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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>4 </td><td><a href="scheme-forms.html" class="tocviewlink" data-pltdoc="x">Expressions and Definitions</a></td></tr></table><div class="tocviewsublistbottom" style="display: block;" id="tocview_1"><table cellspacing="0" cellpadding="0"><tr><td align="right">4.1 </td><td><a href="" class="tocviewselflink" data-pltdoc="x">Notation</a></td></tr><tr><td align="right">4.2 </td><td><a href="binding.html" class="tocviewlink" data-pltdoc="x">Identifiers and Binding</a></td></tr><tr><td align="right">4.3 </td><td><a href="application.html" class="tocviewlink" data-pltdoc="x">Function Calls (Procedure Applications)</a></td></tr><tr><td align="right">4.4 </td><td><a href="lambda.html" class="tocviewlink" data-pltdoc="x">Functions (Procedures):<span class="mywbr"> </span> <span class="RktSym"><span class="RktStxLink">lambda</span></span></a></td></tr><tr><td align="right">4.5 </td><td><a href="define.html" class="tocviewlink" data-pltdoc="x">Definitions:<span class="mywbr"> </span> <span class="RktSym"><span class="RktStxLink">define</span></span></a></td></tr><tr><td align="right">4.6 </td><td><a href="let.html" class="tocviewlink" data-pltdoc="x">Local Binding</a></td></tr><tr><td align="right">4.7 </td><td><a href="conditionals.html" class="tocviewlink" data-pltdoc="x">Conditionals</a></td></tr><tr><td align="right">4.8 </td><td><a href="begin.html" class="tocviewlink" data-pltdoc="x">Sequencing</a></td></tr><tr><td align="right">4.9 </td><td><a href="set_.html" class="tocviewlink" data-pltdoc="x">Assignment:<span class="mywbr"> </span> <span class="RktSym"><span class="RktStxLink">set!</span></span></a></td></tr><tr><td align="right">4.10 </td><td><a href="quote.html" class="tocviewlink" data-pltdoc="x">Quoting:<span class="mywbr"> </span> <span class="RktSym"><span class="RktStxLink">quote</span></span> and <span class="RktVal">'</span></a></td></tr><tr><td align="right">4.11 </td><td><a href="qq.html" class="tocviewlink" data-pltdoc="x">Quasiquoting:<span class="mywbr"> </span> <span class="RktSym"><span class="RktStxLink">quasiquote</span></span> and <span class="RktVal">‘</span></a></td></tr><tr><td align="right">4.12 </td><td><a href="case.html" class="tocviewlink" data-pltdoc="x">Simple Dispatch:<span class="mywbr"> </span> <span class="RktSym"><span class="RktStxLink">case</span></span></a></td></tr><tr><td align="right">4.13 </td><td><a href="parameterize.html" class="tocviewlink" data-pltdoc="x">Dynamic Binding:<span class="mywbr"> </span> <span class="RktSym"><span class="RktStxLink">parameterize</span></span></a></td></tr></table></div></div></div></div><div class="maincolumn"><div class="main"><div class="navsettop"><span class="navleft"><form class="searchform"><input class="searchbox" style="color: #888;" type="text" value="...search manuals..." title="Enter a search string to search the manuals" onkeypress="return DoSearchKey(event, this, "6.1", "../");" onfocus="this.style.color="black"; this.style.textAlign="left"; if (this.value == "...search manuals...") this.value="";" onblur="if (this.value.match(/^ *$/)) { this.style.color="#888"; this.style.textAlign="center"; this.value="...search manuals..."; }"/></form> <a href="../index.html" title="up to the documentation top" data-pltdoc="x" onclick="return GotoPLTRoot("6.1");">top</a></span><span class="navright"> <a href="scheme-forms.html" title="backward to "4 Expressions and Definitions"" data-pltdoc="x">← prev</a> <a href="scheme-forms.html" title="up to "4 Expressions and Definitions"" data-pltdoc="x">up</a> <a href="binding.html" title="forward to "4.2 Identifiers and Binding"" data-pltdoc="x">next →</a></span> </div><h4 x-source-module="(lib "scribblings/guide/guide.scrbl")" x-part-tag=""syntax-notation"">4.1<tt> </tt><a name="(part._syntax-notation)"></a>Notation</h4><p>This chapter (and the rest of the documentation) uses a slightly
different notation than the character-based grammars of the
<a href="to-scheme.html" data-pltdoc="x">Racket Essentials</a> chapter. The grammar for a use of a syntactic
form <span class="RktKw">something</span> is shown like this:</p><blockquote class="leftindent"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><span class="RktPn">(</span><span class="RktKw">something</span><span class="hspace"> </span><span class="RktPn">[</span><span class="RktVar">id</span><span class="hspace"> </span><span class="RktMeta">...+</span><span class="RktPn">]</span><span class="hspace"> </span><span class="RktVar">an-expr</span><span class="hspace"> </span><span class="RktMeta">...</span><span class="RktPn">)</span></td></tr></table></blockquote></blockquote><p>The italicized meta-variables in this specification, such as
<span class="RktVar">id</span> and <span class="RktVar">an-expr</span>, use the syntax of Racket
identifiers, so <span class="RktVar">an-expr</span> is one meta-variable. A naming
convention implicitly defines the meaning of many meta-variables:</p><ul><li><p>A meta-variable that ends in <span class="RktVar">id</span> stands for an
identifier, such as <span class="RktSym">x</span> or
<span class="RktSym">my-favorite-martian</span>.</p></li><li><p>A meta-identifier that ends in <span class="RktVar">keyword</span> stands
for a keyword, such as <span class="RktPn">#:tag</span>.</p></li><li><p>A meta-identifier that ends with <span class="RktVar">expr</span> stands for any
sub-form, and it will be parsed as an expression.</p></li><li><p>A meta-identifier that ends with <span class="RktVar">body</span> stands for any
sub-form; it will be parsed as either a local definition or an
expression. A <span class="RktVar">body</span> can parse as a definition only if
it is not preceded by any expression, and the last
<span class="RktVar">body</span> must be an expression; see also <a href="define.html#%28part._intdefs%29" data-pltdoc="x">Internal Definitions</a>.</p></li></ul><p>Square brackets in the grammar indicate a parenthesized sequence of
forms, where square brackets are normally used (by convention). That
is, square brackets <span style="font-style: italic">do not</span> mean optional parts of the
syntactic form.</p><p>A <span class="RktMeta">...</span> indicates zero or more repetitions of the
preceding form, and <span class="RktMeta">...+</span> indicates one or more
repetitions of the preceding datum. Otherwise, non-italicized
identifiers stand for themselves.</p><p>Based on the above grammar, then, here are a few conforming uses of
<span class="RktKw">something</span>:</p><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktKw">something</span><span class="hspace"> </span><span class="RktPn">[</span><span class="RktSym">x</span><span class="RktPn">]</span><span class="RktPn">)</span></td></tr><tr><td><span class="RktPn">(</span><span class="RktKw">something</span><span class="hspace"> </span><span class="RktPn">[</span><span class="RktSym">x</span><span class="RktPn">]</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&rel=generic-numbers.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._%252B%2529%2529&version=6.1" class="RktValLink Sq" data-pltdoc="x">+</a></span><span class="hspace"> </span><span class="RktVal">1</span><span class="hspace"> </span><span class="RktVal">2</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="RktPn">(</span><span class="RktKw">something</span><span class="hspace"> </span><span class="RktPn">[</span><span class="RktSym">x</span><span class="hspace"> </span><span class="RktSym">my-favorite-martian</span><span class="hspace"> </span><span class="RktSym">x</span><span class="RktPn">]</span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://download.racket-lang.org/docs/6.1/html/local-redirect/index.html?doc=reference&rel=generic-numbers.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._%252B%2529%2529&version=6.1" class="RktValLink Sq" data-pltdoc="x">+</a></span><span class="hspace"> </span><span class="RktVal">1</span><span class="hspace"> </span><span class="RktVal">2</span><span class="RktPn">)</span><span class="hspace"> </span><span class="RktVal">#f</span><span class="RktPn">)</span></td></tr></table></blockquote><p>Some syntactic-form specifications refer to meta-variables that are
not implicitly defined and not previously defined. Such meta-variables
are defined after the main form, using a BNF-like format for
alternatives:</p><blockquote class="leftindent"><blockquote class="SVInsetFlow"><table cellspacing="0" cellpadding="0" class="boxed RBoxed"><tr><td><span class="RktPn">(</span><span class="RktKw">something-else</span><span class="hspace"> </span><span class="RktPn">[</span><span class="RktVar">thing</span><span class="hspace"> </span><span class="RktMeta">...+</span><span class="RktPn">]</span><span class="hspace"> </span><span class="RktVar">an-expr</span><span class="hspace"> </span><span class="RktMeta">...</span><span class="RktPn">)</span></td></tr><tr><td><span class="stt"> </span></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="specgrammar"><tr><td align="right" valign="baseline"><span class="RktVar">thing</span></td><td align="left" valign="baseline"><span class="stt"> </span></td><td align="center" valign="baseline">=</td><td align="left" valign="baseline"><span class="stt"> </span></td><td align="left" valign="baseline"><span class="RktVar">thing-id</span></td></tr><tr><td align="right" valign="baseline"><span class="stt"> </span></td><td align="left" valign="baseline"><span class="stt"> </span></td><td align="center" valign="baseline">|</td><td align="left" valign="baseline"><span class="stt"> </span></td><td align="left" valign="baseline"><span class="RktVar">thing-keyword</span></td></tr></table></td></tr></table></blockquote></blockquote><p>The above example says that, within a <span class="RktKw">something-else</span>
form, a <span class="RktVar">thing</span> is either an identifier or a keyword.</p><div class="navsetbottom"><span class="navleft"><form class="searchform"><input class="searchbox" style="color: #888;" type="text" value="...search manuals..." title="Enter a search string to search the manuals" onkeypress="return DoSearchKey(event, this, "6.1", "../");" onfocus="this.style.color="black"; this.style.textAlign="left"; if (this.value == "...search manuals...") this.value="";" onblur="if (this.value.match(/^ *$/)) { this.style.color="#888"; this.style.textAlign="center"; this.value="...search manuals..."; }"/></form> <a href="../index.html" title="up to the documentation top" data-pltdoc="x" onclick="return GotoPLTRoot("6.1");">top</a></span><span class="navright"> <a href="scheme-forms.html" title="backward to "4 Expressions and Definitions"" data-pltdoc="x">← prev</a> <a href="scheme-forms.html" title="up to "4 Expressions and Definitions"" data-pltdoc="x">up</a> <a href="binding.html" title="forward to "4.2 Identifiers and Binding"" data-pltdoc="x">next →</a></span> </div></div></div><div id="contextindicator"> </div></body></html>
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