.5T80-120v-560h80v560h440v80H160Zm160-240v-560 560Z"/></svg>');
    --light-example-block-border-color: #6f8aab;
    --light-example-block-background-color: #e6e9f4;
    --light-example-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%236f8aab"><path d="M300-80q-58 0-99-41t-41-99v-520q0-58 41-99t99-41h500v600q-25 0-42.5 17.5T740-220q0 25 17.5 42.5T800-160v80H300Zm-60-267q14-7 29-10t31-3h20v-440h-20q-25 0-42.5 17.5T240-740v393Zm160-13h320v-440H400v440Zm-160 13v-453 453Zm60 187h373q-6-14-9.5-28.5T660-220q0-16 3-31t10-29H300q-26 0-43 17.5T240-220q0 26 17 43t43 17Z"/></svg>');
    --light-important-block-border-color: #b05252;
    --light-important-block-background-color: #f4e6e6;
    --light-important-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23ab6f6f"><path d="M480-120q-33 0-56.5-23.5T400-200q0-33 23.5-56.5T480-280q33 0 56.5 23.5T560-200q0 33-23.5 56.5T480-120Zm-80-240v-480h160v480H400Z"/></svg>');
    --light-ins-block-border-color: #17752d;
    --light-ins-block-background-color: #e4faea;
    --light-ins-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%2317752d"><path d="M440-240h80v-120h120v-80H520v-120h-80v120H320v80h120v120ZM240-80q-33 0-56.5-23.5T160-160v-640q0-33 23.5-56.5T240-880h320l240 240v480q0 33-23.5 56.5T720-80H240Zm280-520v-200H240v640h480v-440H520ZM240-800v200-200 640-640Z"/></svg>');
    --light-note-block-border-color: #6fab6f;
    --light-note-block-background-color: #e6f4e9;
    --light-note-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%236fab6f"><path d="M440-280h80v-240h-80v240Zm40-320q17 0 28.5-11.5T520-640q0-17-11.5-28.5T480-680q-17 0-28.5 11.5T440-640q0 17 11.5 28.5T480-600Zm0 520q-83 0-156-31.5T197-197q-54-54-85.5-127T80-480q0-83 31.5-156T197-763q54-54 127-85.5T480-880q83 0 156 31.5T763-763q54 54 85.5 127T880-480q0 83-31.5 156T763-197q-54 54-127 85.5T480-80Zm0-80q134 0 227-93t93-227q0-134-93-227t-227-93q-134 0-227 93t-93 227q0 134 93 227t227 93Zm0-320Z"/></svg>');
    --light-tip-block-border-color: #b0a029;
    --light-tip-block-background-color: #f4f4e6;
    --light-tip-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23b0a029"><path d="M480-80q-33 0-56.5-23.5T400-160h160q0 33-23.5 56.5T480-80ZM320-200v-80h320v80H320Zm10-120q-69-41-109.5-110T180-580q0-125 87.5-212.5T480-880q125 0 212.5 87.5T780-580q0 81-40.5 150T630-320H330Zm24-80h252q45-32 69.5-79T700-580q0-92-64-156t-156-64q-92 0-156 64t-64 156q0 54 24.5 101t69.5 79Zm126 0Z"/></svg>');
    --light-todo-block-border-color: #6faba0;
    --light-todo-block-background-color: #e6f4f3;
    --light-todo-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%236faba0"><path d="M680-80q-83 0-141.5-58.5T480-280q0-83 58.5-141.5T680-480q83 0 141.5 58.5T880-280q0 83-58.5 141.5T680-80Zm67-105 28-28-75-75v-112h-40v128l87 87Zm-547 65q-33 0-56.5-23.5T120-200v-560q0-33 23.5-56.5T200-840h167q11-35 43-57.5t70-22.5q40 0 71.5 22.5T594-840h166q33 0 56.5 23.5T840-760v250q-18-13-38-22t-42-16v-212h-80v120H280v-120h-80v560h212q7 22 16 42t22 38H200Zm280-640q17 0 28.5-11.5T520-800q0-17-11.5-28.5T480-840q-17 0-28.5 11.5T440-800q0 17 11.5 28.5T480-760Z"/></svg>');
    --light-warning-block-border-color: #af8141;
    --light-warning-block-background-color: #f4eee6;
    --light-warning-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23af8141"><path d="M109-120q-11 0-20-5.5T75-140q-5-9-5.5-19.5T75-180l370-640q6-10 15.5-15t19.5-5q10 0 19.5 5t15.5 15l370 640q6 10 5.5 20.5T885-140q-5 9-14 14.5t-20 5.5H109Zm69-80h604L480-720 178-200Zm302-40q17 0 28.5-11.5T520-280q0-17-11.5-28.5T480-320q-17 0-28.5 11.5T440-280q0 17 11.5 28.5T480-240Zm0-120q17 0 28.5-11.5T520-400v-120q0-17-11.5-28.5T480-560q-17 0-28.5 11.5T440-520v120q0 17 11.5 28.5T480-360Zm0-100Z"/></svg>');
    --light-theme-icon: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="black"><path d="M480-360q50 0 85-35t35-85q0-50-35-85t-85-35q-50 0-85 35t-35 85q0 50 35 85t85 35Zm0 80q-83 0-141.5-58.5T280-480q0-83 58.5-141.5T480-680q83 0 141.5 58.5T680-480q0 83-58.5 141.5T480-280ZM200-440H40v-80h160v80Zm720 0H760v-80h160v80ZM440-760v-160h80v160h-80Zm0 720v-160h80v160h-80ZM256-650l-101-97 57-59 96 100-52 56Zm492 496-97-101 53-55 101 97-57 59Zm-98-550 97-101 59 57-100 96-56-52ZM154-212l101-97 55 53-97 101-59-57Zm326-268Z"/></svg>');

    --dark-background-color: #202020;
    --dark-deep-background-color: #1a1a1a;
    --dark-text-color: #f0f0f0;
    --dark-border-color: #505050;
    --dark-table-border-color: #777;
    --dark-del-background-color: #67060c;
    --dark-del-color: #ffdcd7;
    --dark-ins-background-color: #033a16;
    --dark-ins-color: #aff5b4;
    --dark-para-color: #5bc0ff;
    --dark-a-color: #5bc0ff;
    --dark-a-visited-color: #c6a8ff;
    --dark-a-hover-color: #afd7ff;
    --dark-mark-color: #ededa8;
    --dark-mark-background-color: #525230;
    --dark-abstract-border-color: #999999;
    --dark-abstract-background-color: #2c2c2c;
    --dark-abstract-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23999999"><path d="M660-160h40v-160h-40v160Zm20-200q8 0 14-6t6-14q0-8-6-14t-14-6q-8 0-14 6t-6 14q0 8 6 14t14 6ZM200-800v640-640 200-200Zm80 400h147q11-23 25.5-43t32.5-37H280v80Zm0 160h123q-3-20-3-40t3-40H280v80ZM200-80q-33 0-56.5-23.5T120-160v-640q0-33 23.5-56.5T200-880h320l240 240v92q-19-6-39-9t-41-3v-40H480v-200H200v640h227q11 23 25.5 43T485-80H200Zm480-400q83 0 141.5 58.5T880-280q0 83-58.5 141.5T680-80q-83 0-141.5-58.5T480-280q0-83 58.5-141.5T680-480Z"/></svg>');
    --dark-blockquote-border-color: #707070;
    --dark-blockquote-background-color: #2c2c2c;
    --dark-blockquote-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 0 24 24" width="24px" fill="%23707070"><path d="M0 0h24v24H0V0z" fill="none"/><path d="M7.17 17c.51 0 .98-.29 1.2-.74l1.42-2.84c.14-.28.21-.58.21-.89V8c0-.55-.45-1-1-1H5c-.55 0-1 .45-1 1v4c0 .55.45 1 1 1h2l-1.03 2.06c-.45.89.2 1.94 1.2 1.94zm10 0c.51 0 .98-.29 1.2-.74l1.42-2.84c.14-.28.21-.58.21-.89V8c0-.55-.45-1-1-1h-4c-.55 0-1 .45-1 1v4c0 .55.45 1 1 1h2l-1.03 2.06c-.45.89.2 1.94 1.2 1.94z"/></svg>');
    --dark-bug-block-border-color: #ab866f;
    --dark-bug-block-background-color: #373028;
    --dark-bug-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23ab866f"><path d="M480-120q-64 0-114.5-33T283-240l-95 54-40-69 103-60q-3-11-5-22.5t-4-22.5H120v-80h122q2-12 4-23.5t5-22.5l-103-60 40-69 94 55q8-14 18.5-27.5T322-612q-2-7-2-14v-14q0-24 7-46t19-41l-66-66 56-57 70 68q17-9 35.5-13.5T480-800q20 0 39 5t36 14l69-69 56 57-66 66q12 19 18.5 41t6.5 46v13.5q0 6.5-2 13.5 11 11 21.5 25t18.5 28l95-54 40 69-104 59q3 11 5.5 22.5T718-440h122v80H718q-2 12-4 23.5t-5 22.5l103 60-40 69-95-55q-32 54-82.5 87T480-120Zm-76-546q17-7 36.5-10.5T480-680q20 0 38.5 3t35.5 10q-8-23-28-38t-46-15q-26 0-47 15.5T404-666Zm76 466q73 0 116.5-61T640-400q0-70-40.5-135T480-600q-78 0-119 64.5T320-400q0 78 43.5 139T480-200Zm-40-80v-240h80v240h-80Z"/></svg>');
    --dark-details-border-color: #707070;
    --dark-details-background-color: #2c2c2c;
    --dark-details-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23707070"><path d="M440-280h80v-240h-80v240Zm40-320q17 0 28.5-11.5T520-640q0-17-11.5-28.5T480-680q-17 0-28.5 11.5T440-640q0 17 11.5 28.5T480-600Zm0 520q-83 0-156-31.5T197-197q-54-54-85.5-127T80-480q0-83 31.5-156T197-763q54-54 127-85.5T480-880q83 0 156 31.5T763-763q54 54 85.5 127T880-480q0 83-31.5 156T763-197q-54 54-127 85.5T480-80Zm0-80q134 0 227-93t93-227q0-134-93-227t-227-93q-134 0-227 93t-93 227q0 134 93 227t227 93Zm0-320Z"/></svg>');
    --dark-decision-block-border-color: #ab6fa2;
    --dark-decision-block-background-color: #30232d;
    --dark-decision-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23ab6fa2"><path d="M160-120v-80h480v80H160Zm226-194L160-540l84-86 228 226-86 86Zm254-254L414-796l86-84 226 226-86 86Zm184 408L302-682l56-56 522 522-56 56Z"/></svg>');
    --dark-del-block-border-color: #be5e64;
    --dark-del-block-background-color: #302323;
    --dark-del-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23be5e64"><path d="M280-120q-33 0-56.5-23.5T200-200v-520h-40v-80h200v-40h240v40h200v80h-40v520q0 33-23.5 56.5T680-120H280Zm400-600H280v520h400v-520ZM360-280h80v-360h-80v360Zm160 0h80v-360h-80v360ZM280-720v520-520Z"/></svg>');
    --dark-diff-block-border-color: #707070;
    --dark-diff-block-background-color: #2c2c2c;
    --dark-diff-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23707070"><path d="M500-520h80v-80h80v-80h-80v-80h-80v80h-80v80h80v80Zm-80 160h240v-80H420v80ZM320-200q-33 0-56.5-23.5T240-280v-560q0-33 23.5-56.5T320-920h280l240 240v400q0 33-23.5 56.5T760-200H320Zm0-80h440v-360L560-840H320v560ZM160-40q-33 0-56.5-23.5T80-120v-560h80v560h440v80H160Zm160-240v-560 560Z"/></svg>');
    --dark-example-block-border-color: #6f81ab;
    --dark-example-block-background-color: #232630;
    --dark-example-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%236f81ab"><path d="M300-80q-58 0-99-41t-41-99v-520q0-58 41-99t99-41h500v600q-25 0-42.5 17.5T740-220q0 25 17.5 42.5T800-160v80H300Zm-60-267q14-7 29-10t31-3h20v-440h-20q-25 0-42.5 17.5T240-740v393Zm160-13h320v-440H400v440Zm-160 13v-453 453Zm60 187h373q-6-14-9.5-28.5T660-220q0-16 3-31t10-29H300q-26 0-43 17.5T240-220q0 26 17 43t43 17Z"/></svg>');
    --dark-important-block-border-color: #b06262;
    --dark-important-block-background-color: #302323;
    --dark-important-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23b06262"><path d="M480-120q-33 0-56.5-23.5T400-200q0-33 23.5-56.5T480-280q33 0 56.5 23.5T560-200q0 33-23.5 56.5T480-120Zm-80-240v-480h160v480H400Z"/></svg>');
    --dark-ins-block-border-color: #5bab6d;
    --dark-ins-block-background-color: #233023;
    --dark-ins-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%235bab6d"><path d="M440-240h80v-120h120v-80H520v-120h-80v120H320v80h120v120ZM240-80q-33 0-56.5-23.5T160-160v-640q0-33 23.5-56.5T240-880h320l240 240v480q0 33-23.5 56.5T720-80H240Zm280-520v-200H240v640h480v-440H520ZM240-800v200-200 640-640Z"/></svg>');
    --dark-note-block-border-color: #6fab76;
    --dark-note-block-background-color: #233025;
    --dark-note-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%236fab76"><path d="M440-280h80v-240h-80v240Zm40-320q17 0 28.5-11.5T520-640q0-17-11.5-28.5T480-680q-17 0-28.5 11.5T440-640q0 17 11.5 28.5T480-600Zm0 520q-83 0-156-31.5T197-197q-54-54-85.5-127T80-480q0-83 31.5-156T197-763q54-54 127-85.5T480-880q83 0 156 31.5T763-763q54 54 85.5 127T880-480q0 83-31.5 156T763-197q-54 54-127 85.5T480-80Zm0-80q134 0 227-93t93-227q0-134-93-227t-227-93q-134 0-227 93t-93 227q0 134 93 227t227 93Zm0-320Z"/></svg>');
    --dark-tip-block-border-color: #a2ab6f;
    --dark-tip-block-background-color: #2f3023;
    --dark-tip-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23a2ab6f"><path d="M480-80q-33 0-56.5-23.5T400-160h160q0 33-23.5 56.5T480-80ZM320-200v-80h320v80H320Zm10-120q-69-41-109.5-110T180-580q0-125 87.5-212.5T480-880q125 0 212.5 87.5T780-580q0 81-40.5 150T630-320H330Zm24-80h252q45-32 69.5-79T700-580q0-92-64-156t-156-64q-92 0-156 64t-64 156q0 54 24.5 101t69.5 79Zm126 0Z"/></svg>');
    --dark-todo-block-border-color: #6fab98;
    --dark-todo-block-background-color: #23302e;
    --dark-todo-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%236fab98"><path d="M680-80q-83 0-141.5-58.5T480-280q0-83 58.5-141.5T680-480q83 0 141.5 58.5T880-280q0 83-58.5 141.5T680-80Zm67-105 28-28-75-75v-112h-40v128l87 87Zm-547 65q-33 0-56.5-23.5T120-200v-560q0-33 23.5-56.5T200-840h167q11-35 43-57.5t70-22.5q40 0 71.5 22.5T594-840h166q33 0 56.5 23.5T840-760v250q-18-13-38-22t-42-16v-212h-80v120H280v-120h-80v560h212q7 22 16 42t22 38H200Zm280-640q17 0 28.5-11.5T520-800q0-17-11.5-28.5T480-840q-17 0-28.5 11.5T440-800q0 17 11.5 28.5T480-760Z"/></svg>');
    --dark-warning-block-border-color: #ab9c6f;
    --dark-warning-block-background-color: #302b23;
    --dark-warning-block-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23ab9c6f"><path d="M109-120q-11 0-20-5.5T75-140q-5-9-5.5-19.5T75-180l370-640q6-10 15.5-15t19.5-5q10 0 19.5 5t15.5 15l370 640q6 10 5.5 20.5T885-140q-5 9-14 14.5t-20 5.5H109Zm69-80h604L480-720 178-200Zm302-40q17 0 28.5-11.5T520-280q0-17-11.5-28.5T480-320q-17 0-28.5 11.5T440-280q0 17 11.5 28.5T480-240Zm0-120q17 0 28.5-11.5T520-400v-120q0-17-11.5-28.5T480-560q-17 0-28.5 11.5T440-520v120q0 17 11.5 28.5T480-360Zm0-100Z"/></svg>');
    --dark-theme-icon: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="%23f0f0f0"><path d="M480-120q-150 0-255-105T120-480q0-150 105-255t255-105q14 0 27.5 1t26.5 3q-41 29-65.5 75.5T444-660q0 90 63 153t153 63q55 0 101-24.5t75-65.5q2 13 3 26.5t1 27.5q0 150-105 255T480-120Zm0-80q88 0 158-48.5T740-375q-20 5-40 8t-40 3q-123 0-209.5-86.5T364-660q0-20 3-40t8-40q-78 32-126.5 102T200-480q0 116 82 198t198 82Zm-10-270Z"/></svg>');

    --indent: 2.5em;
    --border-radius: 0.25em;
}

/* BEGIN LIGHT AND DARK THEME */

@media (prefers-color-scheme: light) {
    html {
        --background-color: var(--light-background-color);
        --deep-background-color: var(--light-deep-background-color);
        --text-color: var(--light-text-color);
        --border-color: var(--light-border-color);
        --table-border-color: var(--light-table-border-color);
        --del-color: var(--light-del-color);
        --del-background-color: var(--light-del-background-color);
        --ins-color: var(--light-ins-color);
        --ins-background-color: var(--light-ins-background-color);
        --para-color: var(--light-para-color);
        --a-color: var(--light-a-color);
        --a-visited-color: var(--light-a-visited-color);
        --a-hover-color: var(--light-a-hover-color);
        --mark-color: var(--light-mark-color);
        --mark-background-color: var(--light-mark-background-color);
        --abstract-border-color: var(--light-abstract-border-color);
        --abstract-background-color: var(--light-abstract-background-color);
        --abstract-image: var(--light-abstract-image);
        --blockquote-border-color: var(--light-blockquote-border-color);
        --blockquote-background-color: var(--light-blockquote-background-color);
        --blockquote-image: var(--light-blockquote-image);
        --bug-block-border-color: var(--light-bug-block-border-color);
        --bug-block-background-color: var(--light-bug-block-background-color);
        --bug-block-image: var(--light-bug-block-image);
        --decision-block-border-color: var(--light-decision-block-border-color);
        --decision-block-background-color: var(--light-decision-block-background-color);
        --decision-block-image: var(--light-decision-block-image);
        --del-block-border-color: var(--light-del-block-border-color);
        --del-block-background-color: var(--light-del-block-background-color);
        --del-block-image: var(--light-del-block-image);
        --details-border-color: var(--light-details-border-color);
        --details-background-color: var(--light-details-background-color);
        --details-image: var(--light-details-image);
        --diff-block-border-color: var(--light-diff-block-border-color);
        --diff-block-background-color: var(--light-diff-block-background-color);
        --diff-block-image: var(--light-diff-block-image);
        --example-block-border-color: var(--light-example-block-border-color);
        --example-block-background-color: var(--light-example-block-background-color);
        --example-block-image: var(--light-example-block-image);
        --important-block-border-color: var(--light-important-block-border-color);
        --important-block-background-color: var(--light-important-block-background-color);
        --important-block-image: var(--light-important-block-image);
        --ins-block-border-color: var(--light-ins-block-border-color);
        --ins-block-background-color: var(--light-ins-block-background-color);
        --ins-block-image: var(--light-ins-block-image);
        --note-block-border-color: var(--light-note-block-border-color);
        --note-block-background-color: var(--light-note-block-background-color);
        --note-block-image: var(--light-note-block-image);
        --tip-block-border-color: var(--light-tip-block-border-color);
        --tip-block-background-color: var(--light-tip-block-background-color);
        --tip-block-image: var(--light-tip-block-image);
        --todo-block-border-color: var(--light-todo-block-border-color);
        --todo-block-background-color: var(--light-todo-block-background-color);
        --todo-block-image: var(--light-todo-block-image);
        --warning-block-border-color: var(--light-warning-block-border-color);
        --warning-block-background-color: var(--light-warning-block-background-color);
        --warning-block-image: var(--light-warning-block-image);
        --theme-icon: var(--light-theme-icon);
    }
}

@media (prefers-color-scheme: dark) {
    html {
        --background-color: var(--dark-background-color);
        --deep-background-color: var(--dark-deep-background-color);
        --text-color: var(--dark-text-color);
        --border-color: var(--dark-border-color);
        --table-border-color: var(--dark-table-border-color);
        --del-color: var(--dark-del-color);
        --del-background-color: var(--dark-del-background-color);
        --ins-color: var(--dark-ins-color);
        --ins-background-color: var(--dark-ins-background-color);
        --para-color: var(--dark-para-color);
        --a-color: var(--dark-a-color);
        --a-visited-color: var(--dark-a-visited-color);
        --a-hover-color: var(--dark-a-hover-color);
        --mark-color: var(--dark-mark-color);
        --mark-background-color: var(--dark-mark-background-color);
        --abstract-border-color: var(--dark-abstract-border-color);
        --abstract-background-color: var(--dark-abstract-background-color);
        --abstract-image: var(--dark-abstract-image);
        --blockquote-border-color: var(--dark-blockquote-border-color);
        --blockquote-background-color: var(--dark-blockquote-background-color);
        --blockquote-image: var(--dark-blockquote-image);
        --bug-block-border-color: var(--dark-bug-block-border-color);
        --bug-block-background-color: var(--dark-bug-block-background-color);
        --bug-block-image: var(--dark-bug-block-image);
        --decision-block-border-color: var(--dark-decision-block-border-color);
        --decision-block-background-color: var(--dark-decision-block-background-color);
        --decision-block-image: var(--dark-decision-block-image);
        --del-block-border-color: var(--dark-del-block-border-color);
        --del-block-background-color: var(--dark-del-block-background-color);
        --del-block-image: var(--dark-del-block-image);
        --details-border-color: var(--dark-details-border-color);
        --details-background-color: var(--dark-details-background-color);
        --details-image: var(--dark-details-image);
        --diff-block-border-color: var(--dark-diff-block-border-color);
        --diff-block-background-color: var(--dark-diff-block-background-color);
        --diff-block-image: var(--dark-diff-block-image);
        --example-block-border-color: var(--dark-example-block-border-color);
        --example-block-background-color: var(--dark-example-block-background-color);
        --example-block-image: var(--dark-example-block-image);
        --important-block-border-color: var(--dark-important-block-border-color);
        --important-block-background-color: var(--dark-important-block-background-color);
        --important-block-image: var(--dark-important-block-image);
        --ins-block-border-color: var(--dark-ins-block-border-color);
        --ins-block-background-color: var(--dark-ins-block-background-color);
        --ins-block-image: var(--dark-ins-block-image);
        --note-block-border-color: var(--dark-note-block-border-color);
        --note-block-background-color: var(--dark-note-block-background-color);
        --note-block-image: var(--dark-note-block-image);
        --tip-block-border-color: var(--dark-tip-block-border-color);
        --tip-block-background-color: var(--dark-tip-block-background-color);
        --tip-block-image: var(--dark-tip-block-image);
        --todo-block-border-color: var(--dark-todo-block-border-color);
        --todo-block-background-color: var(--dark-todo-block-background-color);
        --todo-block-image: var(--dark-todo-block-image);
        --warning-block-border-color: var(--dark-warning-block-border-color);
        --warning-block-background-color: var(--dark-warning-block-background-color);
        --warning-block-image: var(--dark-warning-block-image);
        --theme-icon: var(--dark-theme-icon);
    }
}

html.light {
    --background-color: var(--light-background-color);
    --deep-background-color: var(--light-deep-background-color);
    --text-color: var(--light-text-color);
    --border-color: var(--light-border-color);
    --table-border-color: var(--light-table-border-color);
    --del-color: var(--light-del-color);
    --del-background-color: var(--light-del-background-color);
    --ins-color: var(--light-ins-color);
    --ins-background-color: var(--light-ins-background-color);
    --para-color: var(--light-para-color);
    --a-color: var(--light-a-color);
    --a-visited-color: var(--light-a-visited-color);
    --a-hover-color: var(--light-a-hover-color);
    --mark-color: var(--light-mark-color);
    --mark-background-color: var(--light-mark-background-color);
    --abstract-border-color: var(--light-abstract-border-color);
    --abstract-background-color: var(--light-abstract-background-color);
    --abstract-image: var(--light-abstract-image);
    --blockquote-border-color: var(--light-blockquote-border-color);
    --blockquote-background-color: var(--light-blockquote-background-color);
    --blockquote-image: var(--light-blockquote-image);
    --bug-block-border-color: var(--light-bug-block-border-color);
    --bug-block-background-color: var(--light-bug-block-background-color);
    --bug-block-image: var(--light-bug-block-image);
    --decision-block-border-color: var(--light-decision-block-border-color);
    --decision-block-background-color: var(--light-decision-block-background-color);
    --decision-block-image: var(--light-decision-block-image);
    --del-block-border-color: var(--light-del-block-border-color);
    --del-block-background-color: var(--light-del-block-background-color);
    --del-block-image: var(--light-del-block-image);
    --details-border-color: var(--light-details-border-color);
    --details-background-color: var(--light-details-background-color);
    --details-image: var(--light-details-image);
    --diff-block-border-color: var(--light-diff-block-border-color);
    --diff-block-background-color: var(--light-diff-block-background-color);
    --diff-block-image: var(--light-diff-block-image);
    --example-block-border-color: var(--light-example-block-border-color);
    --example-block-background-color: var(--light-example-block-background-color);
    --example-block-image: var(--light-example-block-image);
    --important-block-border-color: var(--light-important-block-border-color);
    --important-block-background-color: var(--light-important-block-background-color);
    --important-block-image: var(--light-important-block-image);
    --ins-block-border-color: var(--light-ins-block-border-color);
    --ins-block-background-color: var(--light-ins-block-background-color);
    --ins-block-image: var(--light-ins-block-image);
    --note-block-border-color: var(--light-note-block-border-color);
    --note-block-background-color: var(--light-note-block-background-color);
    --note-block-image: var(--light-note-block-image);
    --tip-block-border-color: var(--light-tip-block-border-color);
    --tip-block-background-color: var(--light-tip-block-background-color);
    --tip-block-image: var(--light-tip-block-image);
    --todo-block-border-color: var(--light-todo-block-border-color);
    --todo-block-background-color: var(--light-todo-block-background-color);
    --todo-block-image: var(--light-todo-block-image);
    --warning-block-border-color: var(--light-warning-block-border-color);
    --warning-block-background-color: var(--light-warning-block-background-color);
    --warning-block-image: var(--light-warning-block-image);
    --theme-icon: var(--light-theme-icon);
}

html.dark {
    --background-color: var(--dark-background-color);
    --deep-background-color: var(--dark-deep-background-color);
    --text-color: var(--dark-text-color);
    --border-color: var(--dark-border-color);
    --table-border-color: var(--dark-table-border-color);
    --del-color: var(--dark-del-color);
    --del-background-color: var(--dark-del-background-color);
    --ins-color: var(--dark-ins-color);
    --ins-background-color: var(--dark-ins-background-color);
    --para-color: var(--dark-para-color);
    --a-color: var(--dark-a-color);
    --a-visited-color: var(--dark-a-visited-color);
    --a-hover-color: var(--dark-a-hover-color);
    --mark-color: var(--dark-mark-color);
    --mark-background-color: var(--dark-mark-background-color);
    --abstract-border-color: var(--dark-abstract-border-color);
    --abstract-background-color: var(--dark-abstract-background-color);
    --abstract-image: var(--dark-abstract-image);
    --blockquote-border-color: var(--dark-blockquote-border-color);
    --blockquote-background-color: var(--dark-blockquote-background-color);
    --blockquote-image: var(--dark-blockquote-image);
    --bug-block-border-color: var(--dark-bug-block-border-color);
    --bug-block-background-color: var(--dark-bug-block-background-color);
    --bug-block-image: var(--dark-bug-block-image);
    --decision-block-border-color: var(--dark-decision-block-border-color);
    --decision-block-background-color: var(--dark-decision-block-background-color);
    --decision-block-image: var(--dark-decision-block-image);
    --del-block-border-color: var(--dark-del-block-border-color);
    --del-block-background-color: var(--dark-del-block-background-color);
    --del-block-image: var(--dark-del-block-image);
    --details-border-color: var(--dark-details-border-color);
    --details-background-color: var(--dark-details-background-color);
    --details-image: var(--dark-details-image);
    --diff-block-border-color: var(--dark-diff-block-border-color);
    --diff-block-background-color: var(--dark-diff-block-background-color);
    --diff-block-image: var(--dark-diff-block-image);
    --example-block-border-color: var(--dark-example-block-border-color);
    --example-block-background-color: var(--dark-example-block-background-color);
    --example-block-image: var(--dark-example-block-image);
    --important-block-border-color: var(--dark-important-block-border-color);
    --important-block-background-color: var(--dark-important-block-background-color);
    --important-block-image: var(--dark-important-block-image);
    --ins-block-border-color: var(--dark-ins-block-border-color);
    --ins-block-background-color: var(--dark-ins-block-background-color);
    --ins-block-image: var(--dark-ins-block-image);
    --note-block-border-color: var(--dark-note-block-border-color);
    --note-block-background-color: var(--dark-note-block-background-color);
    --note-block-image: var(--dark-note-block-image);
    --tip-block-border-color: var(--dark-tip-block-border-color);
    --tip-block-background-color: var(--dark-tip-block-background-color);
    --tip-block-image: var(--dark-tip-block-image);
    --todo-block-border-color: var(--dark-todo-block-border-color);
    --todo-block-background-color: var(--dark-todo-block-background-color);
    --todo-block-image: var(--dark-todo-block-image);
    --warning-block-border-color: var(--dark-warning-block-border-color);
    --warning-block-background-color: var(--dark-warning-block-background-color);
    --warning-block-image: var(--dark-warning-block-image);
    --theme-icon: var(--dark-theme-icon);
}

/* END LIGHT AND DARK THEME */

html {
    margin: 0;
    width: 100%;
    font-family: var(--serif-family);
    font-size: 11pt;

    border-left: var(--border-thickness) solid var(--border-color);
    color: var(--text-color);
    background-color: var(--background-color);
}

body {
    --vertical-margin: 2rem;
    --margin-left: 3rem;
    --margin-right: 2rem;

    margin: var(--vertical-margin) var(--margin-right) var(--vertical-margin) var(--margin-left);
    width: calc(100% - var(--margin-left) - var(--margin-right));
    box-sizing: border-box;
}

main {
    max-width: 60rem;
    margin-left: auto;
    margin-right: auto;
}

p {
    text-align: justify;
}

abstract-block,
blockquote,
bug-block,
code-block,
decision-block,
del-block,
details,
dl,
diff-block,
example-block,
hr,
ol,
important-block,
ins-block,
math[display=block],
note-block,
p,
pre,
tip-block,
todo-block,
ul,
warning-block,
.indent {
    display: block;
    margin-top: 1em;
    margin-bottom: 1em;
}

a {
    color: var(--a-color);
    text-decoration: unset;
}

a:visited {
    color: var(--a-visited-color);
}

a:hover,
a:focus {
    color: var(--a-hover-color);
}

a:hover {
    text-decoration: underline;
}

ol,
ul {
    padding-left: var(--indent);
}

li {
    margin: 0.5em 0;
}

dt {
    margin-top: 0.25em;
    font-style: italic;
    font-weight: bold;
}

dd {
    margin-bottom: 0.25em;
    margin-left: var(--indent);
}

abstract-block,
blockquote,
bug-block,
del-block,
details,
decision-block,
diff-block,
example-block,
important-block,
ins-block,
note-block,
tip-block,
todo-block,
warning-block {
    --border-thickness: 0.25em;
    --padding: 0.5em;

    position: relative;
    width: calc(100% - var(--indent));
    box-sizing: border-box;
    padding: var(--padding);
    margin-left: var(--indent);

    border-top-right-radius: var(--border-radius);
    border-bottom-right-radius: var(--border-radius);
}

abstract-block>:first-child,
blockquote>:first-child,
bug-block>:first-child,
del-block>:first-child,
details>:first-child,
decision-block>:first-child,
diff-block>:first-child,
example-block>:first-child,
important-block>:first-child,
ins-block>:first-child,
note-block>:first-child,
tip-block>:first-child,
todo-block>:first-child,
warning-block>:first-child {
    margin-top: 0;
}

abstract-block>:last-child,
blockquote>:last-child,
bug-block>:last-child,
del-block>:last-child,
details>:last-child,
decision-block>:last-child,
diff-block>:last-child,
example-block>:last-child,
important-block>:last-child,
ins-block>:last-child,
note-block>:last-child,
todo-block>:last-child,
tip-block>:last-child,
warning-block>:last-child {
    margin-bottom: 0;
}

abstract-block::before,
blockquote::before,
bug-block::before,
del-block::before,
details::before,
decision-block::before,
diff-block::before,
example-block::before,
important-block::before,
ins-block::before,
note-block::before,
todo-block::before,
tip-block::before,
warning-block::before {
    position: absolute;
    left: -2.5em;
    top: 0.25em;
    width: 2em;
    height: 2em;

    content: "";
    display: inline-block;
    background-size: contain;
    background-repeat: no-repeat;

}

code,
code-block,
pre,
samp,
tt,
tt-,
.mono {
    font-family: var(--monospace-family);
    font-style: normal;
    font-variant-ligatures: none;
}

code-block:not(.borderless),
pre {
    padding: 0.5em;
    border-radius: var(--border-radius);
    box-sizing: border-box;

    background-color: var(--deep-background-color);
    border: 1px solid var(--border-color);
}

code-block,
pre {
    font-size: 95%;
    width: 100%;
}

code-block,
pre {
    white-space: pre;
    overflow-x: auto;
}

/* INSERTIONS AND DELETIONS */

ins,
ins-lines {
    text-decoration: underline;
    font-weight: 600;
    color: var(--ins-color);
    background-color: var(--ins-background-color);
}

code-block ins,
code-block ins-lines {
    text-decoration: inherit;
}

del {
    text-decoration: line-through;
}

del,
del-lines {
    color: var(--del-color);
    background-color: var(--del-background-color);
}

ins-lines,
del-lines {
    display: inline-block;
    width: 100%;
}

ins h-,
ins-lines h-,
del h-,
del-lines h- {
    color: inherit !important;
    background-color: inherit !important;
}

kbd {
    font-family: var(--sans-serif-family);

    display: inline-block;
    padding: 0 0.25em 0.15em 0.25em;
    border-radius: 0.25em;
    white-space: nowrap;

    background-color: var(--deep-background-color);
    border: 1px solid var(--border-color);
    box-shadow: inset 0 -0.1em 0 var(--border-color);
}

mark {
    color: var(--mark-color);
    background-color: var(--mark-background-color);
}

math:not([display=block]) {
    font-size: 120%;
}

math[display=block] {
    width: fit-content;
    margin-left: var(--indent);

    font-size: 110%;
}

g-term,
f-sans,
f-serif,
wg21-block {
    display: inline;
}

f-sans,
.sans {
    font-family: var(--sans-serif-family);
}

f-serif,
.serif {
    font-family: var(--serif-family);
}

.grammar dd,
g-term {
    font-family: var(--sans-serif-family);
    font-style: oblique;
}

.grammar {
    margin-left: var(--indent);
}

.grammar dt {
    font-weight: normal;
    font-style: normal;
}

.oblique {
    font-style: oblique;
}

.word {
    white-space: nowrap;
}

.wg21-head {
    margin-bottom: 4em;
}

.wg21-head dl {
    font-family: var(--sans-serif-family);
}

.wg21-head dt {
    font-style: normal;
}

/* HEADINGS */

h1,
h2,
h3,
h4,
h5,
h6 {
    position: relative;
    margin: 1rem 0;
}

h1 {
    margin: 2rem 0 1.5rem 0;
    font-size: 250%;
}

h2 {
    margin: 2.5rem 0 1.5rem 0;
    font-size: 166%;
}

h3 {
    margin: 2rem 0 1rem 0;
    font-size: 133%;
}

h4 {
    margin: 1.5rem 0 0.5rem 0;
    font-size: 100%;
}

h5 {
    margin: 1rem 0 0.5rem 0;
    font-size: 100%;
    font-weight: normal;
}

h6 {
    margin: 1rem 0 0.5rem 0;
    font-size: 90%;
    font-weight: normal;
}

table {
    --border: 1px solid var(--table-border-color);

    margin-top: 1em;
    margin-bottom: 1em;
    border-collapse: collapse;
}

table,
tbody,
thead,
th {
    border: var(--border);
}

td {
    border-left: var(--border);
    border-right: var(--border);
}

td,
th {
    padding: 0.1em 0.5em;
}

.para {
    cursor: pointer;
    font-weight: normal;
    font-family: var(--monospace-family);
    text-decoration: none;
    opacity: 0.25;

    position: absolute;
    top: 0.05em;
    left: calc(-1rem - 0.5ch);
}

.para,
.para::before {
    color: var(--para-color);
}

.para:hover,
.para:focus,
:target .para {
    opacity: 1;
}

.para::before {
    content: "§";
}

/* TABLE OF CONTENTS */

.toc {
    --h-indent: 0.75em;

    display: grid;
    grid-template-columns: min-content auto;
}

.toc-num {
    display: inline-block;
    align-self: end;
    padding-right: 3em;

    letter-spacing: 0em;
}

.toc h1,
.toc h2,
.toc h3,
.toc h4,
.toc h5,
.toc h6 {
    display: inline-block;

    font-weight: 500;
    font-size: 12pt;

    margin-top: 0;
    margin-bottom: 0;
}

.toc a,
.toc-num {
    border-bottom: 1px solid rgba(0, 0, 0, 0);
    color: var(--text-color);
}

.toc h1,
.toc-num[data-level="1"] {
    font-size: 125%;
    font-weight: 900;
}

.toc h2,
.toc-num[data-level="2"] {
    font-weight: 700;
}

.toc h3,
.toc-num[data-level="3"] {
    font-weight: 500;
}

.toc h4,
.toc-num[data-level="4"] {
    font-size: 95%;
    font-weight: 400;
}

.toc h5,
.toc-num[data-level="5"] {
    font-size: 90%;
    font-weight: 300;
}

.toc h6,
.toc-num[data-level="6"] {
    font-size: 90%;
    font-weight: 100;
}

.toc a:hover {
    display: inline-block;
    width: 100%;

    color: var(--a-hover-color);
    border-bottom: 1px dashed var(--a-hover-color);
}

.toc h1:not(:nth-child(2)>h1) {
    margin-top: 1.5em;
}

.toc h2:not(:nth-child(2)>h2) {
    margin-top: 0.75em;
}

/** BIBLIOGRAPHY */

.bib {
    display: block;
    margin: 1em 0;
}

.bib-item {
    display: inline-block;
    width: 100%;
    margin: 0.25em 0;
}

.bib-item>* {
    padding: 0 0.125em;
}

.bib-author {
    font-style: italic;
}

.bib-title {
    font-weight: 500;
}

.bib-date {
    font-family: var(--monospace-family);
}

.bib-date::before {
    font-family: var(--serif-family);
    content: "(";
}

.bib-date::after {
    font-family: var(--serif-family);
    content: ")";
}

.bib-link {
    display: block;
    margin-left: var(--indent);

    font-family: var(--sans-serif-family);
    font-style: normal;
}

/* SPECIAL BLOCKS */

intro- {
    display: inline-block;

    font-weight: 600;
    text-transform: uppercase;
    font-family: var(--sans-serif-family);
}

abstract-block {
    background-color: var(--abstract-background-color);
    border-left: var(--border-thickness) solid var(--abstract-border-color);
}

abstract-block::before {
    background-image: var(--abstract-image);
}

abstract-block intro-::before {
    content: "Abstract:";
    color: var(--abstract-border-color);
}

blockquote {
    background-color: var(--blockquote-background-color);
    border-left: var(--border-thickness) solid var(--blockquote-border-color);
}

blockquote::before {
    background-image: var(--blockquote-image);
    top: -0.25em;
}

blockquote intro-::before {
    content: "Quote:";
    color: var(--blockquote-border-color);
}

bug-block {
    background-color: var(--bug-block-background-color);
    border-left: var(--border-thickness) solid var(--bug-block-border-color);
}

bug-block::before {
    background-image: var(--bug-block-image);
}

bug-block intro-::before {
    content: "Bug:";
    color: var(--bug-block-border-color);
}

del-block {
    background-color: var(--del-block-background-color);
    border-left: var(--border-thickness) solid var(--del-block-border-color);
    color: var(--del-color);
}

del-block::before {
    background-image: var(--del-block-image);
}

del-block intro-::before {
    content: "Deleted:";
    color: var(--del-block-border-color);
}

del-block code,
del-block code-block {
    color: var(--text-color);
}

details {
    background-color: var(--details-background-color);
    border-left: var(--border-thickness) solid var(--details-border-color);
}

details::before {
    background-image: var(--details-image);
}

summary {
    font-family: var(--sans-serif-family);
    color: var(--details-border-color);
    user-select: none;
    cursor: pointer;
}

details[open]>summary {
    margin-bottom: 0.5em;
}

decision-block {
    background-color: var(--decision-block-background-color);
    border-left: var(--border-thickness) solid var(--decision-block-border-color);
}

decision-block::before {
    background-image: var(--decision-block-image);
}

decision-block intro-::before {
    content: "Decision:";
    color: var(--decision-block-border-color);
}

diff-block {
    background-color: var(--diff-block-background-color);
    border-left: var(--border-thickness) solid var(--diff-block-border-color);
}

diff-block::before {
    background-image: var(--diff-block-image);
}

diff-block intro-::before {
    content: "Difference:";
    color: var(--diff-block-border-color);
}

example-block {
    background-color: var(--example-block-background-color);
    border-left: var(--border-thickness) solid var(--example-block-border-color);
}

example-block::before {
    background-image: var(--example-block-image);
}

example-block intro-::before {
    content: "Example:";
    color: var(--example-block-border-color);
}

important-block {
    background-color: var(--important-block-background-color);
    border-left: var(--border-thickness) solid var(--important-block-border-color);
}

important-block::before {
    background-image: var(--important-block-image);
}

important-block intro-::before {
    content: "Important:";
    color: var(--important-block-border-color);
}

ins-block {
    background-color: var(--ins-block-background-color);
    border-left: var(--border-thickness) solid var(--ins-block-border-color);
    color: var(--ins-color);
}

ins-block code,
ins-block code-block {
    color: var(--text-color);
}

ins-block::before {
    background-image: var(--ins-block-image);
}

ins-block intro-::before {
    content: "Inserted:";
    color: var(--ins-block-border-color);
}

note-block {
    background-color: var(--note-block-background-color);
    border-left: var(--border-thickness) solid var(--note-block-border-color);
}

note-block::before {
    background-image: var(--note-block-image);
}

note-block intro-::before {
    content: "Note:";
    color: var(--note-block-border-color);
}

tip-block {
    background-color: var(--tip-block-background-color);
    border-left: var(--border-thickness) solid var(--tip-block-border-color);
}

tip-block::before {
    background-image: var(--tip-block-image);
}

tip-block intro-::before {
    content: "Tip:";
    color: var(--tip-block-border-color);
}

todo-block {
    background-color: var(--todo-block-background-color);
    border-left: var(--border-thickness) solid var(--todo-block-border-color);
}

todo-block::before {
    background-image: var(--todo-block-image);
}

todo-block intro-::before {
    content: "Todo:";
    color: var(--todo-block-border-color);
}

warning-block {
    background-color: var(--warning-block-background-color);
    border-left: var(--border-thickness) solid var(--warning-block-border-color);
}

warning-block::before {
    background-image: var(--warning-block-image);
}

warning-block intro-::before {
    content: "Warning:";
    color: var(--warning-block-border-color);
}

.indent {
    margin-left: var(--indent);
}

/* SETTINGS MENU */

#settings:not(.js) {
    display: none;
}

#settings {
    z-index: 999;
    position: fixed;
    display: inline-block;
    top: 1em;
    right: 1em;
}

#theme-icon {
    display: block;
    width: 2.5em;
    height: 2.5em;
    cursor: pointer;
    background-image: var(--theme-icon);
    background-size: contain;
    opacity: 0.25;
}

#theme-icon:hover,
#theme-icon:focus {
    opacity: 1;
}
  </style>
  <style>
@media (prefers-color-scheme: light) {
h-[data-h^=err] { color:#ff0000; }
h-[data-h^=cmt] { color:green; font-style:italic; }
h-[data-h^=cmt_dlim] { font-style:normal; }
h-[data-h^=val] { color:#9f6807; }
h-[data-h^=num] { color:#9f6807; }
h-[data-h^=str] { color:#9f6807; }
h-[data-h^=esc] { color:#9f6807; }
h-[data-h^=null] { color:#00607c; }
h-[data-h^=bool] { color:#9f6807; }
h-[data-h^=this] { color:#00607c; }
h-[data-h^=mac] { color:#6f4e37; }
h-[data-h^=id] { color:#000000; }
h-[data-h^=id_labl] { color:#517a0b; }
h-[data-h^=kw] { color:#00607c; }
h-[data-h^=sym] { color:#570057; }
h-[data-h^=sym_punc] { color:#000000; }
h-[data-h^=sym_par] { color:#af1915; }
h-[data-h^=sym_sqr] { color:#af1915; }
h-[data-h^=sym_brac] { color:#af1915; }
h-[data-h^=diff_head] { color:#777777; }
h-[data-h^=diff_head_hunk] { color:#5c477e; }
h-[data-h^=diff_eq] { color:#000000; }
h-[data-h^=diff_del] { color:#b31d28; background-color:#ffeef0; }
h-[data-h^=diff_ins] { color:#22863a; background-color:#f0fff4; }
h-[data-h^=diff_mod] { color:#7a680d; background-color:#fffdee; }
h-[data-h^=mk_tag] { color:#00607c; }
h-[data-h^=mk_attr] { color:#5c477e; }
h-[data-h^=mk_del] { color:#ce9178; text-decoration:line-through; }
h-[data-h^=mk_ins] { color:#b5cea8; text-decoration:underline; }
h-[data-h^=mk_emph] { font-style:italic; }
h-[data-h^=mk_stro] { font-weight:bold; }
h-[data-h^=mk_emph_stro] { font-style:italic; font-weight:bold; }
h-[data-h^=mk_ulin] { text-decoration:underline; }
h-[data-h^=mk_emph_ulin] { font-style:italic; text-decoration:underline; }
h-[data-h^=mk_stro_ulin] { font-weight:bold; text-decoration:underline; }
h-[data-h^=mk_emph_stro_ulin] { font-weight:bold; font-style:italic; text-decoration:underline; }
h-[data-h^=mk_strk] { text-decoration:line-through; }
h-[data-h^=mk_emph_strk] { font-style:italic; text-decoration:line-through; }
h-[data-h^=mk_stro_strk] { font-weight:bold; text-decoration:line-through; }
h-[data-h^=mk_emph_stro_strk] { font-weight:bold; font-style:italic; text-decoration:line-through; }
h-[data-h^=mk_ulin_strk] { text-decoration:underline line-through; }
h-[data-h^=mk_emph_ulin_strk] { font-style:italic; text-decoration:underline line-through; }
h-[data-h^=mk_stro_ulin_strk] { font-weight:bold; text-decoration:underline line-through; }
h-[data-h^=mk_emph_stro_ulin_strk] { font-weight:bold; font-style:italic; text-decoration:underline line-through; }
h-[data-h^=sh_cmd] { color:#00607c; }
h-[data-h^=sh-opt] { color:#000000; }
h-[data-h^=asm_ins] { color:#00607c; }
h-[data-h^=asm_ins_psu] { color:#9f6807; }
}
@media (prefers-color-scheme: dark) {
h-[data-h^=err] { color:#ff0000; }
h-[data-h^=cmt] { color:#a2e08d; font-style:italic; }
h-[data-h^=cmt_dlim] { font-style:normal; }
h-[data-h^=val] { color:#f2d18d; }
h-[data-h^=num] { color:#f2d18d; }
h-[data-h^=num_dlim] { color:#e6b191; }
h-[data-h^=num_deco] { color:#e6b191; }
h-[data-h^=str] { color:#f2d18d; }
h-[data-h^=str_dlim] { color:#e6b191; }
h-[data-h^=str_deco] { color:#e6b191; }
h-[data-h^=esc] { color:#e6aee6; }
h-[data-h^=null] { color:#62ded6; }
h-[data-h^=bool] { color:#f2d18d; }
h-[data-h^=this] { color:#62ded6; }
h-[data-h^=mac] { color:#cc946e; }
h-[data-h^=id] { color:#f0f0f0; }
h-[data-h^=id_labl] { color:#d8eda6; }
h-[data-h^=kw] { color:#62ded6; }
h-[data-h^=sym] { color:#baa6b9; }
h-[data-h^=sym_punc] { color:#d0d0d0; }
h-[data-h^=sym_par] { color:#fa7878; }
h-[data-h^=sym_sqr] { color:#fa7878; }
h-[data-h^=sym_brac] { color:#fa7878; }
h-[data-h^=diff_head] { color:#777777; }
h-[data-h^=diff_head_hunk] { color:#edc385; }
h-[data-h^=diff_eq] { color:#e7e7e7; }
h-[data-h^=diff_del] { color:#ffdcd7; background-color:#67060c; }
h-[data-h^=diff_ins] { color:#aff5b4; background-color:#033a16; }
h-[data-h^=diff_mod] { color:#fff4d7; background-color:#674d06; }
h-[data-h^=mk_tag] { color:#62ded6; }
h-[data-h^=mk_attr] { color:#a4c4de; }
h-[data-h^=mk_del] { color:#ce9178; text-decoration:line-through; }
h-[data-h^=mk_ins] { color:#b5cea8; text-decoration:underline; }
h-[data-h^=mk_emph] { font-style:italic; }
h-[data-h^=mk_stro] { font-weight:bold; }
h-[data-h^=mk_emph_stro] { font-style:italic; font-weight:bold; }
h-[data-h^=mk_ulin] { text-decoration:underline; }
h-[data-h^=mk_emph_ulin] { font-style:italic; text-decoration:underline; }
h-[data-h^=mk_stro_ulin] { font-weight:bold; text-decoration:underline; }
h-[data-h^=mk_emph_stro_ulin] { font-weight:bold; font-style:italic; text-decoration:underline; }
h-[data-h^=mk_strk] { text-decoration:line-through; }
h-[data-h^=mk_emph_strk] { font-style:italic; text-decoration:line-through; }
h-[data-h^=mk_stro_strk] { font-weight:bold; text-decoration:line-through; }
h-[data-h^=mk_emph_stro_strk] { font-weight:bold; font-style:italic; text-decoration:line-through; }
h-[data-h^=mk_ulin_strk] { text-decoration:underline line-through; }
h-[data-h^=mk_emph_ulin_strk] { font-style:italic; text-decoration:underline line-through; }
h-[data-h^=mk_stro_ulin_strk] { font-weight:bold; text-decoration:underline line-through; }
h-[data-h^=mk_emph_stro_ulin_strk] { font-weight:bold; font-style:italic; text-decoration:underline line-through; }
h-[data-h^=sh_cmd] { color:#62ded6; }
h-[data-h^=sh-opt] { color:#f0f0f0; }
h-[data-h^=asm_ins] { color:#62ded6; }
h-[data-h^=asm_ins_psu] { color:#e6aee6; }
}

html.light h-[data-h^=err] { color:#ff0000; }
html.light h-[data-h^=cmt] { color:green; font-style:italic; }
html.light h-[data-h^=cmt_dlim] { font-style:normal; }
html.light h-[data-h^=val] { color:#9f6807; }
html.light h-[data-h^=num] { color:#9f6807; }
html.light h-[data-h^=str] { color:#9f6807; }
html.light h-[data-h^=esc] { color:#9f6807; }
html.light h-[data-h^=null] { color:#00607c; }
html.light h-[data-h^=bool] { color:#9f6807; }
html.light h-[data-h^=this] { color:#00607c; }
html.light h-[data-h^=mac] { color:#6f4e37; }
html.light h-[data-h^=id] { color:#000000; }
html.light h-[data-h^=id_labl] { color:#517a0b; }
html.light h-[data-h^=kw] { color:#00607c; }
html.light h-[data-h^=sym] { color:#570057; }
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<p><div class=wg21-head><h1>A utility function for propagating the most significant bit</h1>

<dl>
    <dt>Document number:</dt> <dd><a href=https://wg21%2elink/P3764R0>P3764R0</a></dd>
    <dt>Date:</dt>            <dd><tt->2025-07-15</tt-></dd>
    <dt>Audience:</dt>        <dd>SG6</dd>
    <dt>Project:</dt>         <dd>ISO/IEC 14882 Programming Languages — C++, ISO/IEC JTC1/SC22/WG21</dd>
    <dt>Reply-to:</dt>        <dd>Jan Schultke &lt;<a href=mailto:janschultke@gmail%2ecom class=sans>janschultke@gmail.com</a>&gt;</dd>
    <dt>GitHub Issue:</dt>    <dd><a href=https://wg21%2elink/P3764/github class=sans>wg21.link/P3764/github</a></dd>
    <dt>Source:</dt>          <dd><a href=https://github%2ecom/Eisenwave/cpp-proposals/blob/master/src/msb-to-mask%2ecow class=sans>github.com/Eisenwave/cpp-proposals/blob/master/src/msb-to-mask.cow</a></dd>
</dl>
<hr/>
</div></p>

<abstract-block><p><intro-></intro-> 
Add a function to the <code><h- data-h=str>&lt;bit&gt;</h-></code> header
which converts the most significant bit to a bit mask.
</p></abstract-block>

<h2 id=contents><a class=para href=#contents></a>Contents</h2>

<div class=toc><div class=toc-num data-level=2>1</div>
<a href=#introduction><h2>Introduction</h2></a>
<div class=toc-num data-level=3>1.1</div>
<a href=#this-mask-creation-needs-a-function><h3>This mask creation needs a function</h3></a>
<div class=toc-num data-level=2>2</div>
<a href=#motivation><h2>Motivation</h2></a>
<div class=toc-num data-level=2>3</div>
<a href=#design><h2>Design</h2></a>
<div class=toc-num data-level=3>3.1</div>
<a href=#support-for-signed-and-unsigned-types><h3>Support for signed and unsigned types</h3></a>
<div class=toc-num data-level=3>3.2</div>
<a href=#naming><h3>Naming</h3></a>
<div class=toc-num data-level=3>3.3</div>
<a href=#simd-support><h3>SIMD support</h3></a>
<div class=toc-num data-level=2>4</div>
<a href=#implementation><h2>Implementation</h2></a>
<div class=toc-num data-level=2>5</div>
<a href=#wording><h2>Wording</h2></a>
<div class=toc-num data-level=3>5.1</div>
<a href=#bit><h3>[bit]</h3></a>
<div class=toc-num data-level=3>5.2</div>
<a href=#simd><h3>[simd]</h3></a>
<div class=toc-num data-level=2>6</div>
<a href=#references><h2>References</h2></a>
</div>

<h2 id=introduction><a class=para href=#introduction></a>1. Introduction</h2>

<p>In bit manipulation,
it is a common technique to propagate the uppermost bit to all the other bits,
creating a "bit mask".
This bit mask can then be used to make an otherwise branching operation branchless.
</p>
<example-block><p><intro-></intro-> 
The following two functions for computing the positive remainder
(assuming <code><h- data-h=id>y</h-></code> is positive) are equivalent:
</p><code-block><h- data-h=cmt_dlim>//</h-><h- data-h=cmt> </h-><f-serif><h- data-h=cmt>Naive implementation</h-></f-serif>
<h- data-h=kw_type>int</h-> <h- data-h=id>mod_naive</h-><h- data-h=sym_par>(</h-><h- data-h=kw_type>int</h-> <h- data-h=id>x</h-><h- data-h=sym_punc>,</h-> <h- data-h=kw_type>int</h-> <h- data-h=id>y</h-><h- data-h=sym_par>)</h-> <h- data-h=sym_brac>{</h->
  <h- data-h=kw_type>int</h-> <h- data-h=id>rem</h-> <h- data-h=sym_op>=</h-> <h- data-h=id>x</h-> <h- data-h=sym_op>%</h-> <h- data-h=id>y</h-><h- data-h=sym_punc>;</h->
  <h- data-h=kw_ctrl>if</h-> <h- data-h=sym_par>(</h-><h- data-h=id>rem</h-> <h- data-h=sym_op>&lt;</h-> <h- data-h=num>0</h-><h- data-h=sym_par>)</h-> <h- data-h=id>rem</h-> <h- data-h=sym_op>+=</h-> <h- data-h=id>y</h-><h- data-h=sym_punc>;</h->
  <h- data-h=kw_ctrl>return</h-> <h- data-h=id>rem</h-><h- data-h=sym_punc>;</h->
<h- data-h=sym_brac>}</h->

<h- data-h=cmt_dlim>//</h-><h- data-h=cmt> </h-><f-serif><h- data-h=cmt>Branchless implementation</h-></f-serif>
<h- data-h=kw_type>int</h-> <h- data-h=id>mod_branchless</h-><h- data-h=sym_par>(</h-><h- data-h=kw_type>int</h-> <h- data-h=id>x</h-><h- data-h=sym_punc>,</h-> <h- data-h=kw_type>int</h-> <h- data-h=id>y</h-><h- data-h=sym_par>)</h-> <h- data-h=sym_brac>{</h->
  <h- data-h=kw_type>int</h-> <h- data-h=id>rem</h-> <h- data-h=sym_op>=</h-> <h- data-h=id>x</h-> <h- data-h=sym_op>%</h-> <h- data-h=id>y</h-><h- data-h=sym_punc>;</h->
  <h- data-h=id>rem</h-> <h- data-h=sym_op>+=</h-> <h- data-h=id>y</h-> <h- data-h=sym_op>&amp;</h-> <h- data-h=sym_par>(</h-><h- data-h=id>rem</h-> <h- data-h=sym_op>&gt;&gt;</h-> <h- data-h=sym_par>(</h-><h- data-h=id>INT_WIDTH</h-> <h- data-h=sym_op>-</h-> <h- data-h=num>1</h-><h- data-h=sym_par>)</h-><h- data-h=sym_par>)</h-><h- data-h=sym_punc>;</h->
  <h- data-h=kw_ctrl>return</h-> <h- data-h=id>rem</h-><h- data-h=sym_punc>;</h->
<h- data-h=sym_brac>}</h-></code-block>
</example-block>

<p>Modern optimizing compilers often find such optimizations already,
at least in simple examples like the one above.
In fact, Clang optimizes both functions the same for x86_64.
However:
</p>
<ul>
  <li>
    In larger examples, this becomes much less reliable,
    and <code><h- data-h=sym_op>&amp;&amp;</h-></code> and <code><h- data-h=kw_ctrl>if</h-></code> do get translated into conditional jumps.
  </li>
  <li>
    Compilers only perform this transformation if it heuristically better.
    Branchless programming is often applied in scenarios where code must be
    protected against timing-based side channel attacks,
    and so branchless variants may be preferred even at an extra cost.
  </li>
  <li>
    Even modern optimizing compilers miss optimizations like these sometimes.
  </li>
</ul>

<p>Therefore, using this masking technique directly is not obsolete.
You can find many examples of this technique being used at <a href="https://graphics%2estanford%2eedu/~seander/bithacks%2ehtml">[BitTwiddlingHacks]</a>
by searching for <code><h- data-h=kw>sizeof</h-></code> on that page.
</p>
<h3 id=this-mask-creation-needs-a-function><a class=para href=#this-mask-creation-needs-a-function></a>1.1. This mask creation needs a function</h3>

<p>Creating a bit mask from the sign bit by hand is especially tedious
compared to many other techniques in bit manipulation,
at least when written directly using an arithmetic right-shift.
That is because it requires right-shifting by the operand width minus one.
In generic code that is meant to operate on different integer types,
this requires use of <code><h- data-h=id>std</h-><h- data-h=sym_op>::</h-><h- data-h=id>numeric_limits</h-><h- data-h=sym_op>&lt;</h-><h- data-h=id>T</h-><h- data-h=sym_op>&gt;</h-><h- data-h=sym_op>::</h-><h- data-h=id>digits</h-></code>,
which is quite verbose and difficult to use
because it returns different results for signed and unsigned types.
</p>
<p>Another possible way to make such a mask (for signed types only)
is to write <code><h- data-h=sym_par>(</h-><h- data-h=id>x</h-> <h- data-h=sym_op>&lt;</h-> <h- data-h=num>0</h-> <h- data-h=sym_op>?</h-> <h- data-h=sym_op>-</h-><h- data-h=num>1</h-> <h- data-h=sym_punc>:</h-> <h- data-h=num>0</h-><h- data-h=sym_par>)</h-></code>,
but this reintroduces reliance on the compiler to eliminate branches.
It also doesn't express directly what is emitted by the compiler,
and in the context of bit manipulation,
keeping code "close to hardware" is often desirable.
</p>
<p>Regardless of the implementation details,
C++ users sometimes create a utility function/macro that performs sign-masking.
<a href="https://github%2ecom/search?q=-is%253Afork+language%253AC%252B%252B++++%2522sign_mask%2528%2522&type=code">[GitHubCodeSearch]</a> for <tt->-is:fork language:C++ "sign_mask("</tt->
reveals that ~8000 files already use a function called <code><h- data-h=id>sign_mask</h-></code>,
although not all of these functions have the functionality proposed here.
</p>
<p>It would be nice if this function was provided by the standard already.
</p>
<h2 id=motivation><a class=para href=#motivation></a>2. Motivation</h2>

<p>A sign-masking function should be included in the <code><h- data-h=str>&lt;bit&gt;</h-></code> header because
</p>
<ul>
  <li>
    it is a useful utility, similar to <code><h- data-h=id>has_single_bit</h-></code> and <code><h- data-h=id>bit_ceil</h-></code>,
  </li>
  <li>
    C++ users sometimes make this function/macro themselves already,
  </li>
  <li>
    there is some disagreement over how to write it,
    and the specifics may depend on hardware capabilities,
  </li>
  <li>
    the technique is sometimes used in SIMD as well,
    and the implementation using comparison to zero is "closer to hardware"
    in that context;
    however, it is still the same operation, and a common SIMD/non-SIMD spelling
    would be more expressive, and
  </li>
  <li>
    writing this function correctly, generically,
    is tedious when using <code><h- data-h=id>std</h-><h- data-h=sym_op>::</h-><h- data-h=id>numeric_limits</h-></code>.
  </li>
</ul>

<h2 id=design><a class=para href=#design></a>3. Design</h2>

<h3 id=support-for-signed-and-unsigned-types><a class=para href=#support-for-signed-and-unsigned-types></a>3.1. Support for signed and unsigned types</h3>

<p>As shown in the example in <a href=#introduction>§1. Introduction</a>,
this function is sometimes used with signed types,
not just with unsigned types.
That is why it should accept both.
</p>
<p>Such an interface would be somewhat inconsistent with the remaining functions in <code><h- data-h=str>&lt;bit&gt;</h-></code>,
but permitting the use of signed types within <code><h- data-h=str>&lt;bit&gt;</h-></code> <em>in general</em>
is not within the scope of this paper.
To my knowledge,
another SG6 proposal which proposes use of signed types in <code><h- data-h=str>&lt;bit&gt;</h-></code>
is already being developed.
</p>
<h3 id=naming><a class=para href=#naming></a>3.2. Naming</h3>

<p>I propose the name <code><h- data-h=id>std</h-><h- data-h=sym_op>::</h-><h- data-h=id>msb_to_mask</h-></code>
because it expresses its effects very clearly:
</p>
<blockquote>
<p><code><h- data-h=id>std</h-><h- data-h=sym_op>::</h-><h- data-h=id>msb_to_mask</h-></code> converts the most significant bit (MSB)
into a bit-mask.
</p></blockquote>

<p>The function should behave bitwise-equivalently for signed and unsigned types,
so including <code><h- data-h=id>sign</h-></code> within the name would cause confusion because
unsigned types have no sign.
While the name <code><h- data-h=id>sign_mask</h-></code> has some precedent,
it also frequently refers to a mask where the uppermost bit is set,
i.e. a mask <em>of</em> the sign bit.
</p>
<h3 id=simd-support><a class=para href=#simd-support></a>3.3. SIMD support</h3>

<p>Following <a href="https://wg21%2elink/p2933r4">[P2933R4]</a>,
almost all functions (e.g. excluding <code><h- data-h=id>bit_cast</h-></code>) in <code><h- data-h=str>&lt;bit&gt;</h-></code>
should also have <code><h- data-h=id>std</h-><h- data-h=sym_op>::</h-><h- data-h=id>simd</h-></code> overloads.
There is no compelling reason why the proposed function should break that pattern.
</p>
<h2 id=implementation><a class=para href=#implementation></a>4. Implementation</h2>

<code-block><h- data-h=kw>namespace</h-> <h- data-h=id>std</h-> <h- data-h=sym_brac>{</h->
  <h- data-h=kw>template</h-><h- data-h=sym_op>&lt;</h-><i><h- data-h=id>signed-or-unsigned-integer</h-></i> <h- data-h=id>T</h-><h- data-h=sym_op>&gt;</h->
    <h- data-h=kw>constexpr</h-> <h- data-h=id>T</h-> <h- data-h=id>msb_to_mask</h-><h- data-h=sym_par>(</h-><h- data-h=id>T</h-> <h- data-h=id>x</h-><h- data-h=sym_par>)</h-> <h- data-h=kw>noexcept</h-> <h- data-h=sym_brac>{</h->
      <h- data-h=kw>using</h-> <h- data-h=id>S</h-> <h- data-h=sym_op>=</h-> <h- data-h=id_type>make_signed_t</h-><h- data-h=sym_op>&lt;</h-><h- data-h=id>T</h-><h- data-h=sym_op>&gt;</h-><h- data-h=sym_punc>;</h->
      <h- data-h=kw_ctrl>return</h-> <h- data-h=kw>static_cast</h-><h- data-h=sym_op>&lt;</h-><h- data-h=id>T</h-><h- data-h=sym_op>&gt;</h-><h- data-h=sym_par>(</h-><h- data-h=kw>static_cast</h-><h- data-h=sym_op>&lt;</h-><h- data-h=id>S</h-><h- data-h=sym_op>&gt;</h-><h- data-h=sym_par>(</h-><h- data-h=id>x</h-><h- data-h=sym_par>)</h-> <h- data-h=sym_op>&gt;&gt;</h-> <h- data-h=id>numeric_limits</h-><h- data-h=sym_op>&lt;</h-><h- data-h=id>S</h-><h- data-h=sym_op>&gt;</h-><h- data-h=sym_op>::</h-><h- data-h=id>digits</h-><h- data-h=sym_par>)</h-><h- data-h=sym_punc>;</h->
    <h- data-h=sym_brac>}</h->

  <h- data-h=kw>namespace</h-> <h- data-h=id>simd</h-> <h- data-h=sym_brac>{</h->
    <h- data-h=kw>template</h-><h- data-h=sym_op>&lt;</h-><i><h- data-h=id>simd-type</h-></i> <h- data-h=id>V</h-><h- data-h=sym_op>&gt;</h->
      <h- data-h=kw>constexpr</h-> <h- data-h=id>V</h-> <h- data-h=id>msb_to_mask</h-><h- data-h=sym_par>(</h-><h- data-h=kw>const</h-> <h- data-h=id>V</h-><h- data-h=sym_op>&amp;</h-> <h- data-h=id>v</h-><h- data-h=sym_par>)</h-> <h- data-h=kw>noexcept</h-> <h- data-h=sym_brac>{</h->
        <h- data-h=kw>using</h-> <h- data-h=id>S</h-> <h- data-h=sym_op>=</h-> <h- data-h=id_type>rebind_t</h-><h- data-h=sym_op>&lt;</h-><h- data-h=id_type>make_signed_t</h-><h- data-h=sym_op>&lt;</h-><h- data-h=kw>typename</h-> <h- data-h=id>V</h-><h- data-h=sym_op>::</h-><h- data-h=id>value_type</h-><h- data-h=sym_op>&gt;</h-><h- data-h=sym_punc>,</h-> <h- data-h=id>V</h-><h- data-h=sym_op>&gt;</h-><h- data-h=sym_punc>;</h->
        <h- data-h=kw_ctrl>return</h-> <h- data-h=kw>static_cast</h-><h- data-h=sym_op>&lt;</h-><h- data-h=id>T</h-><h- data-h=sym_op>&gt;</h-><h- data-h=sym_par>(</h-><h- data-h=kw>static_cast</h-><h- data-h=sym_op>&lt;</h-><h- data-h=id>S</h-><h- data-h=sym_op>&gt;</h-><h- data-h=sym_par>(</h-><h- data-h=id>v</h-><h- data-h=sym_par>)</h-> <h- data-h=sym_op>&gt;&gt;</h-> <h- data-h=id>numeric_limits</h-><h- data-h=sym_op>&lt;</h-><h- data-h=id>S</h-><h- data-h=sym_op>&gt;</h-><h- data-h=sym_op>::</h-><h- data-h=id>digits</h-><h- data-h=sym_par>)</h-><h- data-h=sym_punc>;</h->
      <h- data-h=sym_brac>}</h->
  <h- data-h=sym_brac>}</h->
<h- data-h=sym_brac>}</h-></code-block>

<note-block><p><intro-></intro-> 
The SIMD implementation is naive.
On x86_64 with SSE, an optimal implementation would be based on e.g.:
</p><code-block><h- data-h=id>_mm_cmplt_epi32</h-><h- data-h=sym_par>(</h-><h- data-h=id>v</h-><h- data-h=sym_punc>,</h-> <h- data-h=id>_mm_setzero_si128</h-><h- data-h=sym_par>(</h-><h- data-h=sym_par>)</h-><h- data-h=sym_par>)</h-></code-block>
<p>That is because comparison instructions like <code><h- data-h=id>_mm_cmplt_epi32</h-></code>
already yield bit-masks as results.
</p></note-block>

<h2 id=wording><a class=para href=#wording></a>5. Wording</h2>

<p>Bump feature-test macros in <a href=https://eel%2eis/c++draft/version%2esyn>[version.syn]</a> as follows:
</p>
<diff-block>
<code-block class=borderless><h- data-h=mac>#define __cpp_lib_bitops </h-><del><h- data-h=mac>201907L</h-></del><h- data-h=mac> </h-><ins><h- data-h=mac>20XXXXL</h-></ins><h- data-h=mac> </h-><h- data-h=cmt_dlim>//</h-><h- data-h=cmt> </h-><f-serif><h- data-h=cmt>freestanding, also in </h-><tt-><h- data-h=cmt>&lt;bit&gt;</h-></tt-></f-serif>
<h- data-h=mac>#define __cpp_lib_simd </h-><del><h- data-h=mac>202502L</h-></del><h- data-h=mac> </h-><ins><h- data-h=mac>20XXXXL</h-></ins><h- data-h=mac>   </h-><h- data-h=cmt_dlim>//</h-><h- data-h=cmt> </h-><f-serif><h- data-h=cmt>also in </h-><tt-><h- data-h=cmt>&lt;simd&gt;</h-></tt-></f-serif></code-block>
</diff-block>

<h3 id=bit><a class=para href=#bit></a>5.1. [bit]</h3>

<p>In <a href=https://eel%2eis/c++draft/bit%2esyn>[bit.syn]</a>, change the synopsis as follows:
</p>
<diff-block>
<code-block class=borderless><h- data-h=kw>namespace</h-> <h- data-h=id>std</h-> <h- data-h=sym_brac>{</h->
  […]

  <h- data-h=cmt_dlim>//</h-><h- data-h=cmt> </h-><f-serif><h- data-h=cmt>[bit.count], counting</h-></f-serif>
  <h- data-h=kw>template</h-><h- data-h=sym_op>&lt;</h-><h- data-h=kw>class</h-> <h- data-h=id>T</h-><h- data-h=sym_op>&gt;</h->
    <h- data-h=kw>constexpr</h-> <h- data-h=kw_type>int</h-> <h- data-h=id>countl_zero</h-><h- data-h=sym_par>(</h-><h- data-h=id>T</h-> <h- data-h=id>x</h-><h- data-h=sym_par>)</h-> <h- data-h=kw>noexcept</h-><h- data-h=sym_punc>;</h->
  <h- data-h=kw>template</h-><h- data-h=sym_op>&lt;</h-><h- data-h=kw>class</h-> <h- data-h=id>T</h-><h- data-h=sym_op>&gt;</h->
    <h- data-h=kw>constexpr</h-> <h- data-h=kw_type>int</h-> <h- data-h=id>countl_one</h-><h- data-h=sym_par>(</h-><h- data-h=id>T</h-> <h- data-h=id>x</h-><h- data-h=sym_par>)</h-> <h- data-h=kw>noexcept</h-><h- data-h=sym_punc>;</h->
  <h- data-h=kw>template</h-><h- data-h=sym_op>&lt;</h-><h- data-h=kw>class</h-> <h- data-h=id>T</h-><h- data-h=sym_op>&gt;</h->
    <h- data-h=kw>constexpr</h-> <h- data-h=kw_type>int</h-> <h- data-h=id>countr_zero</h-><h- data-h=sym_par>(</h-><h- data-h=id>T</h-> <h- data-h=id>x</h-><h- data-h=sym_par>)</h-> <h- data-h=kw>noexcept</h-><h- data-h=sym_punc>;</h->
  <h- data-h=kw>template</h-><h- data-h=sym_op>&lt;</h-><h- data-h=kw>class</h-> <h- data-h=id>T</h-><h- data-h=sym_op>&gt;</h->
    <h- data-h=kw>constexpr</h-> <h- data-h=kw_type>int</h-> <h- data-h=id>countr_one</h-><h- data-h=sym_par>(</h-><h- data-h=id>T</h-> <h- data-h=id>x</h-><h- data-h=sym_par>)</h-> <h- data-h=kw>noexcept</h-><h- data-h=sym_punc>;</h->
  <h- data-h=kw>template</h-><h- data-h=sym_op>&lt;</h-><h- data-h=kw>class</h-> <h- data-h=id>T</h-><h- data-h=sym_op>&gt;</h->
    <h- data-h=kw>constexpr</h-> <h- data-h=kw_type>int</h-> <h- data-h=id>popcount</h-><h- data-h=sym_par>(</h-><h- data-h=id>T</h-> <h- data-h=id>x</h-><h- data-h=sym_par>)</h-> <h- data-h=kw>noexcept</h-><h- data-h=sym_punc>;</h->

<ins>  <h- data-h=cmt_dlim>//</h-><h- data-h=cmt> </h-><f-serif><h- data-h=cmt>[bit.mask], masks</h-></f-serif>
  <h- data-h=kw>template</h-><h- data-h=sym_op>&lt;</h-><h- data-h=kw>class</h-> <h- data-h=id>T</h-><h- data-h=sym_op>&gt;</h->
    <h- data-h=kw>constexpr</h-> <h- data-h=id>T</h-> <h- data-h=id>msb_to_mask</h-><h- data-h=sym_par>(</h-><h- data-h=id>T</h-> <h- data-h=id>x</h-><h- data-h=sym_par>)</h-> <h- data-h=kw>noexcept</h-><h- data-h=sym_punc>;</h-></ins>

  […]
<h- data-h=sym_brac>}</h-></code-block>
</diff-block>

<p>In <a href=https://eel%2eis/c++draft/bit>[bit]</a>, add a new subclause immediately following <a href=https://eel%2eis/c++draft/bit%2ecount>[bit.count]</a>:
</p>
<ins-block>
<h3>Masks <span class=stable-ref>[bit.mask]</span></h3>

<code-block class=borderless><h- data-h=kw>template</h-><h- data-h=sym_op>&lt;</h-><h- data-h=kw>class</h-> <h- data-h=id>T</h-><h- data-h=sym_op>&gt;</h->
  <h- data-h=kw>constexpr</h-> <h- data-h=id>T</h-> <h- data-h=id>msb_to_mask</h-><h- data-h=sym_par>(</h-><h- data-h=id>T</h-> <h- data-h=id>x</h-><h- data-h=sym_par>)</h-> <h- data-h=kw>noexcept</h-><h- data-h=sym_punc>;</h-></code-block>

<div class=indent>
<p><i>Constraints</i>:
<code><h- data-h=id>T</h-></code> is a signed or unsigned integer type (<a href=https://eel%2eis/c++draft/basic%2efundamental>[basic.fundamental]</a>).
</p>
<p><i>Effects</i>:
Equivalent to:
</p><div class=indent>
<code-block class=borderless><h- data-h=kw>using</h-> <h- data-h=id>S</h-> <h- data-h=sym_op>=</h-> <h- data-h=id_type>make_signed_t</h-><h- data-h=sym_op>&lt;</h-><h- data-h=id>T</h-><h- data-h=sym_op>&gt;</h-><h- data-h=sym_punc>;</h->
<h- data-h=kw_ctrl>return</h-> <h- data-h=kw>static_cast</h-><h- data-h=sym_op>&lt;</h-><h- data-h=id>T</h-><h- data-h=sym_op>&gt;</h-><h- data-h=sym_par>(</h-><h- data-h=kw>static_cast</h-><h- data-h=sym_op>&lt;</h-><h- data-h=id>S</h-><h- data-h=sym_op>&gt;</h-><h- data-h=sym_par>(</h-><h- data-h=id>x</h-><h- data-h=sym_par>)</h-> <h- data-h=sym_op>&gt;&gt;</h-> <h- data-h=id>numeric_limits</h-><h- data-h=sym_op>&lt;</h-><h- data-h=id>S</h-><h- data-h=sym_op>&gt;</h-><h- data-h=sym_op>::</h-><h- data-h=id>digits</h-><h- data-h=sym_par>)</h-><h- data-h=sym_punc>;</h-></code-block>
</div>
</div>
</ins-block>

<h3 id=simd><a class=para href=#simd></a>5.2. [simd]</h3>

<p>In <a href=https://eel%2eis/c++draft/simd%2esyn>[simd.syn]</a>, change the synopsis as follows:
</p>
<diff-block>
<code-block class=borderless>[…]

<h- data-h=cmt_dlim>//</h-><h- data-h=cmt> </h-><f-serif><h- data-h=cmt>[simd.bit], Bit manipulation</h-></f-serif>
<h- data-h=kw>template</h-><h- data-h=sym_op>&lt;</h-><i><h- data-h=id>simd-type</h-></i> <h- data-h=id>V</h-><h- data-h=sym_op>&gt;</h-> <h- data-h=kw>constexpr</h-> <h- data-h=id>V</h-> <h- data-h=id>byteswap</h-><h- data-h=sym_par>(</h-><h- data-h=kw>const</h-> <h- data-h=id>V</h-><h- data-h=sym_op>&amp;</h-> <h- data-h=id>v</h-><h- data-h=sym_par>)</h-> <h- data-h=kw>noexcept</h-><h- data-h=sym_punc>;</h->
<h- data-h=kw>template</h-><h- data-h=sym_op>&lt;</h-><i><h- data-h=id>simd-type</h-></i> <h- data-h=id>V</h-><h- data-h=sym_op>&gt;</h-> <h- data-h=kw>constexpr</h-> <h- data-h=id>V</h-> <h- data-h=id>bit_ceil</h-><h- data-h=sym_par>(</h-><h- data-h=kw>const</h-> <h- data-h=id>V</h-><h- data-h=sym_op>&amp;</h-> <h- data-h=id>v</h-><h- data-h=sym_par>)</h-> <h- data-h=kw>noexcept</h-><h- data-h=sym_punc>;</h->
<h- data-h=kw>template</h-><h- data-h=sym_op>&lt;</h-><i><h- data-h=id>simd-type</h-></i> <h- data-h=id>V</h-><h- data-h=sym_op>&gt;</h-> <h- data-h=kw>constexpr</h-> <h- data-h=id>V</h-> <h- data-h=id>bit_floor</h-><h- data-h=sym_par>(</h-><h- data-h=kw>const</h-> <h- data-h=id>V</h-><h- data-h=sym_op>&amp;</h-> <h- data-h=id>v</h-><h- data-h=sym_par>)</h-> <h- data-h=kw>noexcept</h-><h- data-h=sym_punc>;</h->
<ins><h- data-h=kw>template</h-><h- data-h=sym_op>&lt;</h-><i><h- data-h=id>simd-type</h-></i> <h- data-h=id>V</h-><h- data-h=sym_op>&gt;</h-> <h- data-h=kw>constexpr</h-> <h- data-h=id>V</h-> <h- data-h=id>msb_to_mask</h-><h- data-h=sym_par>(</h-><h- data-h=kw>const</h-> <h- data-h=id>V</h-><h- data-h=sym_op>&amp;</h-> <h- data-h=id>v</h-><h- data-h=sym_par>)</h-> <h- data-h=kw>noexcept</h-><h- data-h=sym_punc>;</h-></ins>

[…]

<h- data-h=cmt_dlim>//</h-><h- data-h=cmt> </h-><f-serif><h- data-h=cmt>[simd.bit], Bit manipulation</h-></f-serif>
<h- data-h=kw>using</h-> <h- data-h=id>simd</h-><h- data-h=sym_op>::</h-><h- data-h=id>byteswap</h-><h- data-h=sym_punc>;</h->
<h- data-h=kw>using</h-> <h- data-h=id>simd</h-><h- data-h=sym_op>::</h-><h- data-h=id>bit_ceil</h-><h- data-h=sym_punc>;</h->
<h- data-h=kw>using</h-> <h- data-h=id>simd</h-><h- data-h=sym_op>::</h-><h- data-h=id>bit_floor</h-><h- data-h=sym_punc>;</h->
<ins><h- data-h=kw>using</h-> <h- data-h=id>simd</h-><h- data-h=sym_op>::</h-><h- data-h=id>msb_to_mask</h-><h- data-h=sym_punc>;</h-></ins>
<h- data-h=kw>using</h-> <h- data-h=id>simd</h-><h- data-h=sym_op>::</h-><h- data-h=id>has_single_bit</h-><h- data-h=sym_punc>;</h->
<h- data-h=kw>using</h-> <h- data-h=id>simd</h-><h- data-h=sym_op>::</h-><h- data-h=id>rotl</h-><h- data-h=sym_punc>;</h->
<h- data-h=kw>using</h-> <h- data-h=id>simd</h-><h- data-h=sym_op>::</h-><h- data-h=id>rotr</h-><h- data-h=sym_punc>;</h->
<h- data-h=kw>using</h-> <h- data-h=id>simd</h-><h- data-h=sym_op>::</h-><h- data-h=id>bit_width</h-><h- data-h=sym_punc>;</h->
<h- data-h=kw>using</h-> <h- data-h=id>simd</h-><h- data-h=sym_op>::</h-><h- data-h=id>countl_zero</h-><h- data-h=sym_punc>;</h->
<h- data-h=kw>using</h-> <h- data-h=id>simd</h-><h- data-h=sym_op>::</h-><h- data-h=id>countl_one</h-><h- data-h=sym_punc>;</h->
<h- data-h=kw>using</h-> <h- data-h=id>simd</h-><h- data-h=sym_op>::</h-><h- data-h=id>countr_zero</h-><h- data-h=sym_punc>;</h->
<h- data-h=kw>using</h-> <h- data-h=id>simd</h-><h- data-h=sym_op>::</h-><h- data-h=id>countr_one</h-><h- data-h=sym_punc>;</h->
<h- data-h=kw>using</h-> <h- data-h=id>simd</h-><h- data-h=sym_op>::</h-><h- data-h=id>popcount</h-><h- data-h=sym_punc>;</h->

[…]</code-block>
</diff-block>

<p>In <a href=https://eel%2eis/c++draft/simd%2ebit>[simd.bit]</a>, following the declaration of <code><h- data-h=id>bit_floor</h-></code>,
insert a new declaration as follows:
</p>
<ins-block>
<code-block class=borderless><h- data-h=kw>template</h-><h- data-h=sym_op>&lt;</h-><i><h- data-h=id>simd-type</h-></i> <h- data-h=id>V</h-><h- data-h=sym_op>&gt;</h-> <h- data-h=kw>constexpr</h-> <h- data-h=id>V</h-> <h- data-h=id>msb_to_mask</h-><h- data-h=sym_par>(</h-><h- data-h=kw>const</h-> <h- data-h=id>V</h-><h- data-h=sym_op>&amp;</h-> <h- data-h=id>v</h-><h- data-h=sym_par>)</h-> <h- data-h=kw>noexcept</h-><h- data-h=sym_punc>;</h-></code-block>

<div class=indent>
<p><i>Constraints</i>:
The type <code><h- data-h=id>V</h-><h- data-h=sym_op>::</h-><h- data-h=id>value_type</h-></code> is a signed or unsigned integer type (<a href=https://eel%2eis/c++draft/basic%2efundamental>[basic.fundamental]</a>).
</p>
<p><i>Returns</i>:
A <code><h- data-h=id>basic_vec</h-></code> object where the <math display=inline><msup><mi>i</mi><mtext>th</mtext></msup></math> element
is initialized to the result of <code><h- data-h=id>std</h-><h- data-h=sym_op>::</h-><h- data-h=id>msb_to_mask</h-><h- data-h=sym_par>(</h-><h- data-h=id>v</h-><h- data-h=sym_sqr>[</h-><math display=inline><mi>i</mi></math><h- data-h=sym_sqr>]</h-><h- data-h=sym_par>)</h-></code> (<a href=https://eel%2eis/c++draft/bit%2emask>[bit.mask]</a>)
for all <math display=inline><mi>i</mi></math> in the range [<code><h- data-h=num>0</h-></code>, <code><h- data-h=id>V</h-><h- data-h=sym_op>::</h-><h- data-h=id>size</h-><h- data-h=sym_par>(</h-><h- data-h=sym_par>)</h-></code>).
</p></div>
</ins-block>

<h2 id=references><a class=para href=#references></a>6. References</h2>






<div class=bib><div id=bib-item-N5008 class=bib-item>
<a href="https://wg21%2elink/N5008">[N5008]</a>
<span class=bib-author>Thomas Köppe.</span>
<span class=bib-title>Working Draft, Programming Languages — C++</span>
<span class=bib-date>2025-03-15</span>
<a href="https://www%2eopen-std%2eorg/jtc1/sc22/wg21/docs/papers/2025/n5008%2epdf" class=bib-link>https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2025/n5008.pdf</a></div><div id=bib-item-BitTwiddlingHacks class=bib-item>
<a href="https://graphics%2estanford%2eedu/~seander/bithacks%2ehtml">[BitTwiddlingHacks]</a>
<span class=bib-author>Sean Eron Anderson.</span>
<span class=bib-title>Bit Twiddling Hacks</span>
<a href="https://graphics%2estanford%2eedu/~seander/bithacks%2ehtml" class=bib-link>https://graphics.stanford.edu/~seander/bithacks.html</a></div><div id=bib-item-GitHubCodeSearch class=bib-item>
<a href="https://github%2ecom/search?q=-is%253Afork+language%253AC%252B%252B++++%2522sign_mask%2528%2522&type=code">[GitHubCodeSearch]</a>
<span class=bib-title>GitHub code search for C++ uses of a "sign_mask" function</span>
<a href="https://github%2ecom/search?q=-is%253Afork+language%253AC%252B%252B++++%2522sign_mask%2528%2522&type=code" class=bib-link>https://github.com/search?q=-is%3Afork+language%3AC%2B%2B++++%22sign_mask%28%22&amp;type=code</a></div><div id=bib-item-P2933R4 class=bib-item>
<a href="https://wg21%2elink/p2933r4">[P2933R4]</a>
<span class=bib-author>Daniel Towner, Ruslan Arutyunyan.</span>
<span class=bib-title>Extend &lt;bit&gt; header function with overloads for std::simd</span>
<span class=bib-date>2025-02-13</span>
<a href="https://www%2eopen-std%2eorg/jtc1/sc22/wg21/docs/papers/2025/p2933r4%2ehtml" class=bib-link>https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2025/p2933r4.html</a></div></div>
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