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<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>13.7.1 Readtables</title><link rel="stylesheet" type="text/css" href="../scribble.css" title="default"/><link rel="stylesheet" type="text/css" href="extras.css" title="default"/><link rel="stylesheet" type="text/css" href="../racket.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 Reference</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="model.html" class="tocviewlink" data-pltdoc="x">Language Model</a></td></tr><tr><td align="right">2 </td><td><a href="notation.html" class="tocviewlink" data-pltdoc="x">Notation for Documentation</a></td></tr><tr><td align="right">3 </td><td><a href="syntax.html" class="tocviewlink" data-pltdoc="x">Syntactic Forms</a></td></tr><tr><td align="right">4 </td><td><a href="data.html" class="tocviewlink" data-pltdoc="x">Datatypes</a></td></tr><tr><td align="right">5 </td><td><a href="structures.html" class="tocviewlink" data-pltdoc="x">Structures</a></td></tr><tr><td align="right">6 </td><td><a href="mzlib_class.html" class="tocviewlink" data-pltdoc="x">Classes and Objects</a></td></tr><tr><td align="right">7 </td><td><a href="mzlib_unit.html" class="tocviewlink" data-pltdoc="x">Units</a></td></tr><tr><td align="right">8 </td><td><a href="contracts.html" class="tocviewlink" data-pltdoc="x">Contracts</a></td></tr><tr><td align="right">9 </td><td><a href="match.html" class="tocviewlink" data-pltdoc="x">Pattern Matching</a></td></tr><tr><td align="right">10 </td><td><a href="control.html" class="tocviewlink" data-pltdoc="x">Control Flow</a></td></tr><tr><td align="right">11 </td><td><a href="concurrency.html" class="tocviewlink" data-pltdoc="x">Concurrency and Parallelism</a></td></tr><tr><td align="right">12 </td><td><a href="Macros.html" class="tocviewlink" data-pltdoc="x">Macros</a></td></tr><tr><td align="right">13 </td><td><a href="input-and-output.html" class="tocviewselflink" data-pltdoc="x">Input and Output</a></td></tr><tr><td align="right">14 </td><td><a href="security.html" class="tocviewlink" data-pltdoc="x">Reflection and Security</a></td></tr><tr><td align="right">15 </td><td><a href="os.html" class="tocviewlink" data-pltdoc="x">Operating System</a></td></tr><tr><td align="right">16 </td><td><a href="memory.html" class="tocviewlink" data-pltdoc="x">Memory Management</a></td></tr><tr><td align="right">17 </td><td><a href="unsafe.html" class="tocviewlink" data-pltdoc="x">Unsafe Operations</a></td></tr><tr><td align="right">18 </td><td><a href="running.html" class="tocviewlink" data-pltdoc="x">Running Racket</a></td></tr><tr><td align="right"></td><td><a href="doc-bibliography.html" class="tocviewlink" data-pltdoc="x">Bibliography</a></td></tr><tr><td align="right"></td><td><a href="doc-index.html" class="tocviewlink" data-pltdoc="x">Index</a></td></tr></table></div></div><div class="tocviewlist"><table cellspacing="0" cellpadding="0"><tr><td style="width: 1em;"><a href="javascript:void(0);" title="Expand/Collapse" class="tocviewtoggle" onclick="TocviewToggle(this,"tocview_1");">►</a></td><td>13 </td><td><a href="input-and-output.html" class="tocviewlink" data-pltdoc="x">Input and Output</a></td></tr></table><div class="tocviewsublist" style="display: none;" id="tocview_1"><table cellspacing="0" cellpadding="0"><tr><td align="right">13.1 </td><td><a href="ports.html" class="tocviewlink" data-pltdoc="x">Ports</a></td></tr><tr><td align="right">13.2 </td><td><a href="Byte_and_String_Input.html" class="tocviewlink" data-pltdoc="x">Byte and String Input</a></td></tr><tr><td align="right">13.3 </td><td><a href="Byte_and_String_Output.html" class="tocviewlink" data-pltdoc="x">Byte and String Output</a></td></tr><tr><td align="right">13.4 </td><td><a href="Reading.html" class="tocviewlink" data-pltdoc="x">Reading</a></td></tr><tr><td align="right">13.5 </td><td><a href="Writing.html" class="tocviewlink" data-pltdoc="x">Writing</a></td></tr><tr><td align="right">13.6 </td><td><a href="pretty-print.html" class="tocviewlink" data-pltdoc="x">Pretty Printing</a></td></tr><tr><td align="right">13.7 </td><td><a href="Reader_Extension.html" class="tocviewselflink" data-pltdoc="x">Reader Extension</a></td></tr><tr><td align="right">13.8 </td><td><a href="Printer_Extension.html" class="tocviewlink" data-pltdoc="x">Printer Extension</a></td></tr><tr><td align="right">13.9 </td><td><a href="serialization.html" class="tocviewlink" data-pltdoc="x">Serialization</a></td></tr><tr><td align="right">13.10 </td><td><a href="fasl.html" class="tocviewlink" data-pltdoc="x">Fast-<wbr></wbr>Load Serialization</a></td></tr><tr><td align="right">13.11 </td><td><a href="sha.html" class="tocviewlink" data-pltdoc="x">Cryptographic Hashing</a></td></tr></table></div></div><div class="tocviewlist"><table cellspacing="0" cellpadding="0"><tr><td style="width: 1em;"><a href="javascript:void(0);" title="Expand/Collapse" class="tocviewtoggle" onclick="TocviewToggle(this,"tocview_2");">▼</a></td><td>13.7 </td><td><a href="Reader_Extension.html" class="tocviewlink" data-pltdoc="x">Reader Extension</a></td></tr></table><div class="tocviewsublistbottom" style="display: block;" id="tocview_2"><table cellspacing="0" cellpadding="0"><tr><td align="right">13.7.1 </td><td><a href="readtables.html" class="tocviewselflink" data-pltdoc="x">Readtables</a></td></tr><tr><td align="right">13.7.2 </td><td><a href="reader-procs.html" class="tocviewlink" data-pltdoc="x">Reader-<wbr></wbr>Extension Procedures</a></td></tr><tr><td align="right">13.7.3 </td><td><a href="special-comments.html" class="tocviewlink" data-pltdoc="x">Special Comments</a></td></tr></table></div></div></div><div class="tocsub"><div class="tocsubtitle">On this page:</div><table class="tocsublist" cellspacing="0"><tr><td><a href="readtables.html#%28def._%28%28quote._~23~25kernel%29._readtable~3f%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">readtable?</span></span></a></td></tr><tr><td><a href="readtables.html#%28def._%28%28quote._~23~25kernel%29._make-readtable%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">make-<wbr></wbr>readtable</span></span></a></td></tr><tr><td><a href="readtables.html#%28def._%28%28quote._~23~25kernel%29._readtable-mapping%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">readtable-<wbr></wbr>mapping</span></span></a></td></tr></table></div></div><div class="maincolumn"><div class="main"><div class="navsettop"><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="Reader_Extension.html" title="backward to "13.7 Reader Extension"" data-pltdoc="x">← prev</a> <a href="Reader_Extension.html" title="up to "13.7 Reader Extension"" data-pltdoc="x">up</a> <a href="reader-procs.html" title="forward to "13.7.2 Reader-Extension Procedures"" data-pltdoc="x">next →</a></span> </div><h5 x-source-module="(lib "scribblings/reference/reference.scrbl")" x-source-pkg="racket-doc" x-part-tag=""readtables"">13.7.1<tt> </tt><a name="(part._readtables)"></a>Readtables</h5><p>The dispatch table in <a href="reader.html#%28part._default-readtable-dispatch%29" data-pltdoc="x">Delimiters and Dispatch</a>
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corresponds to the default <a name="(tech._readtable)"></a><span style="font-style: italic">readtable</span>. By creating a new
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readtable and installing it via the <span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._current-readtable%29%29" class="RktValLink" data-pltdoc="x">current-readtable</a></span>
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parameter, the reader’s behavior can be extended.</p><p>A readtable is consulted at specific times by the reader:</p><ul><li><p>when looking for the start of a datum;</p></li><li><p>when determining how to parse a datum that starts with
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<span class="RktInBG"><span class="hspace"></span><span class="RktIn">#</span><span class="hspace"></span></span>;</p></li><li><p>when looking for a delimiter to terminate a symbol or number;</p></li><li><p>when looking for an opener (such as <span class="RktInBG"><span class="hspace"></span><span class="RktIn">(</span><span class="hspace"></span></span>), closer (such
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as <span class="RktInBG"><span class="hspace"></span><span class="RktIn">)</span><span class="hspace"></span></span>), or <span class="RktInBG"><span class="hspace"></span><span class="RktIn">.</span><span class="hspace"></span></span> after the first character parsed as
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a sequence for a pair, list, vector, or hash table; or</p></li><li><p>when looking for an opener after <span class="RktInBG"><span class="hspace"></span><span class="RktIn">#</span><span class="hspace"></span></span><span class="sroman">‹<span style="font-style: italic">n</span>›</span> in a
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vector of specified length <span class="sroman">‹<span style="font-style: italic">n</span>›</span>.</p></li></ul><p>The readtable is ignored at other times. In particular, after parsing
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a character that is mapped to the default behavior of <span class="RktInBG"><span class="hspace"></span><span class="RktIn">;</span><span class="hspace"></span></span>, the
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readtable is ignored until the comment’s terminating newline is
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discovered. Similarly, the readtable does not affect string parsing
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until a closing double-quote is found. Meanwhile, if a character is
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mapped to the default behavior of <span class="RktInBG"><span class="hspace"></span><span class="RktIn">(</span><span class="hspace"></span></span>, then it starts sequence
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that is closed by any character that is mapped to a closing parenthesis
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<span class="RktInBG"><span class="hspace"></span><span class="RktIn">)</span><span class="hspace"></span></span>. An apparent exception is that the default parsing of
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<span class="RktInBG"><span class="hspace"></span><span class="RktIn">|</span><span class="hspace"></span></span> quotes a symbol until a matching character is found, but
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the parser is simply using the character that started the quote; it
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does not consult the readtable.</p><p>For many contexts, <span class="RktVal">#f</span> identifies the default readtable. In
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particular, <span class="RktVal">#f</span> is the initial value for the
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<span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._current-readtable%29%29" class="RktValLink" data-pltdoc="x">current-readtable</a></span> parameter, which causes the reader to
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behave as described in <a href="reader.html" data-pltdoc="x">The Reader</a>.</p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._readtable~3f))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="readtables.html#%28def._%28%28quote._~23~25kernel%29._readtable~3f%29%29" class="RktValDef RktValLink" data-pltdoc="x">readtable?</a></span></span><span class="hspace"> </span><span class="RktVar">v</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="booleans.html#%28def._%28%28quote._~23~25kernel%29._boolean~3f%29%29" class="RktValLink" data-pltdoc="x">boolean?</a></span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">v</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fprivate%2Fmisc..rkt%29._any%2Fc%29%29" class="RktValLink" data-pltdoc="x">any/c</a></span></td></tr></table></blockquote></div><div class="SIntrapara">Returns <span class="RktVal">#t</span> if <span class="RktVar">v</span> is a readtable, <span class="RktVal">#f</span>
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otherwise.</div></p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._make-readtable))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="readtables.html#%28def._%28%28quote._~23~25kernel%29._make-readtable%29%29" class="RktValDef RktValLink" data-pltdoc="x">make-readtable</a></span></span><span class="hspace"> </span><span class="RktVar">readtable</span><span class="hspace"> </span><span class="RktVar">key</span><span class="hspace"> </span><span class="RktVar">mode</span><span class="hspace"> </span><span class="RktVar">action</span><span class="hspace"> </span><span class="RktMeta">...</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="readtables.html#%28def._%28%28quote._~23~25kernel%29._readtable~3f%29%29" class="RktValLink" data-pltdoc="x">readtable?</a></span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">readtable</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._or%2Fc%29%29" class="RktValLink" data-pltdoc="x">or/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="readtables.html#%28def._%28%28quote._~23~25kernel%29._readtable~3f%29%29" class="RktValLink" data-pltdoc="x">readtable?</a></span><span class="hspace"> </span><span class="RktVal">#f</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">key</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._or%2Fc%29%29" class="RktValLink" data-pltdoc="x">or/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="characters.html#%28def._%28%28quote._~23~25kernel%29._char~3f%29%29" class="RktValLink" data-pltdoc="x">char?</a></span><span class="hspace"> </span><span class="RktVal">#f</span><span class="RktPn">)</span></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="argcontract"><tr><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktVar">mode</span></td><td valign="top"><span class="hspace"> </span></td><td valign="top">:</td><td valign="top"><span class="hspace"> </span></td><td valign="top"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._or%2Fc%29%29" class="RktValLink" data-pltdoc="x">or/c</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">terminating-macro</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">non-terminating-macro</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">dispatch-macro</span></td></tr><tr><td><span class="hspace"> </span><span class="RktSym"><a href="characters.html#%28def._%28%28quote._~23~25kernel%29._char~3f%29%29" class="RktValLink" data-pltdoc="x">char?</a></span><span class="RktPn">)</span></td></tr></table></td></tr></table></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="argcontract"><tr><td valign="top"><span class="hspace"> </span></td><td valign="top"><span class="RktVar">action</span></td><td valign="top"><span class="hspace"> </span></td><td valign="top">:</td><td valign="top"><span class="hspace"> </span></td><td valign="top"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._or%2Fc%29%29" class="RktValLink" data-pltdoc="x">or/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="procedures.html#%28def._%28%28quote._~23~25kernel%29._procedure~3f%29%29" class="RktValLink" data-pltdoc="x">procedure?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktSym"><a href="readtables.html#%28def._%28%28quote._~23~25kernel%29._readtable~3f%29%29" class="RktValLink" data-pltdoc="x">readtable?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVal">#f</span><span class="RktPn">)</span></td></tr></table></td></tr></table></td></tr></table></blockquote></div><div class="SIntrapara">Creates a new readtable that is like <span class="RktVar">readtable</span> (which can be
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<span class="RktVal">#f</span> to indicate the default readtable),
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except that the reader’s behavior is modified for each
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<span class="RktVar">key</span> according to the given <span class="RktVar">mode</span> and
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<span class="RktVar">action</span>. The <span class="RktSym"><a href="stx-patterns.html#%28form._%28%28lib._racket%2Fprivate%2Fstxcase-scheme..rkt%29._......%29%29" class="RktStxLink" data-pltdoc="x">...</a></span> for <span class="RktSym"><a href="readtables.html#%28def._%28%28quote._~23~25kernel%29._make-readtable%29%29" class="RktValLink" data-pltdoc="x">make-readtable</a></span> applies
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to all three of <span class="RktVar">key</span>, <span class="RktVar">mode</span>, and <span class="RktVar">action</span>; in
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other words, the total number of arguments to <span class="RktSym"><a href="readtables.html#%28def._%28%28quote._~23~25kernel%29._make-readtable%29%29" class="RktValLink" data-pltdoc="x">make-readtable</a></span>
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must be <span style="font-style: italic"></span>1<span style="font-style: italic"></span> modulo <span style="font-style: italic"></span>3<span style="font-style: italic"></span>.</div></p><p>The possible combinations for <span class="RktVar">key</span>, <span class="RktVar">mode</span>, and
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<span class="RktVar">action</span> are as follows:</p><ul><li><p><span class="RktVar">char</span><span class="stt"> </span><a name="(idx._(gentag._269._(lib._scribblings/reference/reference..scrbl)))"></a><span class="RktVal">'</span><span class="RktVal">terminating-macro</span><span class="stt"> </span><span class="RktVar">proc</span> —<wbr></wbr> causes
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<span class="RktVar">char</span> to be parsed as a delimiter, and an
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unquoted/uncommented <span class="RktVar">char</span> in the input string triggers a
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call to the <a name="(tech._reader._macro)"></a><span style="font-style: italic">reader macro</span> <span class="RktVar">proc</span>; the activity of
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<span class="RktVar">proc</span> is described further below. Conceptually, characters
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like <span class="RktInBG"><span class="hspace"></span><span class="RktIn">;</span><span class="hspace"></span></span>, <span class="RktInBG"><span class="hspace"></span><span class="RktIn">(</span><span class="hspace"></span></span>, and <span class="RktInBG"><span class="hspace"></span><span class="RktIn">)</span><span class="hspace"></span></span> are mapped to
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terminating reader macros in the default readtable.</p></li><li><p><span class="RktVar">char</span><span class="stt"> </span><a name="(idx._(gentag._270._(lib._scribblings/reference/reference..scrbl)))"></a><span class="RktVal">'</span><span class="RktVal">non-terminating-macro</span><span class="stt"> </span><span class="RktVar">proc</span> —<wbr></wbr> like
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the <span class="RktVal">'</span><span class="RktVal">terminating-macro</span> variant, but <span class="RktVar">char</span> is not
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treated as a delimiter, so it can be used in the middle of an
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identifier or number. Conceptually, <span class="RktInBG"><span class="hspace"></span><span class="RktIn">#</span><span class="hspace"></span></span> is mapped to a
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non-terminating macro in the default readtable.</p></li><li><p><span class="RktVar">char</span><span class="stt"> </span><a name="(idx._(gentag._271._(lib._scribblings/reference/reference..scrbl)))"></a><span class="RktVal">'</span><span class="RktVal">dispatch-macro</span><span class="stt"> </span><span class="RktVar">proc</span> —<wbr></wbr> like the
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<span class="RktVal">'</span><span class="RktVal">non-terminating-macro</span> variant, but for <span class="RktVar">char</span> only
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when it follows a <span class="RktInBG"><span class="hspace"></span><span class="RktIn">#</span><span class="hspace"></span></span> (or, more precisely, when the character
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follows one that has been mapped to the behavior of <span class="RktInBG"><span class="hspace"></span><span class="RktIn">#</span><span class="hspace"></span></span>
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in the default readtable).</p></li><li><p><span class="RktVar">char</span><span class="stt"> </span><span class="RktVar">like-char</span><span class="stt"> </span><span class="RktVar">readtable</span> —<wbr></wbr> causes
|
|
<span class="RktVar">char</span> to be parsed in the same way that <span class="RktVar">like-char</span>
|
|
is parsed in <span class="RktVar">readtable</span>, where <span class="RktVar">readtable</span> can be
|
|
<span class="RktVal">#f</span> to indicate the default readtable. (The mapping of
|
|
<span class="RktVar">char</span> does not apply after <span class="RktInBG"><span class="hspace"></span><span class="RktIn">#</span><span class="hspace"></span></span>, which is configured
|
|
separately via <span class="RktVal">'</span><span class="RktVal">dispatch-macro</span>.) Mapping a character to
|
|
the same actions as <span class="RktInBG"><span class="hspace"></span><span class="RktIn">|</span><span class="hspace"></span></span> in the default reader means that the
|
|
character starts quoting for symbols, and the same character
|
|
terminates the quote; in contrast, mapping a character to the same
|
|
action as a <span class="RktInBG"><span class="hspace"></span><span class="RktIn">"</span><span class="hspace"></span></span> means that the character starts a string, but
|
|
the string is still terminated with a closing <span class="RktInBG"><span class="hspace"></span><span class="RktIn">"</span><span class="hspace"></span></span>. Finally,
|
|
mapping a character to an action in the default readtable means that
|
|
the character’s behavior is sensitive to parameters that affect the
|
|
original character; for example, mapping a character to the same
|
|
action as a curly brace <span class="RktInBG"><span class="hspace"></span><span class="RktIn">{</span><span class="hspace"></span></span> in the default readtable means
|
|
that the character is disallowed when the
|
|
<span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._read-curly-brace-as-paren%29%29" class="RktValLink" data-pltdoc="x">read-curly-brace-as-paren</a></span> parameter is set to <span class="RktVal">#f</span>.</p></li><li><p><span class="RktVal">#f</span><span class="stt"> </span><a name="(idx._(gentag._272._(lib._scribblings/reference/reference..scrbl)))"></a><span class="RktVal">'</span><span class="RktVal">non-terminating-macro</span><span class="stt"> </span><span class="RktVar">proc</span> —<wbr></wbr>
|
|
replaces the macro used to parse characters with no specific mapping:
|
|
i.e., the characters (other than <span class="RktInBG"><span class="hspace"></span><span class="RktIn">#</span><span class="hspace"></span></span> or <span class="RktInBG"><span class="hspace"></span><span class="RktIn">|</span><span class="hspace"></span></span>) that can
|
|
start a symbol or number with the default readtable.</p></li></ul><p>If multiple <span class="RktVal">'</span><span class="RktVal">dispatch-macro</span> mappings are provided for a
|
|
single <span class="RktVar">char</span>, all but the last one are ignored. Similarly, if
|
|
multiple non-<span class="RktVal">'</span><span class="RktVal">dispatch-macro</span> mappings are provided for a
|
|
single <span class="RktVar">char</span>, all but the last one are ignored.</p><p>A reader macro <span class="RktVar">proc</span> must accept six arguments, and it can
|
|
optionally accept two arguments. The first two arguments are always
|
|
the character that triggered the reader macro and the input port for
|
|
reading. When the reader macro is triggered by <span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._read-syntax%29%29" class="RktValLink" data-pltdoc="x">read-syntax</a></span>
|
|
(or <span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._read-syntax%2Frecursive%29%29" class="RktValLink" data-pltdoc="x">read-syntax/recursive</a></span>), the procedure is passed four
|
|
additional arguments that represent a source location for
|
|
already-consumed character(s): the source name, a line number or
|
|
<span class="RktVal">#f</span>, a column number or <span class="RktVal">#f</span>, and a position or
|
|
<span class="RktVal">#f</span>. When the reader macro is triggered by <span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._read%29%29" class="RktValLink" data-pltdoc="x">read</a></span> (or
|
|
<span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._read%2Frecursive%29%29" class="RktValLink" data-pltdoc="x">read/recursive</a></span>), the procedure is passed only two arguments
|
|
if it accepts two arguments, otherwise it is passed six arguments
|
|
where the third is always <span class="RktVal">#f</span>. See <a href="reader-procs.html" data-pltdoc="x">Reader-Extension Procedures</a>
|
|
for information on the procedure’s results.</p><p>A reader macro normally reads characters from the given input port to
|
|
produce a value to be used as the “reader macro-expansion” of the
|
|
consumed characters. The reader macro might produce a special-comment
|
|
value (see <a href="special-comments.html" data-pltdoc="x">Special Comments</a>) to cause the consumed
|
|
character to be treated as whitespace, and it might use
|
|
<span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._read%2Frecursive%29%29" class="RktValLink" data-pltdoc="x">read/recursive</a></span> or <span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._read-syntax%2Frecursive%29%29" class="RktValLink" data-pltdoc="x">read-syntax/recursive</a></span>.</p><p><div class="SIntrapara"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><blockquote class="SubFlow"><div class="RBackgroundLabel SIEHidden"><div class="RBackgroundLabelInner"><p>procedure</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(def._((quote._~23~25kernel)._readtable-mapping))"></a><span title="Provided from: racket/base, racket | Package: base"><span class="RktSym"><a href="readtables.html#%28def._%28%28quote._~23~25kernel%29._readtable-mapping%29%29" class="RktValDef RktValLink" data-pltdoc="x">readtable-mapping</a></span></span><span class="hspace"> </span><span class="RktVar">readtable</span><span class="hspace"> </span><span class="RktVar">char</span><span class="RktPn">)</span></p></blockquote></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="prototype"><tr><td valign="top"><span class="hspace"> </span></td><td valign="top">→</td><td valign="top"><span class="hspace"> </span></td><td valign="top"><table cellspacing="0" cellpadding="0"><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._or%2Fc%29%29" class="RktValLink" data-pltdoc="x">or/c</a></span><span class="hspace"> </span><span class="RktSym"><a href="characters.html#%28def._%28%28quote._~23~25kernel%29._char~3f%29%29" class="RktValLink" data-pltdoc="x">char?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">terminating-macro</span></td></tr><tr><td><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">non-terminating-macro</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._or%2Fc%29%29" class="RktValLink" data-pltdoc="x">or/c</a></span><span class="hspace"> </span><span class="RktVal">#f</span><span class="hspace"> </span><span class="RktSym"><a href="procedures.html#%28def._%28%28quote._~23~25kernel%29._procedure~3f%29%29" class="RktValLink" data-pltdoc="x">procedure?</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="data-structure-contracts.html#%28def._%28%28lib._racket%2Fcontract%2Fbase..rkt%29._or%2Fc%29%29" class="RktValLink" data-pltdoc="x">or/c</a></span><span class="hspace"> </span><span class="RktVal">#f</span><span class="hspace"> </span><span class="RktSym"><a href="procedures.html#%28def._%28%28quote._~23~25kernel%29._procedure~3f%29%29" class="RktValLink" data-pltdoc="x">procedure?</a></span><span class="RktPn">)</span></td></tr></table></td></tr></table></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">readtable</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="readtables.html#%28def._%28%28quote._~23~25kernel%29._readtable~3f%29%29" class="RktValLink" data-pltdoc="x">readtable?</a></span></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">char</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktSym"><a href="characters.html#%28def._%28%28quote._~23~25kernel%29._char~3f%29%29" class="RktValLink" data-pltdoc="x">char?</a></span></td></tr></table></blockquote></div><div class="SIntrapara">Produces information about the mappings in <span class="RktVar">readtable</span> for
|
|
<span class="RktVar">char</span>. The result is three values:</div></p><ul><li><p>either a character (mapping to the same behavior as the
|
|
character in the default readtable), <span class="RktVal">'</span><span class="RktVal">terminating-macro</span>, or
|
|
<span class="RktVal">'</span><span class="RktVal">non-terminating-macro</span>; this result reports the main (i.e.,
|
|
non-<span class="RktVal">'</span><span class="RktVal">dispatch-macro</span>) mapping for <span class="RktVar">char</span>. When the result
|
|
is a character, then <span class="RktVar">char</span> is mapped to the same behavior as the
|
|
returned character in the default readtable.</p></li><li><p>either <span class="RktVal">#f</span> or a reader-macro procedure; the result is a
|
|
procedure when the first result is <span class="RktVal">'</span><span class="RktVal">terminating-macro</span> or
|
|
<span class="RktVal">'</span><span class="RktVal">non-terminating-macro</span>.</p></li><li><p>either <span class="RktVal">#f</span> or a reader-macro procedure; the result is a
|
|
procedure when the character has a <span class="RktVal">'</span><span class="RktVal">dispatch-macro</span> mapping in
|
|
<span class="RktVar">readtable</span> to override the default dispatch behavior.</p></li></ul><p>Note that reader-macro procedures for the default readtable are not
|
|
directly accessible. To invoke default behaviors, use
|
|
<span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._read%2Frecursive%29%29" class="RktValLink" data-pltdoc="x">read/recursive</a></span> or <span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._read-syntax%2Frecursive%29%29" class="RktValLink" data-pltdoc="x">read-syntax/recursive</a></span> with a
|
|
character and the <span class="RktVal">#f</span> readtable.</p><p><div class="SIntrapara">Examples:</div><div class="SIntrapara"><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">Provides </span><span class="RktSym">raise-read-error</span><span class="RktCmt"> and </span><span class="RktSym">raise-read-eof-error</span></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="require.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._require%29%29" class="RktStxLink" data-pltdoc="x">require</a></span><span class="hspace"> </span><span class="RktSym">syntax/readerr</span><span class="RktPn">)</span></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="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">skip-whitespace</span><span class="hspace"> </span><span class="RktSym">port</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">Skips whitespace characters, sensitive to the current</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">readtable</span><span class="RktCmt">'</span><span class="RktCmt">s definition of whitespace</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="let.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._let%29%29" class="RktStxLink" data-pltdoc="x">let</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym">ch</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="Byte_and_String_Input.html#%28def._%28%28quote._~23~25kernel%29._peek-char%29%29" class="RktValLink" data-pltdoc="x">peek-char</a></span><span class="hspace"> </span><span class="RktSym">port</span><span class="RktPn">)</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="when_unless.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._unless%29%29" class="RktStxLink" data-pltdoc="x">unless</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="port-ops.html#%28def._%28%28quote._~23~25kernel%29._eof-object~3f%29%29" class="RktValLink" data-pltdoc="x">eof-object?</a></span><span class="hspace"> </span><span class="RktSym">ch</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">Consult current readtable:</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="let.html#%28form._%28%28quote._~23~25kernel%29._let-values%29%29" class="RktStxLink" data-pltdoc="x">let-values</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktPn">(</span><span class="RktSym">like-ch/sym</span><span class="hspace"> </span><span class="RktSym">proc</span><span class="hspace"> </span><span class="RktSym">dispatch-proc</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="readtables.html#%28def._%28%28quote._~23~25kernel%29._readtable-mapping%29%29" class="RktValLink" data-pltdoc="x">readtable-mapping</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._current-readtable%29%29" class="RktValLink" data-pltdoc="x">current-readtable</a></span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktSym">ch</span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">If like-ch/sym is whitespace, then ch is whitespace</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="when_unless.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._when%29%29" class="RktStxLink" data-pltdoc="x">when</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="if.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._and%29%29" class="RktStxLink" data-pltdoc="x">and</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="characters.html#%28def._%28%28quote._~23~25kernel%29._char~3f%29%29" class="RktValLink" data-pltdoc="x">char?</a></span><span class="hspace"> </span><span class="RktSym">like-ch/sym</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="characters.html#%28def._%28%28quote._~23~25kernel%29._char-whitespace~3f%29%29" class="RktValLink" data-pltdoc="x">char-whitespace?</a></span><span class="hspace"> </span><span class="RktSym">like-ch/sym</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="Byte_and_String_Input.html#%28def._%28%28quote._~23~25kernel%29._read-char%29%29" class="RktValLink" data-pltdoc="x">read-char</a></span><span class="hspace"> </span><span class="RktSym">port</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">skip-whitespace</span><span class="hspace"> </span><span class="RktSym">port</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></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="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">skip-comments</span><span class="hspace"> </span><span class="RktSym">read-one</span><span class="hspace"> </span><span class="RktSym">port</span><span class="hspace"> </span><span class="RktSym">src</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">Recursive read, but skip comments and detect EOF</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="let.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._let%29%29" class="RktStxLink" data-pltdoc="x">let</a></span><span class="hspace"> </span><span class="RktSym">loop</span><span class="hspace"> </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="let.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._let%29%29" class="RktStxLink" data-pltdoc="x">let</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym">v</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">read-one</span><span class="RktPn">)</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="if.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._cond%29%29" class="RktStxLink" data-pltdoc="x">cond</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">[</span><span class="RktPn">(</span><span class="RktSym"><a href="special-comments.html#%28def._%28%28quote._~23~25kernel%29._special-comment~3f%29%29" class="RktValLink" data-pltdoc="x">special-comment?</a></span><span class="hspace"> </span><span class="RktSym">v</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">loop</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="RktPn">(</span><span class="RktSym"><a href="port-ops.html#%28def._%28%28quote._~23~25kernel%29._eof-object~3f%29%29" class="RktValLink" data-pltdoc="x">eof-object?</a></span><span class="hspace"> </span><span class="RktSym">v</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="let.html#%28form._%28%28quote._~23~25kernel%29._let-values%29%29" class="RktStxLink" data-pltdoc="x">let-values</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktPn">(</span><span class="RktSym">l</span><span class="hspace"> </span><span class="RktSym">c</span><span class="hspace"> </span><span class="RktSym">p</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="linecol.html#%28def._%28%28quote._~23~25kernel%29._port-next-location%29%29" class="RktValLink" data-pltdoc="x">port-next-location</a></span><span class="hspace"> </span><span class="RktSym">port</span><span class="RktPn">)</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">raise-read-eof-error</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktVal">"unexpected EOF in tuple"</span><span class="hspace"> </span><span class="RktSym">src</span><span class="hspace"> </span><span class="RktSym">l</span><span class="hspace"> </span><span class="RktSym">c</span><span class="hspace"> </span><span class="RktSym">p</span><span class="hspace"> </span><span class="RktVal">1</span><span class="RktPn">)</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="if.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._else%29%29" class="RktStxLink" data-pltdoc="x">else</a></span><span class="hspace"> </span><span class="RktSym">v</span><span class="RktPn">]</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></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="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">parse</span><span class="hspace"> </span><span class="RktSym">port</span><span class="hspace"> </span><span class="RktSym">read-one</span><span class="hspace"> </span><span class="RktSym">src</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">First, check for empty tuple</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">skip-whitespace</span><span class="hspace"> </span><span class="RktSym">port</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="if.html#%28form._%28%28quote._~23~25kernel%29._if%29%29" class="RktStxLink" data-pltdoc="x">if</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="Equality.html#%28def._%28%28quote._~23~25kernel%29._eq~3f%29%29" class="RktValLink" data-pltdoc="x">eq?</a></span><span class="hspace"> </span><span class="RktVal">#\></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="Byte_and_String_Input.html#%28def._%28%28quote._~23~25kernel%29._peek-char%29%29" class="RktValLink" data-pltdoc="x">peek-char</a></span><span class="hspace"> </span><span class="RktSym">port</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktSym"><a href="pairs.html#%28def._%28%28quote._~23~25kernel%29._null%29%29" class="RktValLink" data-pltdoc="x">null</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="let.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._let%29%29" class="RktStxLink" data-pltdoc="x">let</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym">elem</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">read-one</span><span class="RktPn">)</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="if.html#%28form._%28%28quote._~23~25kernel%29._if%29%29" class="RktStxLink" data-pltdoc="x">if</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="special-comments.html#%28def._%28%28quote._~23~25kernel%29._special-comment~3f%29%29" class="RktValLink" data-pltdoc="x">special-comment?</a></span><span class="hspace"> </span><span class="RktSym">elem</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">Found a comment, so look for > again</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">parse</span><span class="hspace"> </span><span class="RktSym">port</span><span class="hspace"> </span><span class="RktSym">read-one</span><span class="hspace"> </span><span class="RktSym">src</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">Non-empty tuple:</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="pairs.html#%28def._%28%28quote._~23~25kernel%29._cons%29%29" class="RktValLink" data-pltdoc="x">cons</a></span><span class="hspace"> </span><span class="RktSym">elem</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">parse-nonempty</span><span class="hspace"> </span><span class="RktSym">port</span><span class="hspace"> </span><span class="RktSym">read-one</span><span class="hspace"> </span><span class="RktSym">src</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></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="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">parse-nonempty</span><span class="hspace"> </span><span class="RktSym">port</span><span class="hspace"> </span><span class="RktSym">read-one</span><span class="hspace"> </span><span class="RktSym">src</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">Need a comma or closer</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">skip-whitespace</span><span class="hspace"> </span><span class="RktSym">port</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="case.html#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._case%29%29" class="RktStxLink" data-pltdoc="x">case</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="Byte_and_String_Input.html#%28def._%28%28quote._~23~25kernel%29._peek-char%29%29" class="RktValLink" data-pltdoc="x">peek-char</a></span><span class="hspace"> </span><span class="RktSym">port</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">[</span><span class="RktPn">(</span><span class="RktVal">#\></span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="Byte_and_String_Input.html#%28def._%28%28quote._~23~25kernel%29._read-char%29%29" class="RktValLink" data-pltdoc="x">read-char</a></span><span class="hspace"> </span><span class="RktSym">port</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">Done</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktSym"><a href="pairs.html#%28def._%28%28quote._~23~25kernel%29._null%29%29" class="RktValLink" data-pltdoc="x">null</a></span><span class="RktPn">]</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">[</span><span class="RktPn">(</span><span class="RktVal">#\,</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="Byte_and_String_Input.html#%28def._%28%28quote._~23~25kernel%29._read-char%29%29" class="RktValLink" data-pltdoc="x">read-char</a></span><span class="hspace"> </span><span class="RktSym">port</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">Read next element and recur</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="pairs.html#%28def._%28%28quote._~23~25kernel%29._cons%29%29" class="RktValLink" data-pltdoc="x">cons</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">skip-comments</span><span class="hspace"> </span><span class="RktSym">read-one</span><span class="hspace"> </span><span class="RktSym">port</span><span class="hspace"> </span><span class="RktSym">src</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">parse-nonempty</span><span class="hspace"> </span><span class="RktSym">port</span><span class="hspace"> </span><span class="RktSym">read-one</span><span class="hspace"> </span><span class="RktSym">src</span><span class="RktPn">)</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="if.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._else%29%29" class="RktStxLink" data-pltdoc="x">else</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">Either a comment or an error; grab location (in case</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">of error) and read recursively to detect comments</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="let.html#%28form._%28%28quote._~23~25kernel%29._let-values%29%29" class="RktStxLink" data-pltdoc="x">let-values</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktPn">(</span><span class="RktSym">l</span><span class="hspace"> </span><span class="RktSym">c</span><span class="hspace"> </span><span class="RktSym">p</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="linecol.html#%28def._%28%28quote._~23~25kernel%29._port-next-location%29%29" class="RktValLink" data-pltdoc="x">port-next-location</a></span><span class="hspace"> </span><span class="RktSym">port</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="RktPn">(</span><span class="RktSym">v</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">read-one</span><span class="RktPn">)</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="if.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._cond%29%29" class="RktStxLink" data-pltdoc="x">cond</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">[</span><span class="RktPn">(</span><span class="RktSym"><a href="special-comments.html#%28def._%28%28quote._~23~25kernel%29._special-comment~3f%29%29" class="RktValLink" data-pltdoc="x">special-comment?</a></span><span class="hspace"> </span><span class="RktSym">v</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">It was a comment, so try again</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">parse-nonempty</span><span class="hspace"> </span><span class="RktSym">port</span><span class="hspace"> </span><span class="RktSym">read-one</span><span class="hspace"> </span><span class="RktSym">src</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="if.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._else%29%29" class="RktStxLink" data-pltdoc="x">else</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">Wasn</span><span class="RktCmt">'</span><span class="RktCmt">t a comment, comma, or closer; error</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">(</span><span class="RktSym"><a href="if.html#%28form._%28%28quote._~23~25kernel%29._if%29%29" class="RktStxLink" data-pltdoc="x">if</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="port-ops.html#%28def._%28%28quote._~23~25kernel%29._eof-object~3f%29%29" class="RktValLink" data-pltdoc="x">eof-object?</a></span><span class="hspace"> </span><span class="RktSym">v</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktSym">raise-read-eof-error</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktSym">raise-read-error</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktVal">"expected `,` or `>`"</span><span class="hspace"> </span><span class="RktSym">src</span><span class="hspace"> </span><span class="RktSym">l</span><span class="hspace"> </span><span class="RktSym">c</span><span class="hspace"> </span><span class="RktSym">p</span><span class="hspace"> </span><span class="RktVal">1</span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></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="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">make-delims-table</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">Table to use for recursive reads to disallow delimiters</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt"> (except those in sub-expressions)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="let.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._letrec%29%29" class="RktStxLink" data-pltdoc="x">letrec</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym">misplaced-delimiter</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="lambda.html#%28form._%28%28quote._~23~25kernel%29._case-lambda%29%29" class="RktStxLink" data-pltdoc="x">case-lambda</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">[</span><span class="RktPn">(</span><span class="RktSym">ch</span><span class="hspace"> </span><span class="RktSym">port</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">misplaced-delimiter</span><span class="hspace"> </span><span class="RktSym">ch</span><span class="hspace"> </span><span class="RktSym">port</span><span class="hspace"> </span><span class="RktVal">#f</span><span class="hspace"> </span><span class="RktVal">#f</span><span class="hspace"> </span><span class="RktVal">#f</span><span class="hspace"> </span><span class="RktVal">#f</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="RktPn">(</span><span class="RktSym">ch</span><span class="hspace"> </span><span class="RktSym">port</span><span class="hspace"> </span><span class="RktSym">src</span><span class="hspace"> </span><span class="RktSym">line</span><span class="hspace"> </span><span class="RktSym">col</span><span class="hspace"> </span><span class="RktSym">pos</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">raise-read-error</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="Writing.html#%28def._%28%28quote._~23~25kernel%29._format%29%29" class="RktValLink" data-pltdoc="x">format</a></span><span class="hspace"> </span><span class="RktVal">"misplaced `~a` in tuple"</span><span class="hspace"> </span><span class="RktSym">ch</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktSym">src</span><span class="hspace"> </span><span class="RktSym">line</span><span class="hspace"> </span><span class="RktSym">col</span><span class="hspace"> </span><span class="RktSym">pos</span><span class="hspace"> </span><span class="RktVal">1</span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</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="readtables.html#%28def._%28%28quote._~23~25kernel%29._make-readtable%29%29" class="RktValLink" data-pltdoc="x">make-readtable</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._current-readtable%29%29" class="RktValLink" data-pltdoc="x">current-readtable</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktVal">#\,</span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">terminating-macro</span><span class="hspace"> </span><span class="RktSym">misplaced-delimiter</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktVal">#\></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">terminating-macro</span><span class="hspace"> </span><span class="RktSym">misplaced-delimiter</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></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="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">wrap</span><span class="hspace"> </span><span class="RktSym">l</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktVal">`</span><span class="RktVal">(</span><span class="RktVal">make-tuple</span><span class="hspace"> </span><span class="RktVal">(</span><span class="RktVal">list</span><span class="hspace"> </span><span class="RktRdr">,@</span><span class="RktSym">l</span><span class="RktVal">)</span><span class="RktVal">)</span><span class="RktPn">)</span></td></tr></table></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="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">parse-open-tuple</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="lambda.html#%28form._%28%28quote._~23~25kernel%29._case-lambda%29%29" class="RktStxLink" data-pltdoc="x">case-lambda</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">[</span><span class="RktPn">(</span><span class="RktSym">ch</span><span class="hspace"> </span><span class="RktSym">port</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">‘</span><span class="RktCmt">read</span><span class="RktCmt">‘</span><span class="RktCmt"> mode</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">wrap</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">parse</span><span class="hspace"> </span><span class="RktSym">port</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span><span class="hspace"> </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="Reading.html#%28def._%28%28quote._~23~25kernel%29._read%2Frecursive%29%29" class="RktValLink" data-pltdoc="x">read/recursive</a></span><span class="hspace"> </span><span class="RktSym">port</span><span class="hspace"> </span><span class="RktVal">#f</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">make-delims-table</span><span class="RktPn">)</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="inspectors.html#%28def._%28%28quote._~23~25kernel%29._object-name%29%29" class="RktValLink" data-pltdoc="x">object-name</a></span><span class="hspace"> </span><span class="RktSym">port</span><span class="RktPn">)</span><span class="RktPn">)</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="RktPn">(</span><span class="RktSym">ch</span><span class="hspace"> </span><span class="RktSym">port</span><span class="hspace"> </span><span class="RktSym">src</span><span class="hspace"> </span><span class="RktSym">line</span><span class="hspace"> </span><span class="RktSym">col</span><span class="hspace"> </span><span class="RktSym">pos</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktCmt">;</span><span class="RktCmt"> </span><span class="RktCmt">‘</span><span class="RktCmt">read-syntax</span><span class="RktCmt">‘</span><span class="RktCmt"> mode</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="stxops.html#%28def._%28%28quote._~23~25kernel%29._datum-~3esyntax%29%29" class="RktValLink" data-pltdoc="x">datum->syntax</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktVal">#f</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">wrap</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">parse</span><span class="hspace"> </span><span class="RktSym">port</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span><span class="hspace"> </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="Reading.html#%28def._%28%28quote._~23~25kernel%29._read-syntax%2Frecursive%29%29" class="RktValLink" data-pltdoc="x">read-syntax/recursive</a></span><span class="hspace"> </span><span class="RktSym">src</span><span class="hspace"> </span><span class="RktSym">port</span><span class="hspace"> </span><span class="RktVal">#f</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym">make-delims-table</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktSym">src</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="let.html#%28form._%28%28quote._~23~25kernel%29._let-values%29%29" class="RktStxLink" data-pltdoc="x">let-values</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktPn">(</span><span class="RktSym">l</span><span class="hspace"> </span><span class="RktSym">c</span><span class="hspace"> </span><span class="RktSym">p</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="linecol.html#%28def._%28%28quote._~23~25kernel%29._port-next-location%29%29" class="RktValLink" data-pltdoc="x">port-next-location</a></span><span class="hspace"> </span><span class="RktSym">port</span><span class="RktPn">)</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="pairs.html#%28def._%28%28quote._~23~25kernel%29._list%29%29" class="RktValLink" data-pltdoc="x">list</a></span><span class="hspace"> </span><span class="RktSym">src</span><span class="hspace"> </span><span class="RktSym">line</span><span class="hspace"> </span><span class="RktSym">col</span><span class="hspace"> </span><span class="RktSym">pos</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="if.html#%28form._%28%28lib._racket%2Fprivate%2Fletstx-scheme..rkt%29._and%29%29" class="RktStxLink" data-pltdoc="x">and</a></span><span class="hspace"> </span><span class="RktSym">pos</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="generic-numbers.html#%28def._%28%28quote._~23~25kernel%29._-%29%29" class="RktValLink" data-pltdoc="x"><span class="nobreak">-</span></a></span><span class="hspace"> </span><span class="RktSym">p</span><span class="hspace"> </span><span class="RktSym">pos</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">]</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></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="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">tuple-readtable</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="readtables.html#%28def._%28%28quote._~23~25kernel%29._make-readtable%29%29" class="RktValLink" data-pltdoc="x">make-readtable</a></span><span class="hspace"> </span><span class="RktVal">#f</span><span class="hspace"> </span><span class="RktVal">#\<</span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">terminating-macro</span><span class="hspace"> </span><span class="RktSym">parse-open-tuple</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></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="parameters.html#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._current-readtable%29%29" class="RktValLink" data-pltdoc="x">current-readtable</a></span><span class="hspace"> </span><span class="RktSym">tuple-readtable</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="Reading.html#%28def._%28%28quote._~23~25kernel%29._read%29%29" class="RktValLink" data-pltdoc="x">read</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._open-input-string%29%29" class="RktValLink" data-pltdoc="x">open-input-string</a></span><span class="hspace"> </span><span class="RktVal">"<1 , 2 , \"a\">"</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'(make-tuple (list 1 2 "a"))</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="parameters.html#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._current-readtable%29%29" class="RktValLink" data-pltdoc="x">current-readtable</a></span><span class="hspace"> </span><span class="RktSym">tuple-readtable</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="Reading.html#%28def._%28%28quote._~23~25kernel%29._read%29%29" class="RktValLink" data-pltdoc="x">read</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._open-input-string%29%29" class="RktValLink" data-pltdoc="x">open-input-string</a></span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktVal">"< #||# 1 #||# , #||# 2 #||# , #||# \"a\" #||# >"</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'(make-tuple (list 1 2 "a"))</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="define.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._define%29%29" class="RktStxLink" data-pltdoc="x">define</a></span><span class="hspace"> </span><span class="RktSym">tuple-readtable+</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="readtables.html#%28def._%28%28quote._~23~25kernel%29._make-readtable%29%29" class="RktValLink" data-pltdoc="x">make-readtable</a></span><span class="hspace"> </span><span class="RktSym">tuple-readtable</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktVal">#\*</span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">terminating-macro</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="lambda.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._lambda%29%29" class="RktStxLink" data-pltdoc="x">lambda</a></span><span class="hspace"> </span><span class="RktSym">a</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="special-comments.html#%28def._%28%28quote._~23~25kernel%29._make-special-comment%29%29" class="RktValLink" data-pltdoc="x">make-special-comment</a></span><span class="hspace"> </span><span class="RktVal">#f</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace"> </span><span class="hspace"> </span><span class="RktVal">#\_</span><span class="hspace"> </span><span class="RktVal">#\space</span><span class="hspace"> </span><span class="RktVal">#f</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></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="parameters.html#%28form._%28%28lib._racket%2Fprivate%2Fmore-scheme..rkt%29._parameterize%29%29" class="RktStxLink" data-pltdoc="x">parameterize</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym"><a href="Reading.html#%28def._%28%28quote._~23~25kernel%29._current-readtable%29%29" class="RktValLink" data-pltdoc="x">current-readtable</a></span><span class="hspace"> </span><span class="RktSym">tuple-readtable+</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="Reading.html#%28def._%28%28quote._~23~25kernel%29._read%29%29" class="RktValLink" data-pltdoc="x">read</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="stringport.html#%28def._%28%28quote._~23~25kernel%29._open-input-string%29%29" class="RktValLink" data-pltdoc="x">open-input-string</a></span><span class="hspace"> </span><span class="RktVal">"< * 1 __,__</span><span class="hspace"> </span><span class="RktVal">2 __,__ * \"a\" * >"</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'(make-tuple (list 1 2 "a"))</span></p></td></tr></table></blockquote></div></p><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", 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