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<!DOCTYPE html><html lang=en><head>
<meta content="text/html; charset=utf-8" http-equiv=Content-Type>
<title>CSS Syntax Module Level 3</title>
<link href=../default.css rel=stylesheet type=text/css>
<link href=../csslogo.ico rel="shortcut icon" type=image/x-icon>
<link href=https://www.w3.org/StyleSheets/TR/W3C-ED rel=stylesheet type=text/css>
</head>
<body class=h-entry>
<div class=head>
<p data-fill-with=logo><a class=logo href=http://www.w3.org/>
<img alt=W3C height=48 src=http://www.w3.org/Icons/w3c_home width=72>
</a></p>
<h1 class="p-name no-ref" id=title>CSS Syntax Module Level 3</h1>
<h2 class="no-num no-toc no-ref" id=subtitle>Editor's Draft,
<span class=dt-updated><span class=value-title title=20130701>1 July 2013</span></span></h2>
<div data-fill-with=spec-metadata><dl><dt>This version:<dd><a class=u-url href=http://dev.w3.org/csswg/css-syntax>http://dev.w3.org/csswg/css-syntax</a><dt>Editor's Draft:<dd><a href=http://dev.w3.org/csswg/css-syntax>http://dev.w3.org/csswg/css-syntax</a>
<dt>Feedback:</dt>
<dd><a href="mailto:www-style@w3.org?subject=%5Bcss-syntax%5D%20feedback">www-style@w3.org</a>
with subject line
“<kbd>[css-syntax] <var>… message topic …</var></kbd>”
(<a href=http://lists.w3.org/Archives/Public/www-style/ rel=discussion>archives</a>)<dt>Test Suite<dd>None Yet<dt>Editors:
<dd class="p-author h-card vcard"><a class="p-name fn u-url url" href=http://xanthir.com/contact/>Tab Atkins Jr.</a> (<span class="p-org org">Google</span>)<dd class="p-author h-card vcard"><a class="p-name fn u-url url" href=http://exyr.org/about/>Simon Sapin</a> (<span class="p-org org">Mozilla</span>)</dl></div>
<div data-fill-with=warning></div>
<p class=copyright data-fill-with=copyright><a href=http://www.w3.org/Consortium/Legal/ipr-notice#Copyright>Copyright</a> © 2013 <a href=http://www.w3.org/><abbr title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> (<a href=http://www.csail.mit.edu/><abbr title="Massachusetts Institute of Technology">MIT</abbr></a>, <a href=http://www.ercim.eu/><abbr title="European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href=http://www.keio.ac.jp/>Keio</a>, <a href=http://ev.buaa.edu.cn/>Beihang</a>), All Rights Reserved. W3C <a href=http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer>liability</a>, <a href=http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks>trademark</a> and <a href=http://www.w3.org/Consortium/Legal/copyright-documents>document use</a> rules apply.</p>
<hr title="Separator for header">
</div>
<h2 class="no-num no-toc no-ref" id=abstract>Abstract</h2>
<p class=p-summary data-fill-with=abstract>This module describes, in general terms, the basic structure and syntax of CSS stylesheets. It defines, in detail, the syntax and parsing of CSS - how to turn a stream of bytes into a meaningful stylesheet.
<a href=http://www.w3.org/TR/CSS/>CSS</a> is a language for describing the rendering of structured documents
(such as HTML and XML)
on screen, on paper, in speech, etc.</p>
<h2 class="no-num no-toc no-ref" id=status>Status of this document</h2>
<div data-fill-with=status><p>
This is a public copy of the editors' draft.
It is provided for discussion only and may change at any moment.
Its publication here does not imply endorsement of its contents by W3C.
Don't cite this document other than as work in progress.
<p>
The (<a href=http://lists.w3.org/Archives/Public/www-style/>archived</a>) public mailing list
<a href="mailto:www-style@w3.org?Subject=%5Bcss-syntax%5D%20PUT%20SUBJECT%20HERE">www-style@w3.org</a>
(see <a href=http://www.w3.org/Mail/Request>instructions</a>)
is preferred for discussion of this specification.
When sending e-mail,
please put the text “css-syntax” in the subject,
preferably like this:
“[css-syntax] <em>…summary of comment…</em>”
<p>
This document was produced by the <a href=/Style/CSS/members>CSS Working Group</a>
(part of the <a href=/Style/>Style Activity</a>).
<p>
This document was produced by a group operating under
the <a href=/Consortium/Patent-Policy-20040205/>5 February 2004 W3C Patent Policy</a>.
W3C maintains a <a href=/2004/01/pp-impl/32061/status rel=disclosure>public list of any patent disclosures</a>
made in connection with the deliverables of the group;
that page also includes instructions for disclosing a patent.
An individual who has actual knowledge of a patent which the individual believes contains <a href=/Consortium/Patent-Policy-20040205/#def-essential>Essential Claim(s)</a>
must disclose the information in accordance with <a href=/Consortium/Patent-Policy-20040205/#sec-Disclosure>section 6 of the W3C Patent Policy</a>.</div>
<div data-fill-with=at-risk></div>
<h2 class="no-num no-toc no-ref" id=contents>Table of contents</h2>
<div data-fill-with=table-of-contents><ul class=toc><li><a href=#intro><span class=secno>1 </span>
Introduction</a><ul class=toc><li><a href=#placement><span class=secno>1.1 </span>
Module interactions</a></ul><li><a href=#syntax-description><span class=secno>2 </span>
Description of CSS's Syntax</a><ul class=toc><li><a href=#error-handling><span class=secno>2.1 </span>
Error Handling</a></ul><li><a href=#tokenizing-and-parsing-css><span class=secno>3 </span>
Tokenizing and Parsing CSS</a><ul class=toc><li><a href=#overview-of-the-parsing-model><span class=secno>3.1 </span>
Overview of the Parsing Model</a><li><a href=#the-input-byte-stream><span class=secno>3.2 </span>
The input byte stream</a><li><a href=#preprocessing-the-input-stream><span class=secno>3.3 </span>
Preprocessing the input stream</a></ul><li><a href=#tokenization><span class=secno>4 </span>
Tokenization</a><ul class=toc><li><a href=#token-diagrams><span class=secno>4.1 </span>
Token Railroad Diagrams</a><li><a href=#definitions><span class=secno>4.2 </span>
Definitions</a><li><a href=#tokenizer-algorithms><span class=secno>4.3 </span>
Tokenizer Algorithms</a><ul class=toc><li><a href=#consume-a-token><span class=secno>4.3.1 </span>
Consume a token</a><li><a href=#consume-a-numeric-token><span class=secno>4.3.2 </span>
Consume a numeric token</a><li><a href=#consume-an-ident-like-token><span class=secno>4.3.3 </span>
Consume an ident-like token</a><li><a href=#consume-a-string-token><span class=secno>4.3.4 </span>
Consume a string token</a><li><a href=#consume-a-url-token><span class=secno>4.3.5 </span>
Consume a url token</a><li><a href=#consume-a-unicode-range-token><span class=secno>4.3.6 </span>
Consume a unicode-range token</a><li><a href=#consume-an-escaped-character><span class=secno>4.3.7 </span>
Consume an escaped character</a><li><a href=#check-if-two-characters-are-a-valid-escape><span class=secno>4.3.8 </span>
Check if two characters are a valid escape</a><li><a href=#check-if-three-characters-would-start-an-identifier><span class=secno>4.3.9 </span>
Check if three characters would start an identifier</a><li><a href=#check-if-three-characters-would-start-a-number><span class=secno>4.3.10 </span>
Check if three characters would start a number</a><li><a href=#consume-a-name><span class=secno>4.3.11 </span>
Consume a name</a><li><a href=#consume-a-number><span class=secno>4.3.12 </span>
Consume a number</a><li><a href=#convert-a-string-to-a-number><span class=secno>4.3.13 </span>
Convert a string to a number</a><li><a href=#consume-the-remnants-of-a-bad-url><span class=secno>4.3.14 </span>
Consume the remnants of a bad url</a><li><a href=#set-the-unicode-ranges-range><span class=secno>4.3.15 </span>
Set the 〈unicode-range〉’s range</a></ul></ul><li><a href=#parsing><span class=secno>5 </span>
Parsing</a><ul class=toc><li><a href=#parser-diagrams><span class=secno>5.1 </span>
Parser Railroad Diagrams</a><li><a href=#definitions0><span class=secno>5.2 </span>
Definitions</a><li><a href=#parser-entry-points><span class=secno>5.3 </span>
Parser Entry Points</a><ul class=toc><li><a href=#parse-a-stylesheet><span class=secno>5.3.1 </span>
Parse a stylesheet</a><li><a href=#parse-a-list-of-rules><span class=secno>5.3.2 </span>
Parse a list of rules</a><li><a href=#parse-a-rule><span class=secno>5.3.3 </span>
Parse a rule</a><li><a href=#parse-a-declaration><span class=secno>5.3.4 </span>
Parse a declaration</a><li><a href=#parse-a-list-of-declarations><span class=secno>5.3.5 </span>
Parse a list of declarations</a><li><a href=#parse-a-component-value><span class=secno>5.3.6 </span>
Parse a component value</a><li><a href=#parse-a-list-of-component-values><span class=secno>5.3.7 </span>
Parse a list of component values</a></ul><li><a href=#parser-algorithms><span class=secno>5.4 </span>
Parser Algorithms</a><ul class=toc><li><a href=#consume-a-list-of-rules><span class=secno>5.4.1 </span>
Consume a list of rules</a><li><a href=#consume-an-at-rule><span class=secno>5.4.2 </span>
Consume an at-rule</a><li><a href=#consume-a-qualified-rule><span class=secno>5.4.3 </span>
Consume a qualified rule</a><li><a href=#consume-a-list-of-declarations><span class=secno>5.4.4 </span>
Consume a list of declarations</a><li><a href=#consume-a-declaration><span class=secno>5.4.5 </span>
Consume a declaration</a><li><a href=#consume-a-component-value><span class=secno>5.4.6 </span>
Consume a component value</a><li><a href=#consume-a-simple-block><span class=secno>5.4.7 </span>
Consume a simple block</a><li><a href=#consume-a-function><span class=secno>5.4.8 </span>
Consume a function</a></ul></ul><li><a href=#anb><span class=secno>6 </span>
The <var>An+B</var> microsyntax</a><ul class=toc><li><a href=#anb-syntax><span class=secno>6.1 </span>
Informal Syntax Description</a><li><a href=#the-anb-type><span class=secno>6.2 </span>
The <code><an+b></code> type</a></ul><li><a href=#rule-defs><span class=secno>7 </span>
Defining Grammars for Rules and Other Values</a><ul class=toc><li><a href=#declaration-rule-list><span class=secno>7.1 </span>
Defining Block Contents: the <var><declaration-list></var>, <var><rule-list></var>, and <var><stylesheet></var> productions</a></ul><li><a href=#serialization><span class=secno>8 </span>Serialization</a><ul class=toc><li><a href=#serializing-anb><span class=secno>8.1 </span>
Serializing <var><an+b></var></a></ul><li><a href=#changes><span class=secno>9 </span>Changes from CSS 2.1 and Selectors Level 3</a><li><a href=#acknowledgments>
Acknowledgments</a><li><a href=#conformance>
Conformance</a><ul class=toc><li><a href=#conventions>
Document conventions</a><li><a href=#conformance-classes>
Conformance classes</a><li><a href=#partial>
Partial implementations</a><li><a href=#experimental>
Experimental implementations</a><li><a href=#testing>
Non-experimental implementations</a></ul><li><a href=#references>
References</a><ul class=toc><li><a href=#normative>
Normative References</a><li><a href=#informative>
Informative References</a></ul><li><a href=#index>
Index</a><li><a href=#property-index>
Property index</a></ul></div>
<link href=railroad-diagrams.css rel=stylesheet type=text/css>
<h2 data-level=1 id=intro><span class=secno>1 </span>
Introduction</h2>
<p> <em>This section is not normative.</em>
<p> This module defines the abstract syntax and parsing of CSS stylesheets
and other things which use CSS syntax
(such as the HTML <code>style</code> attribute).
<p> It defines algorithms for converting a stream of codepoints
(in other words, text)
into a stream of CSS tokens,
and then further into CSS objects
such as stylesheets, rules, and declarations.
<h3 data-level=1.1 id=placement><span class=secno>1.1 </span>
Module interactions</h3>
<p> This module defines the syntax and parsing of CSS stylesheets.
It supersedes the lexical scanner and grammar defined in CSS 2.1.
<h2 data-level=2 id=syntax-description><span class=secno>2 </span>
Description of CSS's Syntax</h2>
<p> <em>This section is not normative.</em>
<p> A CSS document is a series of <a data-autolink=link href=#qualified-rule>qualified rules</a>,
which are usually style rules that apply CSS properties to elements,
and <a data-autolink=link href=#at-rule>at-rules</a>,
which define special processing rules or values for the CSS document.
<p> A qualified rule starts with a prelude
then has a {}-wrapped block containing a sequence of declarations.
The meaning of the prelude varies based on the context that the rule appears in -
for style rules, it's a selector which specifies what elements the declarations will apply to.
Each declaration has a name,
followed by a colon and the declaration value.
Declarations are separated by semicolons.
<div class=example>
<p> A typical rule might look something like this:
<pre> p > a {
color: blue;
text-decoration: underline;
}
</pre>
<p> In the above rule, "<code>p > a</code>" is the selector,
which, if the source document is HTML,
selects any <code><a></code> elements that are children of a <code><p></code> element.
<p> "<code>color: blue;</code>" is a declaration specifying that,
for the elements that match the selector,
their <a class=property data-autolink=property title=color>color</a> property should have the value <span class=css data-autolink=maybe>blue</span>.
Similiarly, their <a class=property data-autolink=property title=text-decoration>text-decoration</a> property should have the value <span class=css data-autolink=maybe>underline</span>.
</div>
<p> At-rules are all different, but they have a basic structure in common.
They start with an "@" character followed by their name.
Some <a data-autolink=link href=#at-rule>at-rules</a> are simple statements,
with their name followed by more CSS values to specify their behavior,
and finally ended by a semicolon.
Others are blocks;
they can have CSS values following their name,
but they end with a {}-wrapped block,
similar to a <a data-autolink=link href=#qualified-rule>qualified rule</a>.
Even the contents of these blocks are specific to the given <a data-autolink=link href=#at-rule>at-rule</a>:
sometimes they contain a sequence of declarations, like a <a data-autolink=link href=#qualified-rule>qualified rule</a>;
other times, they may contain additional blocks, or at-rules, or other structures altogether.
<div class=example>
<p> Here are several examples of <a data-autolink=link href=#at-rule>at-rules</a> that illustrate the varied syntax they may contain.
<pre>@import "my-styles.css";</pre>
<p> The <span class=css data-autolink=maybe>@import</span> <a data-autolink=link href=#at-rule>at-rule</a> is a simple statement.
After its name, it takes a single string or <span class=css data-autolink=maybe>url()</span> function to indicate the stylesheet that it should import.
<pre> @page :left {
margin-left: 4cm;
margin-right: 3cm;
}
</pre>
<p> The <span class=css data-autolink=maybe>@page</span> <a data-autolink=link href=#at-rule>at-rule</a> consists of an optional page selector (the <span class=css data-autolink=maybe>:left</span> pseudoclass),
followed by a block of properties that apply to the page when printed.
In this way, it's very similar to a normal style rule,
except that its properties don't apply to any "element",
but rather the page itself.
<pre> @media print {
body { font-size: 10pt }
}
</pre>
<p> The <span class=css data-autolink=maybe>@media</span> <a data-autolink=link href=#at-rule>at-rule</a> begins with a media type
and a list of optional media queries.
Its block contains entire rules,
which are only applied when the <span class=css data-autolink=maybe>@media</span>s conditions are fulfilled.
</div>
<p> Property names and <a data-autolink=link href=#at-rule>at-rule</a> names are always <b>identifiers</b>,
which have to start with a letter or a hyphen followed by a letter,
and then can contain letters, numbers, hyphens, or underscores.
You can include any character at all,
even ones that CSS uses in its syntax,
by escaping it with a backslash (\) or by using a hexadecimal escape.
<p> The syntax of selectors is defined in the <a href=http://www.w3.org/TR/selectors/>Selectors spec</a>.
Similarly, the syntax of the wide variety of CSS values is defined in the <a href=http://www.w3.org/TR/css3-values/>Values & Units spec</a>.
The special syntaxes of individual <a data-autolink=link href=#at-rule>at-rules</a> can be found in the specs that define them.
<h3 data-level=2.1 id=error-handling><span class=secno>2.1 </span>
Error Handling</h3>
<p> <em>This section is not normative.</em>
<p> When errors occur in CSS,
the parser attempts to recover gracefully,
throwing away only the minimum amount of content
before returning to parsing as normal.
This is because errors aren't always mistakes -
new syntax looks like an error to an old parser,
and it's useful to be able to add new syntax to the language
without worrying about stylesheets that include it being completely broken in older UAs.
<p> The precise error-recovery behavior is detailed in the parser itself,
but it's simple enough that a short description is fairly accurate:
<p> <ul>
<li>
At the "top level" of a stylesheet,
an 〈at-keyword〉 starts an at-rule.
Anything else starts a qualified rule,
and is included in the rule's prelude.
This may produce an invalid selector,
but that's not the concern of the CSS parser —
at worst, it means the selector will match nothing.
<li>
Once an at-rule starts,
nothing is invalid from the parser's standpoint;
it's all part of the at-rule's prelude.
Encountering a semicolon 〈;〉 ends the at-rule immediately,
while encountering an opening curly-brace 〈{〉 starts the at-rule's body.
The at-rule seeks forward, matching blocks (content surrounded by (), {}, or [])
until it finds a closing curly-brace 〈}〉 that isn't matched by anything else
or inside of another block.
The contents of the at-rule are then interpreted according to the at-rule's own grammar.
<li>
Qualified rules work similarly,
except that semicolons don't end them;
instead, they are just taken in as part of the rule's prelude.
When the first {} block is found,
the contents are always interpreted as a list of declarations.
<li>
When interpreting a list of declarations,
unknown syntax at any point causes the parser to throw away whatever declaration it's currently building,
and seek forward until it finds a semicolon (or the end of the block).
It then starts fresh, trying to parse a declaration again.
<li>
If the stylesheet ends while any rule, declaration, function, string, etc. are still open,
everything is automatically closed.
This doesn't make them invalid,
though they may be incomplete
and thus thrown away when they are verified against their grammar.
</ul>
<h2 data-level=3 id=tokenizing-and-parsing-css><span class=secno>3 </span>
Tokenizing and Parsing CSS</h2>
<p> User agents must use the parsing rules described in this specification
to generate the CSSOM trees from text/css resources.
Together, these rules define what is referred to as the CSS parser.
<p> This specification defines the parsing rules for CSS documents,
whether they are syntactically correct or not.
Certain points in the parsing algorithm are said to be a <dfn id=parse-errors title="parse error">parse errors</dfn>.
The error handling for parse errors is well-defined:
user agents must either act as described below when encountering such problems,
or must abort processing at the first error that they encounter for which they do not wish to apply the rules described below.
<p> Conformance checkers must report at least one parse error condition to the user
if one or more parse error conditions exist in the document
and must not report parse error conditions
if none exist in the document.
Conformance checkers may report more than one parse error condition if more than one parse error condition exists in the document.
Conformance checkers are not required to recover from parse errors,
but if they do,
they must recover in the same way as user agents.
<h3 data-level=3.1 id=overview-of-the-parsing-model><span class=secno>3.1 </span>
Overview of the Parsing Model</h3>
<p> The input to the CSS parsing process consists of a stream of Unicode code points,
which is passed through a tokenization stage followed by a tree construction stage.
The output is a CSSStyleSheet object.
<p class=note> Note: Implementations that do not support scripting do not have to actually create a CSSOM CSSStyleSheet object,
but the CSSOM tree in such cases is still used as the model for the rest of the specification.
<h3 data-level=3.2 id=the-input-byte-stream><span class=secno>3.2 </span>
The input byte stream</h3>
<p> When parsing a stylesheet,
the stream of Unicode code points that comprises the input to the tokenization stage may be initially seen by the user agent as a stream of bytes
(typically coming over the network or from the local file system).
The bytes encode the actual characters according to a particular character encoding,
which the user agent must use to decode the bytes into characters.
<p> To decode the stream of bytes into a stream of characters,
UAs must follow these steps.
<p> The algorithms to <a href=http://encoding.spec.whatwg.org/#concept-encoding-get><dfn id=get-an-encoding>get an encoding</dfn></a>
and <a href=http://encoding.spec.whatwg.org/#decode><dfn id=decode>decode</dfn></a>
are defined in the <a href=http://encoding.spec.whatwg.org/>Encoding Standard</a>.
<p> First, determine the fallback encoding:
<ol>
<li>
If HTTP or equivalent protocol defines an encoding (e.g. via the charset parameter of the Content-Type header),
<a data-autolink=link href=#get-an-encoding>get an encoding</a> for the specified value.
If that does not return failure,
use the return value as the fallback encoding.
<li>
Otherwise, check the byte stream. If the first several bytes match the hex sequence
<pre>40 63 68 61 72 73 65 74 20 22 (not 22)* 22 3B</pre>
<p> then <a data-autolink=link href=#get-an-encoding>get an encoding</a> for the sequence of <code>(not 22)*</code> bytes,
decoded per <code>windows-1252</code>.
<p class=note> Note: Anything ASCII-compatible will do, so using <code>windows-1252</code> is fine.
<p class=note> Note: The byte sequence above,
when decoded as ASCII,
is the string "<code>@charset "…";</code>",
where the "…" is the sequence of bytes corresponding to the encoding's name.
<p> If the return value was <code>utf-16</code> or <code>utf-16be</code>,
use <code>utf-8</code> as the fallback encoding;
if it was anything else except failure,
use the return value as the fallback encoding.
<p class=note> Note: This mimics HTML <code><meta></code> behavior.
<li>
Otherwise, <a data-autolink=link href=#get-an-encoding>get an encoding</a> for the value of the <code>charset</code> attribute on the <code><link></code> element or <code><?xml-stylesheet?></code> processing instruction that caused the style sheet to be included, if any.
If that does not return failure,
use the return value as the fallback encoding.
<li>
Otherwise, if the referring style sheet or document has an encoding,
use that as the fallback encoding.
<li>
Otherwise, use <code>utf-8</code> as the fallback encoding.
</ol>
<p> Then, <a data-autolink=link href=#decode>decode</a> the byte stream using the fallback encoding.
<p class=note> Note: the <a data-autolink=link href=#decode>decode</a> algorithm lets the byte order mark (BOM) take precedence,
hence the usage of the term "fallback" above.
<p class=issue>
Anne says that steps 3/4 should be an input to this algorithm from the specs that define importing stylesheet,
to make the algorithm as a whole cleaner.
Perhaps abstract it into the concept of an "environment charset" or something?
<p class=issue>
Should we only take the charset from the referring document if it's same-origin?
<h3 data-level=3.3 id=preprocessing-the-input-stream><span class=secno>3.3 </span>
Preprocessing the input stream</h3>
<p> The input stream consists of the characters (individual unicode code-points)
pushed into it as the input byte stream is decoded.
<p> Before sending the input stream to the tokenizer,
implementations must make the following character substitutions:
<p> <ul>
<li>
Replace any U+000D CARRIAGE RETURN (CR) characters,
U+000C FORM FEED (FF) characters,
or pairs of U+000D CARRIAGE RETURN (CR) followed by U+000A LINE FEED (LF)
by a single U+000A LINE FEED (LF) character.
<li>
Replace any U+0000 NULL characters with U+FFFD REPLACEMENT CHARACTER (�).
</ul>
<h2 data-level=4 id=tokenization><span class=secno>4 </span>
Tokenization</h2>
<p> Implementations must act as if they used the following algorithms to tokenize CSS.
To transform a stream of characters into a stream of tokens,
repeatedly <a data-autolink=link href=#consume-a-token0>consume a token</a>
until an 〈EOF〉 is reached,
collecting the returned tokens into a stream.
Each call to the <a data-autolink=link href=#consume-a-token0>consume a token</a> algorithm
returns a single token,
so it can also be used "on-demand" to tokenize a stream of characters <em>during</em> parsing,
if so desired.
<p> The output of the tokenization step is a stream of zero or more of the following tokens:
〈ident〉,
〈function〉,
〈at-keyword〉,
〈hash〉,
〈string〉,
〈bad-string〉,
〈url〉,
〈bad-url〉,
〈delim〉,
〈number〉,
〈percentage〉,
〈dimension〉,
〈unicode-range〉,
〈include-match〉,
〈dash-match〉,
〈prefix-match〉,
〈suffix-match〉,
〈substring-match〉,
〈column〉,
〈whitespace〉,
〈CDO〉,
〈CDC〉,
〈colon〉,
〈semicolon〉,
〈comma〉,
〈[〉,
〈]〉,
〈(〉,
〈)〉,
〈{〉,
and 〈}〉.
<p> <ul>
<li>
〈ident〉, 〈function〉, 〈at-keyword〉, 〈hash〉, 〈string〉, and 〈url〉 tokens have a value composed of zero or more characters.
Additionally, hash tokens have a type flag set to either "id" or "unrestricted". The type flag defaults to "unrestricted" if not otherwise set.
<li>
〈delim〉 tokens have a value composed of a single character.
<li>
〈number〉, 〈percentage〉, and 〈dimension〉 tokens have a representation composed of one or more character, and a numeric value.
〈number〉 and 〈dimension〉 tokens additionally have a type flag set to either "integer" or "number". The type flag defaults to "integer" if not otherwise set.
〈dimension〉 tokens additionally have a unit composed of one or more characters.
<li>
〈unicode-range〉 tokens have a range of characters.
</ul>
<p class=note> Note: The type flag of hash tokens is used in the Selectors syntax <a data-autolink=biblio data-biblio-type=informative href=#select title=SELECT>[SELECT]</a>.
Only hash tokens with the "id" type are valid <a href=http://www.w3.org/TR/selectors/#id-selectors>ID selectors</a>.
<p class=note> Note: As a technical note,
the tokenizer defined here requires only three characters of look-ahead.
The tokens it produces are designed to allow Selectors to be parsed with one token of look-ahead,
and additional tokens may be added in the future to maintain this invariant.
<h3 data-level=4.1 id=token-diagrams><span class=secno>4.1 </span>
Token Railroad Diagrams</h3>
<p> <em>This section is non-normative.</em>
<p> This section presents an informative view of the tokenizer,
in the form of railroad diagrams.
Railroad diagrams are more compact than an explicit parser,
but often easier to read than an regular expression.
<p> These diagrams are <em>informative</em> and <em>incomplete</em>;
they describe the grammar of "correct" tokens,
but do not describe error-handling at all.
They are provided solely to make it easier to get an intuitive grasp of the syntax of each token.
<p> Diagrams with names between 〈〉 brackets represent tokens.
The rest are productions referred to by other diagrams.
<!--
The "source" of these diagrams is in ./Diagrams.src.html
The generated SVG is copied here so that JavaScript is not required
to view the spec.
-->
<dl>
<dt id=comment-diagram>comment</dt>
<dd><svg class=railroad-diagram height=81 width=497><g transform="translate(.5 .5)"><path d="M 20 31 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 41h10"></path><g><path d="M50 41h0"></path><path d="M86 41h0"></path><rect height=22 rx=10 ry=10 width=36 x=50 y=30></rect><text x=68 y=45>/*</text></g><path d="M86 41h10"></path><g><path d="M96 41h0"></path><path d="M400 41h0"></path><path d="M96 41a10 10 0 0 0 10 -10v0a10 10 0 0 1 10 -10"></path><g><path d="M116 21h264"></path></g><path d="M380 21a10 10 0 0 1 10 10v0a10 10 0 0 0 10 10"></path><path d="M96 41h20"></path><g><path d="M116 41h0"></path><path d="M380 41h0"></path><path d="M116 41h10"></path><g><path d="M126 41h0"></path><path d="M370 41h0"></path><rect height=22 width=244 x=126 y=30></rect><text x=248 y=45>anything but * followed by /</text></g><path d="M370 41h10"></path><path d="M126 41a10 10 0 0 0 -10 10v0a10 10 0 0 0 10 10"></path><g><path d="M126 61h244"></path></g><path d="M370 61a10 10 0 0 0 10 -10v0a10 10 0 0 0 -10 -10"></path></g><path d="M380 41h20"></path></g><path d="M400 41h10"></path><g><path d="M410 41h0"></path><path d="M446 41h0"></path><rect height=22 rx=10 ry=10 width=36 x=410 y=30></rect><text x=428 y=45>*/</text></g><path d="M446 41h10"></path><path d="M 456 41 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=newline-diagram>newline</dt>
<dd><svg class=railroad-diagram height=152 width=173><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><g><path d="M40 31h0"></path><path d="M132 31h0"></path><path d="M40 31h20"></path><g><path d="M60 31h8"></path><path d="M104 31h8"></path><rect height=22 rx=10 ry=10 width=36 x=68 y=20></rect><text x=86 y=35>\n</text></g><path d="M112 31h20"></path><path d="M40 31a10 10 0 0 1 10 10v10a10 10 0 0 0 10 10"></path><g><path d="M60 61h0"></path><path d="M112 61h0"></path><rect height=22 rx=10 ry=10 width=52 x=60 y=50></rect><text x=86 y=65>\r\n</text></g><path d="M112 61a10 10 0 0 0 10 -10v-10a10 10 0 0 1 10 -10"></path><path d="M40 31a10 10 0 0 1 10 10v40a10 10 0 0 0 10 10"></path><g><path d="M60 91h8"></path><path d="M104 91h8"></path><rect height=22 rx=10 ry=10 width=36 x=68 y=80></rect><text x=86 y=95>\r</text></g><path d="M112 91a10 10 0 0 0 10 -10v-40a10 10 0 0 1 10 -10"></path><path d="M40 31a10 10 0 0 1 10 10v70a10 10 0 0 0 10 10"></path><g><path d="M60 121h8"></path><path d="M104 121h8"></path><rect height=22 rx=10 ry=10 width=36 x=68 y=110></rect><text x=86 y=125>\f</text></g><path d="M112 121a10 10 0 0 0 10 -10v-70a10 10 0 0 1 10 -10"></path></g><path d="M 132 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=whitespace-character-diagram>whitespace character</dt>
<dd><svg class=railroad-diagram height=122 width=197><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><g><path d="M40 31h0"></path><path d="M156 31h0"></path><path d="M40 31h20"></path><g><path d="M60 31h8"></path><path d="M128 31h8"></path><rect height=22 rx=10 ry=10 width=60 x=68 y=20></rect><text x=98 y=35>space</text></g><path d="M136 31h20"></path><path d="M40 31a10 10 0 0 1 10 10v10a10 10 0 0 0 10 10"></path><g><path d="M60 61h20"></path><path d="M116 61h20"></path><rect height=22 rx=10 ry=10 width=36 x=80 y=50></rect><text x=98 y=65>\t</text></g><path d="M136 61a10 10 0 0 0 10 -10v-10a10 10 0 0 1 10 -10"></path><path d="M40 31a10 10 0 0 1 10 10v40a10 10 0 0 0 10 10"></path><g><path d="M60 91h0"></path><path d="M136 91h0"></path><rect height=22 width=76 x=60 y=80></rect><text x=98 y=95>newline</text></g><path d="M136 91a10 10 0 0 0 10 -10v-40a10 10 0 0 1 10 -10"></path></g><path d="M 156 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=escape-diagram>escape</dt>
<dd><svg class=railroad-diagram height=122 width=521><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 31h10"></path><g><path d="M50 31h0"></path><path d="M78 31h0"></path><rect height=22 rx=10 ry=10 width=28 x=50 y=20></rect><text x=64 y=35>\</text></g><path d="M78 31h10"></path><g><path d="M88 31h0"></path><path d="M480 31h0"></path><path d="M88 31h20"></path><g><path d="M108 31h70"></path><path d="M390 31h70"></path><rect height=22 width=212 x=178 y=20></rect><text x=284 y=35>not newline or hex digit</text></g><path d="M460 31h20"></path><path d="M88 31a10 10 0 0 1 10 10v10a10 10 0 0 0 10 10"></path><g><path d="M108 61h0"></path><path d="M460 61h0"></path><path d="M108 61h10"></path><g><path d="M118 61h0"></path><path d="M230 61h0"></path><path d="M118 61h10"></path><g><path d="M128 61h0"></path><path d="M220 61h0"></path><rect height=22 width=92 x=128 y=50></rect><text x=174 y=65>hex digit</text></g><path d="M220 61h10"></path><path d="M128 61a10 10 0 0 0 -10 10v10a10 10 0 0 0 10 10"></path><g><path d="M128 91h9.5"></path><path d="M210.5 91h9.5"></path><text class=comment x=174 y=96>1-6 times</text></g><path d="M220 91a10 10 0 0 0 10 -10v-10a10 10 0 0 0 -10 -10"></path></g><path d="M230 61h10"></path><g><path d="M240 61h0"></path><path d="M460 61h0"></path><path d="M240 61h20"></path><g><path d="M260 61h180"></path></g><path d="M440 61h20"></path><path d="M240 61a10 10 0 0 1 10 10v0a10 10 0 0 0 10 10"></path><g><path d="M260 81h0"></path><path d="M440 81h0"></path><rect height=22 width=180 x=260 y=70></rect><text x=350 y=85>whitespace character</text></g><path d="M440 81a10 10 0 0 0 10 -10v0a10 10 0 0 1 10 -10"></path></g></g><path d="M460 61a10 10 0 0 0 10 -10v-10a10 10 0 0 1 10 -10"></path></g><path d="M 480 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈whitespace〉-diagram>〈whitespace〉</dt>
<dd><svg class=railroad-diagram height=71 width=301><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 31h10"></path><g><path d="M50 31h0"></path><path d="M250 31h0"></path><path d="M50 31h10"></path><g><path d="M60 31h0"></path><path d="M240 31h0"></path><rect height=22 width=180 x=60 y=20></rect><text x=150 y=35>whitespace character</text></g><path d="M240 31h10"></path><path d="M60 31a10 10 0 0 0 -10 10v0a10 10 0 0 0 10 10"></path><g><path d="M60 51h180"></path></g><path d="M240 51a10 10 0 0 0 10 -10v0a10 10 0 0 0 -10 -10"></path></g><path d="M250 31h10"></path><path d="M 260 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈ident〉-diagram>〈ident〉</dt>
<dd><svg class=railroad-diagram height=110 width=729><g transform="translate(.5 .5)"><path d="M 20 31 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><g><path d="M40 41h0"></path><path d="M108 41h0"></path><path d="M40 41h20"></path><g><path d="M60 41h28"></path></g><path d="M88 41h20"></path><path d="M40 41a10 10 0 0 1 10 10v0a10 10 0 0 0 10 10"></path><g><path d="M60 61h0"></path><path d="M88 61h0"></path><rect height=22 rx=10 ry=10 width=28 x=60 y=50></rect><text x=74 y=65>-</text></g><path d="M88 61a10 10 0 0 0 10 -10v0a10 10 0 0 1 10 -10"></path></g><g><path d="M108 41h0"></path><path d="M344 41h0"></path><path d="M108 41h20"></path><g><path d="M128 41h0"></path><path d="M324 41h0"></path><rect height=22 width=196 x=128 y=30></rect><text x=226 y=45>a-z A-Z _ or non-ASCII</text></g><path d="M324 41h20"></path><path d="M108 41a10 10 0 0 1 10 10v10a10 10 0 0 0 10 10"></path><g><path d="M128 71h64"></path><path d="M260 71h64"></path><rect height=22 width=68 x=192 y=60></rect><text x=226 y=75>escape</text></g><path d="M324 71a10 10 0 0 0 10 -10v-10a10 10 0 0 1 10 -10"></path></g><g><path d="M344 41h0"></path><path d="M688 41h0"></path><path d="M344 41a10 10 0 0 0 10 -10v0a10 10 0 0 1 10 -10"></path><g><path d="M364 21h304"></path></g><path d="M668 21a10 10 0 0 1 10 10v0a10 10 0 0 0 10 10"></path><path d="M344 41h20"></path><g><path d="M364 41h0"></path><path d="M668 41h0"></path><path d="M364 41h10"></path><g><path d="M374 41h0"></path><path d="M658 41h0"></path><path d="M374 41h20"></path><g><path d="M394 41h0"></path><path d="M638 41h0"></path><rect height=22 width=244 x=394 y=30></rect><text x=516 y=45>a-z A-Z 0-9 _ - or non-ASCII</text></g><path d="M638 41h20"></path><path d="M374 41a10 10 0 0 1 10 10v10a10 10 0 0 0 10 10"></path><g><path d="M394 71h88"></path><path d="M550 71h88"></path><rect height=22 width=68 x=482 y=60></rect><text x=516 y=75>escape</text></g><path d="M638 71a10 10 0 0 0 10 -10v-10a10 10 0 0 1 10 -10"></path></g><path d="M658 41h10"></path><path d="M374 41a10 10 0 0 0 -10 10v29a10 10 0 0 0 10 10"></path><g><path d="M374 90h284"></path></g><path d="M658 90a10 10 0 0 0 10 -10v-29a10 10 0 0 0 -10 -10"></path></g><path d="M668 41h20"></path></g><path d="M 688 41 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈function〉-diagram>〈function〉</dt>
<dd><svg class=railroad-diagram height=62 width=225><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 31h10"></path><g><path d="M50 31h0"></path><path d="M126 31h0"></path><rect height=22 width=76 x=50 y=20></rect><text x=88 y=35>〈ident〉</text></g><path d="M126 31h10"></path><path d="M136 31h10"></path><g><path d="M146 31h0"></path><path d="M174 31h0"></path><rect height=22 rx=10 ry=10 width=28 x=146 y=20></rect><text x=160 y=35>(</text></g><path d="M174 31h10"></path><path d="M 184 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈at-keyword〉-diagram>〈at-keyword〉</dt>
<dd><svg class=railroad-diagram height=62 width=225><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 31h10"></path><g><path d="M50 31h0"></path><path d="M78 31h0"></path><rect height=22 rx=10 ry=10 width=28 x=50 y=20></rect><text x=64 y=35>@</text></g><path d="M78 31h10"></path><path d="M88 31h10"></path><g><path d="M98 31h0"></path><path d="M174 31h0"></path><rect height=22 width=76 x=98 y=20></rect><text x=136 y=35>〈ident〉</text></g><path d="M174 31h10"></path><path d="M 184 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈hash〉-diagram>〈hash〉</dt>
<dd><svg class=railroad-diagram height=100 width=453><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 31h10"></path><g><path d="M50 31h0"></path><path d="M78 31h0"></path><rect height=22 rx=10 ry=10 width=28 x=50 y=20></rect><text x=64 y=35>#</text></g><path d="M78 31h10"></path><path d="M88 31h10"></path><g><path d="M98 31h0"></path><path d="M402 31h0"></path><path d="M98 31h10"></path><g><path d="M108 31h0"></path><path d="M392 31h0"></path><path d="M108 31h20"></path><g><path d="M128 31h0"></path><path d="M372 31h0"></path><rect height=22 width=244 x=128 y=20></rect><text x=250 y=35>a-z A-Z 0-9 _ - or non-ASCII</text></g><path d="M372 31h20"></path><path d="M108 31a10 10 0 0 1 10 10v10a10 10 0 0 0 10 10"></path><g><path d="M128 61h88"></path><path d="M284 61h88"></path><rect height=22 width=68 x=216 y=50></rect><text x=250 y=65>escape</text></g><path d="M372 61a10 10 0 0 0 10 -10v-10a10 10 0 0 1 10 -10"></path></g><path d="M392 31h10"></path><path d="M108 31a10 10 0 0 0 -10 10v29a10 10 0 0 0 10 10"></path><g><path d="M108 80h284"></path></g><path d="M392 80a10 10 0 0 0 10 -10v-29a10 10 0 0 0 -10 -10"></path></g><path d="M402 31h10"></path><path d="M 412 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈string〉-diagram>〈string〉</dt>
<dd><svg class=railroad-diagram height=248 width=481><g transform="translate(.5 .5)"><path d="M 20 31 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><g><path d="M40 41h0"></path><path d="M440 41h0"></path><path d="M40 41h20"></path><g><path d="M60 41h0"></path><path d="M420 41h0"></path><path d="M60 41h10"></path><g><path d="M70 41h0"></path><path d="M98 41h0"></path><rect height=22 rx=10 ry=10 width=28 x=70 y=30></rect><text x=84 y=45>"</text></g><path d="M98 41h10"></path><g><path d="M108 41h0"></path><path d="M372 41h0"></path><path d="M108 41a10 10 0 0 0 10 -10v0a10 10 0 0 1 10 -10"></path><g><path d="M128 21h224"></path></g><path d="M352 21a10 10 0 0 1 10 10v0a10 10 0 0 0 10 10"></path><path d="M108 41h20"></path><g><path d="M128 41h0"></path><path d="M352 41h0"></path><path d="M128 41h10"></path><g><path d="M138 41h0"></path><path d="M342 41h0"></path><path d="M138 41h20"></path><g><path d="M158 41h0"></path><path d="M322 41h0"></path><rect height=22 width=164 x=158 y=30></rect><text x=240 y=45>not " \ or newline</text></g><path d="M322 41h20"></path><path d="M138 41a10 10 0 0 1 10 10v10a10 10 0 0 0 10 10"></path><g><path d="M158 71h48"></path><path d="M274 71h48"></path><rect height=22 width=68 x=206 y=60></rect><text x=240 y=75>escape</text></g><path d="M322 71a10 10 0 0 0 10 -10v-10a10 10 0 0 1 10 -10"></path><path d="M138 41a10 10 0 0 1 10 10v40a10 10 0 0 0 10 10"></path><g><path d="M158 101h10"></path><path d="M312 101h10"></path><path d="M168 101h10"></path><g><path d="M178 101h0"></path><path d="M206 101h0"></path><rect height=22 rx=10 ry=10 width=28 x=178 y=90></rect><text x=192 y=105>\</text></g><path d="M206 101h10"></path><path d="M216 101h10"></path><g><path d="M226 101h0"></path><path d="M302 101h0"></path><rect height=22 width=76 x=226 y=90></rect><text x=264 y=105>newline</text></g><path d="M302 101h10"></path></g><path d="M322 101a10 10 0 0 0 10 -10v-40a10 10 0 0 1 10 -10"></path></g><path d="M342 41h10"></path><path d="M138 41a10 10 0 0 0 -10 10v59a10 10 0 0 0 10 10"></path><g><path d="M138 120h204"></path></g><path d="M342 120a10 10 0 0 0 10 -10v-59a10 10 0 0 0 -10 -10"></path></g><path d="M352 41h20"></path></g><path d="M372 41h10"></path><g><path d="M382 41h0"></path><path d="M410 41h0"></path><rect height=22 rx=10 ry=10 width=28 x=382 y=30></rect><text x=396 y=45>"</text></g><path d="M410 41h10"></path></g><path d="M420 41h20"></path><path d="M40 41a10 10 0 0 1 10 10v88a10 10 0 0 0 10 10"></path><g><path d="M60 149h0"></path><path d="M420 149h0"></path><path d="M60 149h10"></path><g><path d="M70 149h0"></path><path d="M98 149h0"></path><rect height=22 rx=10 ry=10 width=28 x=70 y=138></rect><text x=84 y=153>'</text></g><path d="M98 149h10"></path><g><path d="M108 149h0"></path><path d="M372 149h0"></path><path d="M108 149a10 10 0 0 0 10 -10v0a10 10 0 0 1 10 -10"></path><g><path d="M128 129h224"></path></g><path d="M352 129a10 10 0 0 1 10 10v0a10 10 0 0 0 10 10"></path><path d="M108 149h20"></path><g><path d="M128 149h0"></path><path d="M352 149h0"></path><path d="M128 149h10"></path><g><path d="M138 149h0"></path><path d="M342 149h0"></path><path d="M138 149h20"></path><g><path d="M158 149h0"></path><path d="M322 149h0"></path><rect height=22 width=164 x=158 y=138></rect><text x=240 y=153>not ' \ or newline</text></g><path d="M322 149h20"></path><path d="M138 149a10 10 0 0 1 10 10v10a10 10 0 0 0 10 10"></path><g><path d="M158 179h48"></path><path d="M274 179h48"></path><rect height=22 width=68 x=206 y=168></rect><text x=240 y=183>escape</text></g><path d="M322 179a10 10 0 0 0 10 -10v-10a10 10 0 0 1 10 -10"></path><path d="M138 149a10 10 0 0 1 10 10v40a10 10 0 0 0 10 10"></path><g><path d="M158 209h10"></path><path d="M312 209h10"></path><path d="M168 209h10"></path><g><path d="M178 209h0"></path><path d="M206 209h0"></path><rect height=22 rx=10 ry=10 width=28 x=178 y=198></rect><text x=192 y=213>\</text></g><path d="M206 209h10"></path><path d="M216 209h10"></path><g><path d="M226 209h0"></path><path d="M302 209h0"></path><rect height=22 width=76 x=226 y=198></rect><text x=264 y=213>newline</text></g><path d="M302 209h10"></path></g><path d="M322 209a10 10 0 0 0 10 -10v-40a10 10 0 0 1 10 -10"></path></g><path d="M342 149h10"></path><path d="M138 149a10 10 0 0 0 -10 10v59a10 10 0 0 0 10 10"></path><g><path d="M138 228h204"></path></g><path d="M342 228a10 10 0 0 0 10 -10v-59a10 10 0 0 0 -10 -10"></path></g><path d="M352 149h20"></path></g><path d="M372 149h10"></path><g><path d="M382 149h0"></path><path d="M410 149h0"></path><rect height=22 rx=10 ry=10 width=28 x=382 y=138></rect><text x=396 y=153>'</text></g><path d="M410 149h10"></path></g><path d="M420 149a10 10 0 0 0 10 -10v-88a10 10 0 0 1 10 -10"></path></g><path d="M 440 41 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈url〉-diagram>〈url〉</dt>
<dd><svg class=railroad-diagram height=102 width=829><g transform="translate(.5 .5)"><path d="M 20 31 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 41h10"></path><g><path d="M50 41h0"></path><path d="M174 41h0"></path><rect height=22 width=124 x=50 y=30></rect><text x=112 y=45>〈ident "url"〉</text></g><path d="M174 41h10"></path><path d="M184 41h10"></path><g><path d="M194 41h0"></path><path d="M222 41h0"></path><rect height=22 rx=10 ry=10 width=28 x=194 y=30></rect><text x=208 y=45>(</text></g><path d="M222 41h10"></path><g><path d="M232 41h0"></path><path d="M388 41h0"></path><path d="M232 41h20"></path><g><path d="M252 41h116"></path></g><path d="M368 41h20"></path><path d="M232 41a10 10 0 0 1 10 10v0a10 10 0 0 0 10 10"></path><g><path d="M252 61h0"></path><path d="M368 61h0"></path><rect height=22 width=116 x=252 y=50></rect><text x=310 y=65>〈whitespace〉</text></g><path d="M368 61a10 10 0 0 0 10 -10v0a10 10 0 0 1 10 -10"></path></g><g><path d="M388 41h0"></path><path d="M740 41h0"></path><path d="M388 41a10 10 0 0 0 10 -10v0a10 10 0 0 1 10 -10"></path><g><path d="M408 21h312"></path></g><path d="M720 21a10 10 0 0 1 10 10v0a10 10 0 0 0 10 10"></path><path d="M388 41h20"></path><g><path d="M408 41h0"></path><path d="M720 41h0"></path><g><path d="M408 41h0"></path><path d="M564 41h0"></path><path d="M408 41h20"></path><g><path d="M428 41h0"></path><path d="M544 41h0"></path><rect height=22 width=116 x=428 y=30></rect><text x=486 y=45>url-unquoted</text></g><path d="M544 41h20"></path><path d="M408 41a10 10 0 0 1 10 10v10a10 10 0 0 0 10 10"></path><g><path d="M428 71h24"></path><path d="M520 71h24"></path><rect height=22 width=68 x=452 y=60></rect><text x=486 y=75>STRING</text></g><path d="M544 71a10 10 0 0 0 10 -10v-10a10 10 0 0 1 10 -10"></path></g><g><path d="M564 41h0"></path><path d="M720 41h0"></path><path d="M564 41h20"></path><g><path d="M584 41h116"></path></g><path d="M700 41h20"></path><path d="M564 41a10 10 0 0 1 10 10v0a10 10 0 0 0 10 10"></path><g><path d="M584 61h0"></path><path d="M700 61h0"></path><rect height=22 width=116 x=584 y=50></rect><text x=642 y=65>〈whitespace〉</text></g><path d="M700 61a10 10 0 0 0 10 -10v0a10 10 0 0 1 10 -10"></path></g></g><path d="M720 41h20"></path></g><path d="M740 41h10"></path><g><path d="M750 41h0"></path><path d="M778 41h0"></path><rect height=22 rx=10 ry=10 width=28 x=750 y=30></rect><text x=764 y=45>)</text></g><path d="M778 41h10"></path><path d="M 788 41 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=url-unquoted-diagram>url-unquoted</dt>
<dd><svg class=railroad-diagram height=100 width=509><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 31h10"></path><g><path d="M50 31h0"></path><path d="M458 31h0"></path><path d="M50 31h10"></path><g><path d="M60 31h0"></path><path d="M448 31h0"></path><path d="M60 31h20"></path><g><path d="M80 31h0"></path><path d="M428 31h0"></path><rect height=22 width=348 x=80 y=20></rect><text x=254 y=35>not " ' ( ) \ whitespace or non-printable</text></g><path d="M428 31h20"></path><path d="M60 31a10 10 0 0 1 10 10v10a10 10 0 0 0 10 10"></path><g><path d="M80 61h140"></path><path d="M288 61h140"></path><rect height=22 width=68 x=220 y=50></rect><text x=254 y=65>escape</text></g><path d="M428 61a10 10 0 0 0 10 -10v-10a10 10 0 0 1 10 -10"></path></g><path d="M448 31h10"></path><path d="M60 31a10 10 0 0 0 -10 10v29a10 10 0 0 0 10 10"></path><g><path d="M60 80h388"></path></g><path d="M448 80a10 10 0 0 0 10 -10v-29a10 10 0 0 0 -10 -10"></path></g><path d="M458 31h10"></path><path d="M 468 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈number〉-diagram>〈number〉</dt>
<dd><svg class=railroad-diagram height=179 width=713><g transform="translate(.5 .5)"><path d="M 20 50 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><g><path d="M40 60h0"></path><path d="M108 60h0"></path><path d="M40 60a10 10 0 0 0 10 -10v0a10 10 0 0 1 10 -10"></path><g><path d="M60 40h0"></path><path d="M88 40h0"></path><rect height=22 rx=10 ry=10 width=28 x=60 y=29></rect><text x=74 y=44>+</text></g><path d="M88 40a10 10 0 0 1 10 10v0a10 10 0 0 0 10 10"></path><path d="M40 60h20"></path><g><path d="M60 60h28"></path></g><path d="M88 60h20"></path><path d="M40 60a10 10 0 0 1 10 10v0a10 10 0 0 0 10 10"></path><g><path d="M60 80h0"></path><path d="M88 80h0"></path><rect height=22 rx=10 ry=10 width=28 x=60 y=69></rect><text x=74 y=84>-</text></g><path d="M88 80a10 10 0 0 0 10 -10v0a10 10 0 0 1 10 -10"></path></g><g><path d="M108 60h0"></path><path d="M396 60h0"></path><path d="M108 60h20"></path><g><path d="M128 60h0"></path><path d="M376 60h0"></path><path d="M128 60h10"></path><g><path d="M138 60h0"></path><path d="M218 60h0"></path><path d="M138 60h10"></path><g><path d="M148 60h0"></path><path d="M208 60h0"></path><rect height=22 width=60 x=148 y=49></rect><text x=178 y=64>digit</text></g><path d="M208 60h10"></path><path d="M148 60a10 10 0 0 0 -10 10v0a10 10 0 0 0 10 10"></path><g><path d="M148 80h60"></path></g><path d="M208 80a10 10 0 0 0 10 -10v0a10 10 0 0 0 -10 -10"></path></g><path d="M218 60h10"></path><path d="M228 60h10"></path><g><path d="M238 60h0"></path><path d="M266 60h0"></path><rect height=22 rx=10 ry=10 width=28 x=238 y=49></rect><text x=252 y=64>.</text></g><path d="M266 60h10"></path><path d="M276 60h10"></path><g><path d="M286 60h0"></path><path d="M366 60h0"></path><path d="M286 60h10"></path><g><path d="M296 60h0"></path><path d="M356 60h0"></path><rect height=22 width=60 x=296 y=49></rect><text x=326 y=64>digit</text></g><path d="M356 60h10"></path><path d="M296 60a10 10 0 0 0 -10 10v0a10 10 0 0 0 10 10"></path><g><path d="M296 80h60"></path></g><path d="M356 80a10 10 0 0 0 10 -10v0a10 10 0 0 0 -10 -10"></path></g><path d="M366 60h10"></path></g><path d="M376 60h20"></path><path d="M108 60a10 10 0 0 1 10 10v19a10 10 0 0 0 10 10"></path><g><path d="M128 99h84"></path><path d="M292 99h84"></path><path d="M212 99h10"></path><g><path d="M222 99h0"></path><path d="M282 99h0"></path><rect height=22 width=60 x=222 y=88></rect><text x=252 y=103>digit</text></g><path d="M282 99h10"></path><path d="M222 99a10 10 0 0 0 -10 10v0a10 10 0 0 0 10 10"></path><g><path d="M222 119h60"></path></g><path d="M282 119a10 10 0 0 0 10 -10v0a10 10 0 0 0 -10 -10"></path></g><path d="M376 99a10 10 0 0 0 10 -10v-19a10 10 0 0 1 10 -10"></path><path d="M108 60a10 10 0 0 1 10 10v58a10 10 0 0 0 10 10"></path><g><path d="M128 138h50"></path><path d="M326 138h50"></path><path d="M178 138h10"></path><g><path d="M188 138h0"></path><path d="M216 138h0"></path><rect height=22 rx=10 ry=10 width=28 x=188 y=127></rect><text x=202 y=142>.</text></g><path d="M216 138h10"></path><path d="M226 138h10"></path><g><path d="M236 138h0"></path><path d="M316 138h0"></path><path d="M236 138h10"></path><g><path d="M246 138h0"></path><path d="M306 138h0"></path><rect height=22 width=60 x=246 y=127></rect><text x=276 y=142>digit</text></g><path d="M306 138h10"></path><path d="M246 138a10 10 0 0 0 -10 10v0a10 10 0 0 0 10 10"></path><g><path d="M246 158h60"></path></g><path d="M306 158a10 10 0 0 0 10 -10v0a10 10 0 0 0 -10 -10"></path></g><path d="M316 138h10"></path></g><path d="M376 138a10 10 0 0 0 10 -10v-58a10 10 0 0 1 10 -10"></path></g><g><path d="M396 60h0"></path><path d="M672 60h0"></path><path d="M396 60h20"></path><g><path d="M416 60h236"></path></g><path d="M652 60h20"></path><path d="M396 60a10 10 0 0 1 10 10v28a10 10 0 0 0 10 10"></path><g><path d="M416 108h0"></path><path d="M652 108h0"></path><g><path d="M416 108h0"></path><path d="M484 108h0"></path><path d="M416 108h20"></path><g><path d="M436 108h0"></path><path d="M464 108h0"></path><rect height=22 rx=10 ry=10 width=28 x=436 y=97></rect><text x=450 y=112>e</text></g><path d="M464 108h20"></path><path d="M416 108a10 10 0 0 1 10 10v10a10 10 0 0 0 10 10"></path><g><path d="M436 138h0"></path><path d="M464 138h0"></path><rect height=22 rx=10 ry=10 width=28 x=436 y=127></rect><text x=450 y=142>E</text></g><path d="M464 138a10 10 0 0 0 10 -10v-10a10 10 0 0 1 10 -10"></path></g><g><path d="M484 108h0"></path><path d="M552 108h0"></path><path d="M484 108a10 10 0 0 0 10 -10v0a10 10 0 0 1 10 -10"></path><g><path d="M504 88h0"></path><path d="M532 88h0"></path><rect height=22 rx=10 ry=10 width=28 x=504 y=77></rect><text x=518 y=92>+</text></g><path d="M532 88a10 10 0 0 1 10 10v0a10 10 0 0 0 10 10"></path><path d="M484 108h20"></path><g><path d="M504 108h28"></path></g><path d="M532 108h20"></path><path d="M484 108a10 10 0 0 1 10 10v0a10 10 0 0 0 10 10"></path><g><path d="M504 128h0"></path><path d="M532 128h0"></path><rect height=22 rx=10 ry=10 width=28 x=504 y=117></rect><text x=518 y=132>-</text></g><path d="M532 128a10 10 0 0 0 10 -10v0a10 10 0 0 1 10 -10"></path></g><path d="M552 108h10"></path><g><path d="M562 108h0"></path><path d="M642 108h0"></path><path d="M562 108h10"></path><g><path d="M572 108h0"></path><path d="M632 108h0"></path><rect height=22 width=60 x=572 y=97></rect><text x=602 y=112>digit</text></g><path d="M632 108h10"></path><path d="M572 108a10 10 0 0 0 -10 10v0a10 10 0 0 0 10 10"></path><g><path d="M572 128h60"></path></g><path d="M632 128a10 10 0 0 0 10 -10v0a10 10 0 0 0 -10 -10"></path></g><path d="M642 108h10"></path></g><path d="M652 108a10 10 0 0 0 10 -10v-28a10 10 0 0 1 10 -10"></path></g><path d="M 672 60 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈dimension〉-diagram>〈dimension〉</dt>
<dd><svg class=railroad-diagram height=62 width=281><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 31h10"></path><g><path d="M50 31h0"></path><path d="M134 31h0"></path><rect height=22 width=84 x=50 y=20></rect><text x=92 y=35>〈number〉</text></g><path d="M134 31h10"></path><path d="M144 31h10"></path><g><path d="M154 31h0"></path><path d="M230 31h0"></path><rect height=22 width=76 x=154 y=20></rect><text x=192 y=35>〈ident〉</text></g><path d="M230 31h10"></path><path d="M 240 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈percentage〉-diagram>〈percentage〉</dt>
<dd><svg class=railroad-diagram height=62 width=233><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 31h10"></path><g><path d="M50 31h0"></path><path d="M134 31h0"></path><rect height=22 width=84 x=50 y=20></rect><text x=92 y=35>〈number〉</text></g><path d="M134 31h10"></path><path d="M144 31h10"></path><g><path d="M154 31h0"></path><path d="M182 31h0"></path><rect height=22 rx=10 ry=10 width=28 x=154 y=20></rect><text x=168 y=35>%</text></g><path d="M182 31h10"></path><path d="M 192 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈unicode-range〉-diagram>〈unicode-range〉</dt>
<dd><svg class=railroad-diagram height=222 width=600><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><g><path d="M40 31h0"></path><path d="M108 31h0"></path><path d="M40 31h20"></path><g><path d="M60 31h0"></path><path d="M88 31h0"></path><rect height=22 rx=10 ry=10 width=28 x=60 y=20></rect><text x=74 y=35>U</text></g><path d="M88 31h20"></path><path d="M40 31a10 10 0 0 1 10 10v10a10 10 0 0 0 10 10"></path><g><path d="M60 61h0"></path><path d="M88 61h0"></path><rect height=22 rx=10 ry=10 width=28 x=60 y=50></rect><text x=74 y=65>u</text></g><path d="M88 61a10 10 0 0 0 10 -10v-10a10 10 0 0 1 10 -10"></path></g><path d="M108 31h10"></path><g><path d="M118 31h0"></path><path d="M146 31h0"></path><rect height=22 rx=10 ry=10 width=28 x=118 y=20></rect><text x=132 y=35>+</text></g><path d="M146 31h10"></path><g><path d="M156 31h0"></path><path d="M559 31h0"></path><path d="M156 31h20"></path><g><path d="M176 31h115.5"></path><path d="M423.5 31h115.5"></path><path d="M291.5 31h10"></path><g><path d="M301.5 31h0"></path><path d="M413.5 31h0"></path><path d="M301.5 31h10"></path><g><path d="M311.5 31h0"></path><path d="M403.5 31h0"></path><rect height=22 width=92 x=311.5 y=20></rect><text x=357.5 y=35>hex digit</text></g><path d="M403.5 31h10"></path><path d="M311.5 31a10 10 0 0 0 -10 10v10a10 10 0 0 0 10 10"></path><g><path d="M311.5 61h9.5"></path><path d="M394 61h9.5"></path><text class=comment x=357.5 y=66>1-6 times</text></g><path d="M403.5 61a10 10 0 0 0 10 -10v-10a10 10 0 0 0 -10 -10"></path></g><path d="M413.5 31h10"></path></g><path d="M539 31h20"></path><path d="M156 31a10 10 0 0 1 10 10v50a10 10 0 0 0 10 10"></path><g><path d="M176 101h0"></path><path d="M539 101h0"></path><g><path d="M176 101h0"></path><path d="M328 101h0"></path><path d="M176 101a10 10 0 0 0 10 -10v0a10 10 0 0 1 10 -10"></path><g><path d="M196 81h112"></path></g><path d="M308 81a10 10 0 0 1 10 10v0a10 10 0 0 0 10 10"></path><path d="M176 101h20"></path><g><path d="M196 101h0"></path><path d="M308 101h0"></path><path d="M196 101h10"></path><g><path d="M206 101h0"></path><path d="M298 101h0"></path><rect height=22 width=92 x=206 y=90></rect><text x=252 y=105>hex digit</text></g><path d="M298 101h10"></path><path d="M206 101a10 10 0 0 0 -10 10v10a10 10 0 0 0 10 10"></path><g><path d="M206 131h9.5"></path><path d="M288.5 131h9.5"></path><text class=comment x=252 y=136>1-5 times</text></g><path d="M298 131a10 10 0 0 0 10 -10v-10a10 10 0 0 0 -10 -10"></path></g><path d="M308 101h20"></path></g><path d="M328 101h10"></path><g><path d="M338 101h0"></path><path d="M529 101h0"></path><path d="M338 101h10"></path><g><path d="M348 101h71.5"></path><path d="M447.5 101h71.5"></path><rect height=22 rx=10 ry=10 width=28 x=419.5 y=90></rect><text x=433.5 y=105>?</text></g><path d="M519 101h10"></path><path d="M348 101a10 10 0 0 0 -10 10v10a10 10 0 0 0 10 10"></path><g><path d="M348 131h0"></path><path d="M519 131h0"></path><text class=comment x=433.5 y=136>1 to (6 - digits) times</text></g><path d="M519 131a10 10 0 0 0 10 -10v-10a10 10 0 0 0 -10 -10"></path></g><path d="M529 101h10"></path></g><path d="M539 101a10 10 0 0 0 10 -10v-50a10 10 0 0 1 10 -10"></path><path d="M156 31a10 10 0 0 1 10 10v110a10 10 0 0 0 10 10"></path><g><path d="M176 161h25.5"></path><path d="M513.5 161h25.5"></path><path d="M201.5 161h10"></path><g><path d="M211.5 161h0"></path><path d="M323.5 161h0"></path><path d="M211.5 161h10"></path><g><path d="M221.5 161h0"></path><path d="M313.5 161h0"></path><rect height=22 width=92 x=221.5 y=150></rect><text x=267.5 y=165>hex digit</text></g><path d="M313.5 161h10"></path><path d="M221.5 161a10 10 0 0 0 -10 10v10a10 10 0 0 0 10 10"></path><g><path d="M221.5 191h9.5"></path><path d="M304 191h9.5"></path><text class=comment x=267.5 y=196>1-6 times</text></g><path d="M313.5 191a10 10 0 0 0 10 -10v-10a10 10 0 0 0 -10 -10"></path></g><path d="M323.5 161h10"></path><path d="M333.5 161h10"></path><g><path d="M343.5 161h0"></path><path d="M371.5 161h0"></path><rect height=22 rx=10 ry=10 width=28 x=343.5 y=150></rect><text x=357.5 y=165>-</text></g><path d="M371.5 161h10"></path><path d="M381.5 161h10"></path><g><path d="M391.5 161h0"></path><path d="M503.5 161h0"></path><path d="M391.5 161h10"></path><g><path d="M401.5 161h0"></path><path d="M493.5 161h0"></path><rect height=22 width=92 x=401.5 y=150></rect><text x=447.5 y=165>hex digit</text></g><path d="M493.5 161h10"></path><path d="M401.5 161a10 10 0 0 0 -10 10v10a10 10 0 0 0 10 10"></path><g><path d="M401.5 191h9.5"></path><path d="M484 191h9.5"></path><text class=comment x=447.5 y=196>1-6 times</text></g><path d="M493.5 191a10 10 0 0 0 10 -10v-10a10 10 0 0 0 -10 -10"></path></g><path d="M503.5 161h10"></path></g><path d="M539 161a10 10 0 0 0 10 -10v-110a10 10 0 0 1 10 -10"></path></g><path d="M 559 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈include-match〉-diagram>〈include-match〉</dt>
<dd><svg class=railroad-diagram height=62 width=137><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 31h10"></path><g><path d="M50 31h0"></path><path d="M86 31h0"></path><rect height=22 rx=10 ry=10 width=36 x=50 y=20></rect><text x=68 y=35>~=</text></g><path d="M86 31h10"></path><path d="M 96 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈dash-match〉-diagram>〈dash-match〉</dt>
<dd><svg class=railroad-diagram height=62 width=137><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 31h10"></path><g><path d="M50 31h0"></path><path d="M86 31h0"></path><rect height=22 rx=10 ry=10 width=36 x=50 y=20></rect><text x=68 y=35>|=</text></g><path d="M86 31h10"></path><path d="M 96 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈prefix-match〉-diagram>〈prefix-match〉</dt>
<dd><svg class=railroad-diagram height=62 width=137><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 31h10"></path><g><path d="M50 31h0"></path><path d="M86 31h0"></path><rect height=22 rx=10 ry=10 width=36 x=50 y=20></rect><text x=68 y=35>^=</text></g><path d="M86 31h10"></path><path d="M 96 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈suffix-match〉-diagram>〈suffix-match〉</dt>
<dd><svg class=railroad-diagram height=62 width=137><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 31h10"></path><g><path d="M50 31h0"></path><path d="M86 31h0"></path><rect height=22 rx=10 ry=10 width=36 x=50 y=20></rect><text x=68 y=35>$=</text></g><path d="M86 31h10"></path><path d="M 96 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈substring-match〉-diagram>〈substring-match〉</dt>
<dd><svg class=railroad-diagram height=62 width=137><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 31h10"></path><g><path d="M50 31h0"></path><path d="M86 31h0"></path><rect height=22 rx=10 ry=10 width=36 x=50 y=20></rect><text x=68 y=35>*=</text></g><path d="M86 31h10"></path><path d="M 96 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈column〉-diagram>〈column〉</dt>
<dd><svg class=railroad-diagram height=62 width=137><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 31h10"></path><g><path d="M50 31h0"></path><path d="M86 31h0"></path><rect height=22 rx=10 ry=10 width=36 x=50 y=20></rect><text x=68 y=35>||</text></g><path d="M86 31h10"></path><path d="M 96 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈CDO〉-diagram>〈CDO〉</dt>
<dd><svg class=railroad-diagram height=62 width=153><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 31h10"></path><g><path d="M50 31h0"></path><path d="M102 31h0"></path><rect height=22 rx=10 ry=10 width=52 x=50 y=20></rect><text x=76 y=35><!--</text></g><path d="M102 31h10"></path><path d="M 112 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
<dt id=〈CDC〉-diagram>〈CDC〉</dt>
<dd><svg class=railroad-diagram height=62 width=145><g transform="translate(.5 .5)"><path d="M 20 21 v 20 m 10 -20 v 20 m -10 -10 h 20.5"></path><path d="M40 31h10"></path><g><path d="M50 31h0"></path><path d="M94 31h0"></path><rect height=22 rx=10 ry=10 width=44 x=50 y=20></rect><text x=72 y=35>--></text></g><path d="M94 31h10"></path><path d="M 104 31 h 20 m -10 -10 v 20 m 10 -20 v 20"></path></g></svg></dd>
</dl>
<h3 data-level=4.2 id=definitions><span class=secno>4.2 </span>
Definitions</h3>
<p> This section defines several terms used during the tokenization phase.
<dl>
<dt><dfn id=next-input-character>next input character</dfn>
<dd>
The first character in the input stream that has not yet been consumed.
<dt><dfn id=current-input-character>current input character</dfn>
<dd>
The last character to have been consumed.
<dt><dfn id=reconsume-the-current-input-character>reconsume the current input character</dfn>
<dd>
Push the <a data-autolink=link href=#current-input-character>current input character</a> back onto the front of the input stream,
so that the next time you are instructed to consume the next input character,
it will instead reconsume the <a data-autolink=link href=#current-input-character>current input character</a>.
<dt><dfn id=eof-character>EOF character</dfn>
<dd>
A conceptual character representing the end of the input stream.
Whenever the input stream is empty,
the <a data-autolink=link href=#next-input-character>next input character</a> is always an EOF character.
<dt><dfn id=digit>digit</dfn>
<dd>
A character between U+0030 DIGIT ZERO (0) and U+0039 DIGIT NINE (9).
<dt><dfn id=hex-digit>hex digit</dfn>
<dd>
A <a data-autolink=link href=#digit>digit</a>,
or a character between U+0041 LATIN CAPITAL LETTER A (A) and U+0046 LATIN CAPITAL LETTER F (F),
or a character between U+0061 LATIN SMALL LETTER A (a) and U+0066 LATIN SMALL LETTER F (f).
<dt><dfn id=uppercase-letter>uppercase letter</dfn>
<dd>
A character between U+0041 LATIN CAPITAL LETTER A (A) and U+005A LATIN CAPITAL LETTER Z (Z).
<dt><dfn id=lowercase-letter>lowercase letter</dfn>
<dd>
A character between U+0061 LATIN SMALL LETTER A (a) and U+007A LATIN SMALL LETTER Z (z).
<dt><dfn id=letter>letter</dfn>
<dd>
An <a data-autolink=link href=#uppercase-letter>uppercase letter</a>
or a <a data-autolink=link href=#lowercase-letter>lowercase letter</a>.
<dt><dfn id=non-ascii-character>non-ASCII character</dfn>
<dd>
A character with a codepoint equal to or greater than U+0080 <control>.
<dt><dfn id=name-start-character>name-start character</dfn>
<dd>
A <a data-autolink=link href=#letter>letter</a>,
a <a data-autolink=link href=#non-ascii-character>non-ASCII character</a>,
or U+005F LOW LINE (_).
<dt><dfn id=name-character>name character</dfn>
<dd>
A <a data-autolink=link href=#name-start-character>name-start character</a>,
A <a data-autolink=link href=#digit>digit</a>,
or U+002D HYPHEN-MINUS (-).
<dt><dfn id=non-printable-character>non-printable character</dfn>
<dd>
A character between U+0000 NULL and U+0008 BACKSPACE,
or U+000B LINE TABULATION,
or a character between U+000E SHIFT OUT and U+001F INFORMATION SEPARATOR ONE,
or U+007F DELETE.
<dt><dfn id=newline>newline</dfn>
<dd>
U+000A LINE FEED.
<span class=note>
Note that U+000D CARRIAGE RETURN and U+000C FORM FEED are not included in this definition,
as they are converted to U+000A LINE FEED during <a href=#preprocessing-the-input-stream>preprocessing</a>.
</span>
<dt><dfn id=whitespace>whitespace</dfn>
<dd>A <a data-autolink=link href=#newline>newline</a>, U+0009 CHARACTER TABULATION, or U+0020 SPACE.
<dt><dfn id=maximum-allowed-codepoint>maximum allowed codepoint</dfn>
<dd>The greatest codepoint defined by Unicode. This is currently U+10FFFF.
</dl>
<h3 data-level=4.3 id=tokenizer-algorithms><span class=secno>4.3 </span>
Tokenizer Algorithms</h3>
<p> The algorithms defined in this section transform a stream of characters into a stream of tokens.
<h4 data-level=4.3.1 id=consume-a-token><span class=secno>4.3.1 </span>
<dfn id=consume-a-token0>Consume a token</dfn></h4>
<p> This section describes how to <a data-autolink=link href=#consume-a-token0>consume a token</a> from a stream of characters.
It will return a single token of any type.
<p> Consume the <a data-autolink=link href=#next-input-character>next input character</a>.
<dl>
<dt><a data-autolink=link href=#whitespace>whitespace</a>
<dd>
Consume as much <a data-autolink=link href=#whitespace>whitespace</a> as possible.
Return a 〈whitespace〉.
<dt>U+0022 QUOTATION MARK (")
<dd>
<a data-autolink=link href=#consume-a-string-token0>Consume a string token</a> with the ending character U+0022 QUOTATION MARK (")
and return it.
<dt>U+0023 NUMBER SIGN (#)
<dd>
If the <a data-autolink=link href=#next-input-character>next input character</a> is a <a data-autolink=link href=#name-character>name character</a>
or the <a data-autolink=link href=#next-input-character title="next input character">next two input characters</a>
<a data-autolink=link href=#check-if-two-characters-are-a-valid-escape0>are a valid escape</a>,
then:
<ol>
<li>
Create a 〈hash〉.
<li>
If the <a data-autolink=link href=#next-input-character title="next input character">next 3 input characters</a> <a data-autolink=link href=#check-if-three-characters-would-start-an-identifier0>would start an identifier</a>,
set the 〈hash〉’s type flag to "id".
<li>
<a data-autolink=link href=#consume-a-name0>Consume a name</a>,
and set the 〈hash〉’s value to the returned string.
<li>
Return the 〈hash〉.
</ol>
<p> Otherwise,
return a 〈delim〉
with its value set to the <a data-autolink=link href=#current-input-character>current input character</a>.
<dt>U+0024 DOLLAR SIGN ($)
<dd>
If the <a data-autolink=link href=#next-input-character>next input character</a> is
U+003D EQUALS SIGN (=),
consume it
and return a 〈suffix-match〉.
<p> Otherwise,
emit a 〈delim〉
with its value set to the <a data-autolink=link href=#current-input-character>current input character</a>.
<dt>U+0027 APOSTROPHE (')
<dd>
<a data-autolink=link href=#consume-a-string-token0>Consume a string token</a> with the ending character U+0027 APOSTROPHE (')
and return it.
<dt>U+0028 LEFT PARENTHESIS (()
<dd>
Return a 〈(〉.
<dt>U+0029 RIGHT PARENTHESIS ())
<dd>
Return a 〈)〉.
<dt>U+002A ASTERISK (*)
<dd>
If the <a data-autolink=link href=#next-input-character>next input character</a> is
U+003D EQUALS SIGN (=),
consume it
and return a 〈substring-match〉.
<p> Otherwise,
return a 〈delim〉
with its value set to the <a data-autolink=link href=#current-input-character>current input character</a>.
<dt>U+002B PLUS SIGN (+)
<dd>
If the input stream <a data-autolink=link href=#check-if-three-characters-would-start-a-number0>starts with a number</a>,
<a data-autolink=link href=#reconsume-the-current-input-character>reconsume the current input character</a>,
<a data-autolink=link href=#consume-a-numeric-token0>consume a numeric token</a>
and return it.
<p> Otherwise,
return a 〈delim〉
with its value set to the <a data-autolink=link href=#current-input-character>current input character</a>.
<dt>U+002C COMMA (,)
<dd>
Return a 〈comma〉.
<dt>U+002D HYPHEN-MINUS (-)
<dd>
If the input stream <a data-autolink=link href=#check-if-three-characters-would-start-a-number0>starts with a number</a>,
<a data-autolink=link href=#reconsume-the-current-input-character>reconsume the current input character</a>,
<a data-autolink=link href=#consume-a-numeric-token0>consume a numeric token</a>,
and return it.
<p> Otherwise,
if the input stream <a data-autolink=link href=#check-if-three-characters-would-start-an-identifier0>starts with an identifier</a>,
<a data-autolink=link href=#reconsume-the-current-input-character>reconsume the current input character</a>,
<a data-autolink=link href=#consume-an-ident-like-token0>consume an ident-like token</a>,
and return it.
<p> Otherwise,
if the <a data-autolink=link href=#next-input-character title="next input character">next 2 input characters</a> are
U+002D HYPHEN-MINUS
U+003E GREATER-THAN SIGN
(->),
consume them
and return a 〈CDC〉.
<p> Otherwise,
return a 〈delim〉
with its value set to the <a data-autolink=link href=#current-input-character>current input character</a>.
<dt>U+002E FULL STOP (.)
<dd>
If the input stream <a data-autolink=link href=#check-if-three-characters-would-start-a-number0>starts with a number</a>,
<a data-autolink=link href=#reconsume-the-current-input-character>reconsume the current input character</a>,
<a data-autolink=link href=#consume-a-numeric-token0>consume a numeric token</a>,
and return it.
<p> Otherwise,
return a 〈delim〉
with its value set to the <a data-autolink=link href=#current-input-character>current input character</a>.
<dt>U+002F SOLIDUS (/)
<dd>
If the <a data-autolink=link href=#next-input-character>next input character</a> is U+002A ASTERISK (*),
consume it
and all following characters up to and including
the first U+002A ASTERISK (*) followed by a U+002F SOLIDUS (/),
or up to an EOF character.
Then <a data-autolink=link href=#consume-a-token0>consume a token</a>
and return it.
<p> Otherwise,
return a 〈delim〉
with its value set to the <a data-autolink=link href=#current-input-character>current input character</a>.
<dt>U+003A COLON (:)
<dd>
Return a 〈colon〉.
<dt>U+003B SEMICOLON (;)
<dd>
Return a 〈semicolon〉.
<dt>U+003C LESS-THAN SIGN (<)
<dd>
If the <a data-autolink=link href=#next-input-character title="next input character">next 3 input characters</a> are
U+0021 EXCLAMATION MARK
U+002D HYPHEN-MINUS
U+002D HYPHEN-MINUS
(!--),
consume them
and return a 〈CDO〉.
<p> Otherwise,
return a 〈delim〉
with its value set to the <a data-autolink=link href=#current-input-character>current input character</a>.
<dt>U+0040 COMMERCIAL AT (@)
<dd>
If the <a data-autolink=link href=#next-input-character title="next input character">next 3 input characters</a>
<a data-autolink=link href=#check-if-three-characters-would-start-an-identifier0>would start an identifier</a>,
<a data-autolink=link href=#consume-a-name0>consume a name</a>,
create an 〈at-keyword〉 with its value set to the returned value,
and return it.
<p> Otherwise,
return a 〈delim〉
with its value set to the <a data-autolink=link href=#current-input-character>current input character</a>.
<dt>U+005B LEFT SQUARE BRACKET ([)
<dd>
Return a 〈[〉.
<dt>U+005C REVERSE SOLIDUS (\)
<dd>
If the input stream <a data-autolink=link href=#check-if-two-characters-are-a-valid-escape0>starts with a valid escape</a>,
<a data-autolink=link href=#reconsume-the-current-input-character>reconsume the current input character</a>,
<a data-autolink=link href=#consume-an-ident-like-token0>consume an ident-like token</a>,
and return it.
<p> Otherwise,
this is a <a data-autolink=link href=#parse-errors>parse error</a>.
Return a 〈delim〉
with its value set to the <a data-autolink=link href=#current-input-character>current input character</a>.
<dt>U+005D RIGHT SQUARE BRACKET (])
<dd>
Return a 〈]〉.
<dt>U+005E CIRCUMFLEX ACCENT (^)
<dd>
If the <a data-autolink=link href=#next-input-character>next input character</a> is
U+003D EQUALS SIGN (=),
consume it
and return a 〈prefix-match〉.
<p> Otherwise,
return a 〈delim〉
with its value set to the <a data-autolink=link href=#current-input-character>current input character</a>.
<dt>U+007B LEFT CURLY BRACKET ({)
<dd>
Return a 〈{〉.
<dt>U+007D RIGHT CURLY BRACKET (})
<dd>
Return a 〈}〉.
<dt><a data-autolink=link href=#digit>digit</a>
<dd>
<a data-autolink=link href=#consume-a-numeric-token0>Consume a numeric token</a>,
and return it.
<dt>U+0055 LATIN CAPITAL LETTER U (U)
<dt>U+0075 LATIN SMALL LETTER U (u)
<dd>
If the <a data-autolink=link href=#next-input-character title="next input character">next 2 input character</a> are
U+002B PLUS SIGN (+)
followed by a <a data-autolink=link href=#hex-digit>hex digit</a>
or U+003F QUESTION MARK (?),
consume the <a data-autolink=link href=#next-input-character>next input character</a>.
<span class=note>Note: don't consume both of them.</span>
<a data-autolink=link href=#consume-a-unicode-range-token0>Consume a unicode-range token</a>
and return it.
<p> Otherwise,
<a data-autolink=link href=#reconsume-the-current-input-character>reconsume the current input character</a>,
<a data-autolink=link href=#consume-an-ident-like-token0>consume an ident-like token</a>,
and return it.
<dt><a data-autolink=link href=#name-start-character>name-start character</a>
<dd>
<a data-autolink=link href=#reconsume-the-current-input-character>Reconsume the current input character</a>,
<a data-autolink=link href=#consume-an-ident-like-token0>consume an ident-like token</a>,
and return it.
<dt>U+007C VERTICAL LINE (|)
<dd>
If the <a data-autolink=link href=#next-input-character>next input character</a> is
U+003D EQUALS SIGN (=),
consume it
and return a 〈dash-match〉.
<p> Otherwise,
if the <a data-autolink=link href=#next-input-character>next input character</a> is
U+0073 VERTICAL LINE (|),
consume it
and return a 〈column〉.
<p> Otherwise,
return a 〈delim〉
with its value set to the <a data-autolink=link href=#current-input-character>current input character</a>.
<dt>U+007E TILDE (~)
<dd>
If the <a data-autolink=link href=#next-input-character>next input character</a> is
U+003D EQUALS SIGN (=),
consume it
and return an 〈include-match〉.
<p> Otherwise,
return a 〈delim〉
with its value set to the <a data-autolink=link href=#current-input-character>current input character</a>.
<dt>EOF
<dd>
Return an 〈EOF〉 token.
<dt>anything else
<dd>
Return a 〈delim〉
with its value set to the <a data-autolink=link href=#current-input-character>current input character</a>.
</dl>
<h4 data-level=4.3.2 id=consume-a-numeric-token><span class=secno>4.3.2 </span>
<dfn id=consume-a-numeric-token0>Consume a numeric token</dfn></h4>
<p> This section describes how to <a data-autolink=link href=#consume-a-numeric-token0>consume a numeric token</a> from a stream of characters.
It returns either a 〈number〉, 〈percentage〉, or 〈dimension〉.
<p> <a data-autolink=link href=#consume-a-number0>Consume a number</a>.
<p> If the <a data-autolink=link href=#next-input-character title="next input character">next 3 input characters</a> <a data-autolink=link href=#check-if-three-characters-would-start-an-identifier0>would start an identifier</a>,
then:
<ol>
<li>Create a 〈dimension〉 with the same representation, value, and type flag as the returned number,