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<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"/><title>6 Len</title><link rel="stylesheet" type="text/css" href="scribble.css" title="default"/><link rel="stylesheet" type="text/css" href="racket.css" title="default"/><link rel="stylesheet" type="text/css" href="manual-style.css" title="default"/><link rel="stylesheet" type="text/css" href="manual-racket.css" title="default"/><script type="text/javascript" src="scribble-common.js"></script><script type="text/javascript" src="manual-racket.js"></script><!--[if IE 6]><style type="text/css">.SIEHidden { overflow: hidden; }</style><![endif]--></head><body id="scribble-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">Sugar:<span class="mywbr"> </span> readability & convenience library</a></td></tr></table></div><div class="tocviewsublistonly" style="display: block;" id="tocview_0"><table cellspacing="0" cellpadding="0"><tr><td align="right">1 </td><td><a href="Installation___updates.html" class="tocviewlink" data-pltdoc="x">Installation & updates</a></td></tr><tr><td align="right">2 </td><td><a href="Coercion.html" class="tocviewlink" data-pltdoc="x">Coercion</a></td></tr><tr><td align="right">3 </td><td><a href="Container.html" class="tocviewlink" data-pltdoc="x">Container</a></td></tr><tr><td align="right">4 </td><td><a href="Debug.html" class="tocviewlink" data-pltdoc="x">Debug</a></td></tr><tr><td align="right">5 </td><td><a href="File.html" class="tocviewlink" data-pltdoc="x">File</a></td></tr><tr><td align="right">6 </td><td><a href="Len.html" class="tocviewselflink" data-pltdoc="x">Len</a></td></tr><tr><td align="right">7 </td><td><a href="License___source_code.html" class="tocviewlink" data-pltdoc="x">License & source code</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><div class="tocsub"><div class="tocsubtitle">On this page:</div><table class="tocsublist" cellspacing="0"><tr><td><a href="#%28def._%28%28lib._sugar%2Flen..rkt%29._len%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">len</span></span></a></td></tr></table></div></div><div class="maincolumn"><div class="main"><div class="versionbox"><span class="version">6.0.1.13</span></div><div class="navsettop"><span class="navleft"><div class="nosearchform"></div> </span><span class="navright"> <a href="File.html" title="backward to "5 File"" data-pltdoc="x">← prev</a> <a href="index.html" title="up to "Sugar: readability & convenience library"" data-pltdoc="x">up</a> <a href="License___source_code.html" title="forward to "7 License & source code"" data-pltdoc="x">next →</a></span> </div><h3>6<tt> </tt><a name="(part._.Len)"></a><a name="(mod-path._sugar/len)"></a>Len</h3><p><table cellspacing="0" cellpadding="0" class="defmodule"><tr><td align="left"><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/require.html#%28form._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._require%29%29" class="RktStxLink" data-pltdoc="x">require</a></span><span class="stt"> </span><a href="Len.html" class="RktModLink" data-pltdoc="x"><span class="RktSym">sugar/len</span></a><span class="RktPn">)</span></td><td align="right"><span class="RpackageSpec"><span class="Smaller"> package:</span> <span class="stt">sugar</span></span></td></tr></table></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._((lib._sugar/len..rkt)._len))"></a><span title="Provided from: sugar/len | Package: sugar"><span class="RktSym"><a href="Len.html#%28def._%28%28lib._sugar%2Flen..rkt%29._len%29%29" class="RktValDef RktValLink" data-pltdoc="x">len</a></span></span><span class="hspace"> </span><span class="RktVar">x</span><span class="RktPn">)</span><span class="hspace"> </span>→<span class="hspace"> </span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/number-types.html#%28def._%28%28quote._~23~25kernel%29._integer~3f%29%29" class="RktValLink" data-pltdoc="x">integer?</a></span></p></blockquote></td></tr><tr><td><span class="hspace"> </span><span class="RktVar">x</span><span class="hspace"> </span>:<span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/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="http://docs.racket-lang.org/reference/pairs.html#%28def._%28%28quote._~23~25kernel%29._list~3f%29%29" class="RktValLink" data-pltdoc="x">list?</a></span><span class="hspace"> </span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/vectors.html#%28def._%28%28quote._~23~25kernel%29._vector~3f%29%29" class="RktValLink" data-pltdoc="x">vector?</a></span><span class="hspace"> </span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/sets.html#%28def._%28%28lib._racket%2Fset..rkt%29._set~3f%29%29" class="RktValLink" data-pltdoc="x">set?</a></span><span class="hspace"> </span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/strings.html#%28def._%28%28quote._~23~25kernel%29._string~3f%29%29" class="RktValLink" data-pltdoc="x">string?</a></span><span class="hspace"> </span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/symbols.html#%28def._%28%28quote._~23~25kernel%29._symbol~3f%29%29" class="RktValLink" data-pltdoc="x">symbol?</a></span><span class="hspace"> </span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/Manipulating_Paths.html#%28def._%28%28quote._~23~25kernel%29._path~3f%29%29" class="RktValLink" data-pltdoc="x">path?</a></span><span class="hspace"> </span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/hashtables.html#%28def._%28%28quote._~23~25kernel%29._hash~3f%29%29" class="RktValLink" data-pltdoc="x">hash?</a></span><span class="RktPn">)</span></td></tr></table></blockquote></div><div class="SIntrapara">Calculate the length of <span class="RktVar">x</span> in the least surprising way possible, or if it can’t be done, raise an error. Named in honor of the original discover of the length-reticulation algorithm, Prof. Leonard Spottiswoode.</div></p><p><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><p>Examples:</p></td></tr><tr><td><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="Len.html#%28def._%28%28lib._sugar%2Flen..rkt%29._len%29%29" class="RktValLink" data-pltdoc="x">len</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">(</span><span class="RktVal">a</span><span class="hspace"> </span><span class="RktVal">b</span><span class="hspace"> </span><span class="RktVal">c</span><span class="RktVal">)</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">3</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="Len.html#%28def._%28%28lib._sugar%2Flen..rkt%29._len%29%29" class="RktValLink" data-pltdoc="x">len</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/vectors.html#%28def._%28%28quote._~23~25kernel%29._list-~3evector%29%29" class="RktValLink" data-pltdoc="x">list->vector</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">(</span><span class="RktVal">a</span><span class="hspace"> </span><span class="RktVal">b</span><span class="hspace"> </span><span class="RktVal">c</span><span class="RktVal">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">3</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="Len.html#%28def._%28%28lib._sugar%2Flen..rkt%29._len%29%29" class="RktValLink" data-pltdoc="x">len</a></span><span class="hspace"> </span><span class="RktVal">'</span><span class="RktVal">abc</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">3</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="Len.html#%28def._%28%28lib._sugar%2Flen..rkt%29._len%29%29" class="RktValLink" data-pltdoc="x">len</a></span><span class="hspace"> </span><span class="RktVal">"abc"</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">3</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="Len.html#%28def._%28%28lib._sugar%2Flen..rkt%29._len%29%29" class="RktValLink" data-pltdoc="x">len</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/Manipulating_Paths.html#%28def._%28%28quote._~23~25kernel%29._string-~3epath%29%29" class="RktValLink" data-pltdoc="x">string->path</a></span><span class="hspace"> </span><span class="RktVal">"abc"</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">3</span></p></td></tr><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="Len.html#%28def._%28%28lib._sugar%2Flen..rkt%29._len%29%29" class="RktValLink" data-pltdoc="x">len</a></span><span class="hspace"> </span><span class="RktPn">(</span><span class="RktSym"><a href="http://docs.racket-lang.org/reference/hashtables.html#%28def._%28%28quote._~23~25kernel%29._make-hash%29%29" class="RktValLink" data-pltdoc="x">make-hash</a></span><span class="hspace"> </span><span class="RktVal">`</span><span class="RktVal">(</span><span class="RktVal">(</span><span class="RktVal">a</span><span class="hspace"> </span><span class="RktVal">. </span><span class="RktVal">1</span><span class="RktVal">)</span><span class="RktVal">(</span><span class="RktVal">b</span><span class="hspace"> </span><span class="RktVal">. </span><span class="RktVal">2</span><span class="RktVal">)</span><span class="RktVal">(</span><span class="RktVal">c</span><span class="hspace"> </span><span class="RktVal">. </span><span class="RktVal">3</span><span class="RktVal">)</span><span class="RktVal">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktRes">3</span></p></td></tr></table></blockquote></td></tr></table></p><p>Perhaps ironically, positive integers do not have a length.</p><p><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><p>Example:</p></td></tr><tr><td><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">> </span><span class="RktPn">(</span><span class="RktSym"><a href="Len.html#%28def._%28%28lib._sugar%2Flen..rkt%29._len%29%29" class="RktValLink" data-pltdoc="x">len</a></span><span class="hspace"> </span><span class="RktVal">3</span><span class="RktPn">)</span></td></tr><tr><td><p><span class="RktErr">len: can’t calculate length of 3</span></p></td></tr></table></blockquote></td></tr></table></p><div class="navsetbottom"><span class="navleft"><div class="nosearchform"></div> </span><span class="navright"> <a href="File.html" title="backward to "5 File"" data-pltdoc="x">← prev</a> <a href="index.html" title="up to "Sugar: readability & convenience library"" data-pltdoc="x">up</a> <a href="License___source_code.html" title="forward to "7 License & source code"" data-pltdoc="x">next →</a></span> </div></div></div><div id="contextindicator"> </div></body></html> |