28 lines
24 KiB
HTML
28 lines
24 KiB
HTML
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
||
|
|
<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"/><meta name="viewport" content="width=device-width, initial-scale=0.8"/><title>3.4 Strings (Unicode)</title><link rel="stylesheet" type="text/css" href="../scribble.css" title="default"/><link rel="stylesheet" type="text/css" href="../racket.css" title="default"/><link rel="stylesheet" type="text/css" href="icons.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-style.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../manual-racket.css" title="default"/><link rel="stylesheet" type="text/css" href="../doc-site.css" title="default"/><script type="text/javascript" src="../scribble-common.js"></script><script type="text/javascript" src="../manual-racket.js"></script><script type="text/javascript" src="../manual-racket.js"></script><script type="text/javascript" src="../doc-site.js"></script><script type="text/javascript" src="../local-redirect/local-redirect.js"></script><script type="text/javascript" src="../local-redirect/local-user-redirect.js"></script><!--[if IE 6]><style type="text/css">.SIEHidden { overflow: hidden; }</style><![endif]--></head><body id="doc-racket-lang-org"><div class="tocset"><div class="tocview"><div class="tocviewlist tocviewlisttopspace"><div class="tocviewtitle"><table cellspacing="0" cellpadding="0"><tr><td style="width: 1em;"><a href="javascript:void(0);" title="Expand/Collapse" class="tocviewtoggle" onclick="TocviewToggle(this,"tocview_0");">►</a></td><td></td><td><a href="index.html" class="tocviewlink" data-pltdoc="x">The Racket Guide</a></td></tr></table></div><div class="tocviewsublisttop" style="display: none;" id="tocview_0"><table cellspacing="0" cellpadding="0"><tr><td align="right">1 </td><td><a href="intro.html" class="tocviewlink" data-pltdoc="x">Welcome to Racket</a></td></tr><tr><td align="right">2 </td><td><a href="to-scheme.html" class="tocviewlink" data-pltdoc="x">Racket Essentials</a></td></tr><tr><td align="right">3 </td><td><a href="datatypes.html" class="tocviewselflink" data-pltdoc="x">Built-<wbr></wbr>In Datatypes</a></td></tr><tr><td align="right">4 </td><td><a href="scheme-forms.html" class="tocviewlink" data-pltdoc="x">Expressions and Definitions</a></td></tr><tr><td align="right">5 </td><td><a href="define-struct.html" class="tocviewlink" data-pltdoc="x">Programmer-<wbr></wbr>Defined Datatypes</a></td></tr><tr><td align="right">6 </td><td><a href="modules.html" class="tocviewlink" data-pltdoc="x">Modules</a></td></tr><tr><td align="right">7 </td><td><a href="contracts.html" class="tocviewlink" data-pltdoc="x">Contracts</a></td></tr><tr><td align="right">8 </td><td><a href="i_o.html" class="tocviewlink" data-pltdoc="x">Input and Output</a></td></tr><tr><td align="right">9 </td><td><a href="regexp.html" class="tocviewlink" data-pltdoc="x">Regular Expressions</a></td></tr><tr><td align="right">10 </td><td><a href="control.html" class="tocviewlink" data-pltdoc="x">Exceptions and Control</a></td></tr><tr><td align="right">11 </td><td><a href="for.html" class="tocviewlink" data-pltdoc="x">Iterations and Comprehensions</a></td></tr><tr><td align="right">12 </td><td><a href="match.html" class="tocviewlink" data-pltdoc="x">Pattern Matching</a></td></tr><tr><td align="right">13 </td><td><a href="classes.html" class="tocviewlink" data-pltdoc="x">Classes and Objects</a></td></tr><tr><td align="right">14 </td><td><a href="units.html" class="tocviewlink" data-pltdoc="x">Units</a></td></tr><tr><td align="right">15 </td><td><a href="reflection.html" class="tocviewlink" data-pltdoc="x">Reflection and Dynamic Evaluation</a></td></tr><tr><td align="right">16 </td><td><a href="macros.html" class="tocviewlink" data-pltdoc="x">Macros</a></td></tr><tr><td align="right">17 </td><td><a href="languages.html" class="tocviewlink" data-pltdoc="x">Creating Languages</a></td></tr><tr><td
|
||
|
|
<a href="characters.html" data-pltdoc="x">characters</a>. It prints using double quotes,
|
||
|
|
where double quote and backslash characters within the string are
|
||
|
|
escaped with backslashes. Other common string escapes are supported,
|
||
|
|
including <span class="RktInBG"><span class="hspace"></span><span class="RktIn">\n</span><span class="hspace"></span></span> for a linefeed, <span class="RktInBG"><span class="hspace"></span><span class="RktIn">\r</span><span class="hspace"></span></span> for a
|
||
|
|
carriage return, octal escapes using <span class="RktInBG"><span class="hspace"></span><span class="RktIn">\</span><span class="hspace"></span></span> followed by up
|
||
|
|
to three octal digits, and hexadecimal escapes with <span class="RktInBG"><span class="hspace"></span><span class="RktIn">\u</span><span class="hspace"></span></span>
|
||
|
|
(up to four digits). Unprintable characters in a string are normally
|
||
|
|
shown with <span class="RktInBG"><span class="hspace"></span><span class="RktIn">\u</span><span class="hspace"></span></span> when the string is printed.</p><blockquote class="refpara"><blockquote class="refcolumn"><blockquote class="refcontent"><p><span class="imageleft"><img src="magnify.png" alt="+" width="24" height="24"/></span><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=reader.html%23%2528part._parse-string%2529&version=8.6" class="Sq" data-pltdoc="x">Reading Strings</a> in <a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=index.html&version=8.6" class="Sq" data-pltdoc="x">The Racket Reference</a> documents the fine points of the syntax of strings.</p></blockquote></blockquote></blockquote><p>The <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Writing.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._display%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">display</a></span> procedure directly writes the characters of a
|
||
|
|
string to the current output port (see <a href="i_o.html" data-pltdoc="x">Input and Output</a>), in contrast
|
||
|
|
to the string-constant syntax used to print a string result.</p><p><div class="SIntrapara">Examples:</div><div class="SIntrapara"><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktVal">"Apple"</span></td></tr><tr><td><p><span class="RktRes">"Apple"</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktVal">"\u03BB"</span></td></tr><tr><td><p><span class="RktRes">"λ"</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Writing.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._display%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">display</a></span><span class="hspace"> </span><span class="RktVal">"Apple"</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktOut">Apple</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Writing.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._display%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">display</a></span><span class="hspace"> </span><span class="RktVal">"a \"quoted\" thing"</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktOut">a "quoted" thing</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Writing.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._display%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">display</a></span><span class="hspace"> </span><span class="RktVal">"two\nlines"</span><span class="RktPn">)</span></td></tr><tr><td><table cellspacing="0" cellpadding="0"><tr><td><p><span class="RktOut">two</span></p></td></tr><tr><td><p><span class="RktOut">lines</span></p></td></tr></table></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=Writing.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._display%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">display</a></span><span class="hspace"> </span><span class="RktVal">"\u03BB"</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktOut">λ</span></p></td></tr></table></blockquote></div></p><p>A string can be mutable or immutable; strings written directly as
|
||
|
|
expressions are immutable, but most other strings are mutable. The
|
||
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._make-string%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">make-string</a></span> procedure creates a mutable string given a length
|
||
|
|
and optional fill character. The <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string-ref%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">string-ref</a></span> procedure
|
||
|
|
accesses a character from a string (with 0-based indexing); the
|
||
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string-set%2521%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">string-set!</a></span> procedure changes a character in a mutable
|
||
|
|
string.</p><p><div class="SIntrapara">Examples:</div><div class="SIntrapara"><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string-ref%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">string-ref</a></span><span class="hspace"> </span><span class="RktVal">"Apple"</span><span class="hspace"> </span><span class="RktVal">0</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">#\A</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=define.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._define%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">s</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._make-string%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">make-string</a></span><span class="hspace"> </span><span class="RktVal">5</span><span class="hspace"> </span><span class="RktVal">#\.</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktSym">s</span></td></tr><tr><td><p><span class="RktRes">"....."</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string-set%2521%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">string-set!</a></span><span class="hspace"> </span><span class="RktSym">s</span><span class="hspace"> </span><span class="RktVal">2</span><span class="hspace"> </span><span class="RktVal">#\λ</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt">> </span><span class="RktSym">s</span></td></tr><tr><td><p><span class="RktRes">"..λ.."</span></p></td></tr></table></blockquote></div></p><p>String ordering and case operations are generally
|
||
|
|
<span style="font-style: italic">locale-independent</span>; that is, they work the same for all
|
||
|
|
users. A few <span style="font-style: italic">locale-dependent</span> operations are provided that
|
||
|
|
allow the way that strings are case-folded and sorted to depend on the
|
||
|
|
end-user’s locale. If you’re sorting strings, for example, use
|
||
|
|
<span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string%7E3c%7E3f%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">string<?</a></span> or <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string-ci%7E3c%7E3f%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">string-ci<?</a></span> if the sort result should be
|
||
|
|
consistent across machines and users, but use <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string-locale%7E3c%7E3f%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">string-locale<?</a></span>
|
||
|
|
or <span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string-locale-ci%7E3c%7E3f%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">string-locale-ci<?</a></span> if the sort is purely to order strings
|
||
|
|
for an end user.</p><p><div class="SIntrapara">Examples:</div><div class="SIntrapara"><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string%7E3c%7E3f%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">string<?</a></span><span class="hspace"> </span><span class="RktVal">"apple"</span><span class="hspace"> </span><span class="RktVal">"Banana"</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">#f</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string-ci%7E3c%7E3f%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">string-ci<?</a></span><span class="hspace"> </span><span class="RktVal">"apple"</span><span class="hspace"> </span><span class="RktVal">"Banana"</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">#t</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string-upcase%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">string-upcase</a></span><span class="hspace"> </span><span class="RktVal">"Straße"</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">"STRASSE"</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=parameters.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fmore-scheme..rkt%2529._parameterize%2529%2529&version=8.6" class="RktStxLink Sq" data-pltdoc="x">parameterize</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=encodings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._current-locale%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">current-locale</a></span><span class="hspace"> </span><span class="RktVal">"C"</span><span class="RktPn">]</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=strings.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string-locale-upcase%2529%2529&version=8.6" class="RktValLink Sq" data-pltdoc="x">string-locale-upcase</a></span><span class="hspace"> </span><span class="RktVal">"Straße"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">"STRAßE"</span></p></td></tr></table></blockquote></div></p><p>For working with plain ASCII, working with raw bytes, or
|
||
|
|
encoding/decoding Unicode strings as bytes, use
|
||
|
|
<a href="bytestrings.html" data-pltdoc="x">byte strings</a>.</p><blockquote class="refpara"><blockquote class="refcolumn"><blockquote class="refcontent"><p><span class="imageleft"><img src="magnify.png" alt="+" width="24" height="24"/></span><a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=strings.html&version=8.6" class="Sq" data-pltdoc="x">Strings</a> in <a href="https://download.racket-lang.org/releases/8.6/doc/local-redirect/index.html?doc=reference&rel=index.html&version=8.6" class="Sq" data-pltdoc="x">The Racket Reference</a> provides more on strings and string procedures.</p></blockquote></blockquote></blockquote><div class="navsetbottom"><span class="navleft"><form class="searchform"><input class="searchbox" id="searchbox" type="text" tabindex="1" placeholder="...search manuals..." title="Enter a search string to search the manuals" onkeypress="return DoSearchKey(event, this, "8.6", "../");"/></form> <a href="https://docs.racket-lang.org/index.html" title="up to the documentation top" data-pltdoc="x" onclick="return GotoPLTRoot("8.6");">top</a><span class="tocsettoggle"> <a href="javascript:void(0);" title="show/hide table of contents" onclick="TocsetToggle();">contents</a></span></span><span class="navright"> <a href="characters.html" title="backward to "3.3 Characters"" data-pltdoc="x">← prev</a> <a href="datatypes.html" title="up to "3 Built-In Datatypes"" data-pltdoc="x">up</a> <a href="bytestrings.html" title="forward to "3.5 Bytes and Byte Strings"" data-pltdoc="x">next →</a></span> </div></div></div><div id="contextindicator"> </div></body></html>
|