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<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" http:/wwworg/html1strict <html xmlns="http://www.w3.org/ <head> <script type="text/javascript" src://cdn.netnpm@2.?configTeX-AMS-MML_HTMLorMML" </script> <title>GAP (ref) - <eta-equiv=content" content="text;charset=UTF-"/ <meta> <link type"/javascript" <manualtype=text"<script <script type="text/javascript">overwriteStyle();</script> </ead <body ="chap4" ="jscontent()> <div rel=stylesheet="textcss ="manual.css <script src=manual" type"text/javascript"<script <p id="mathjaxlink" class> <p><a id="X7FE7C0C17E1ED118" name="X7FE7C0C17E1ED118"></a></p> <div class="ChapSects"><a href="chap4_mj.html#X7FE7C0C17E1ED118">4 <span class="Heading">T <div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap4_mj.html </span> </div> <div class="ContSect"><span class="tocline"><span class="nocss"> </body ="chap4 onload"jscont </pan> </div> <div class="ContSect"><span java.lang.StringIndexOutOfBoundsException: Index 0 out of </span> </div> <div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap4_mj.html <span> </div ="ChapSects>ahref".#X7FE7C0C17E1ED1184 < class"TheProgramming <span</ <div"html"41 span"Language Overview/></> </span> </div> <div class="ContSect"/> <span <div class="ContSSBlock/> < classContSS />spanclass""> <span ="chap4_mjhtmlX85CF993B7D19F2C4">46-1 IsValidIdent <<> </> </div>div <div class="ContSect">div="ContSect>spanclass"oclineclassnocss>nbspspanhref.htmlX7C53 </span> </div> <div class="ContSect"><span class="tocline<span> </pan <div class="ContSSBlock"> <span class""><span class=tocline"spanclass""&;</>ahref=chap4_mj.html#X860313A179A5163F">4 <span class="spanclass"ontSS<br/<span ="nocss">nbsp;/>a =chap4_mj#X85CF993B7D19F2C4"46- I </><div <div class"< =tocline">< classnocssnbspspan>a href=chap4_mj#X816FBEEA85782EC2">.9 <pan class" </span> <divclass"java.lang.StringIndexOutOfBoundsException: Index 25 out of bounds for l <span="ContSS"><br>span ="nocss"&;nbsp> =chap4_mj#7CD3523B84744EB249-1 IsReadOnlyGlobal/>sp <span class="ContSS"><br /><span class="nocss"> </span><a href="chap4_mj.html#X850CE44478254F2 <span class="ContSS"><br /><span class="nocss"> </span><a <span class="ContSS"><br /><span class="nocss"> </span<div> <span classdiv class=ContSect<span class"tocline"><spanclassnocss>nbspspan><a href=chap4_mj < classContSS /< class"ocss>nbsp&;</span<a ="chap4_mj#X823D4BC378395B32">49-IsBoundGlobal</a>/ <span class="ContSS"><br /><span class="<panclass="ContSSbr/< =nocss;nbsp>a hrefchap4_mj.html <"ContSS"><br /<span="nocss"nbsp;span =chap4_mj#X7D39D3E17CF49F5B>.- BindGlobal>/pan <spandiv ="ContSect>spanclass""< =nocss>nbsp<span< =chap4_mjhtmlX816FBEEA85782EC2">49< class <span class="ContSS"><br /><span class> < classContSSbr >span="">&; /><a ="chap4_mj.tmlX870169447AF490D8">4.11 NamesUserGVarsa<span </div></div> <div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap4_mj.html </span </div> <div class="ContSect"><span class="tocline"><span class="nocss<span class="ContSS><br /<spancl <span </div> <div class="ContSect"><span class="tocline"><span classspanclass"<br >spanclass"ocssnbsp;/p </> <div class="ContSSBlock"> <span="ontSS><br/<span class=nocss">&bsp;</span href"chap4_mj.html#X80B93A9C7E0A57F4">4121 span </span> <span class="ContSS"><br /><span class="nocss"> </span><a href="chap4_mj.html#X867D54987EF86D1 </span> </div></div> <div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap4_mj.html </span> </div> <div class="ContSect"><span class="tocline"><span class="nocss"> </spandiv>/div </span </div> <div class="ContSect"><span class/pan <span <div class < ="toclinespan=";>< =".#78C70489791FDF43. spanclass""Function Calls<span<a> </span=" < class >span="nocss">; ><ahref=chap4_mjX80B93A9C7E0A57F4.- span class"">Function WithArg </span> <span class="ContSS"><br /><span class="nocss"> </span><a href="chap4_mj.html#X875000188622700 </span> <span class="ContSS"><br /><span class/> <java.lang.StringIndexOutOfBoundsException: Index 7 out of bounds for length 7 <span class="ContSS"><br /><span class="nocss"> </span><a href="chap4_mj.html#X8295CBF47FAA05C </span> <span class="ContSS"><br /><span class="nocss"> </span><a href="chap4_mj.html#X78783E777867638 </span> <span="ContSS"><br>span="nocss>nbsp&;/>a href="hap4_mjX7B60C6127E183021"4157< class=Heading </pan <spanspan ="ContSS">< >span="nocss">nbsp&;</><a href=chap4_mjhtml">415-< class=""> Calls/>/> </span <span class="ContSS"/span> <span </div></div/> < classContSect"><span class="tocline<spanclassnocss&bspspanahrefch </span> <div class="ContSSBlock"> <span class"ContSS"><br /><spanclass="nocss" <spana href href"chap4_mj.html#X81558D6681 </div></div> <div <h34 <span classHeading> ProgrammingLanguage<span/h3> <p>hischapter <strong=pkg"GAP<strong programming language.It ,inprinciple to predict result <p>a ="X7B5FF6827DFBDF20name"X7B5FF6827DFBDF20<a<p <h4>4.1 <s=ContSS />span class>nbsp;nbspspan< href=".html#X812C6ABC7A182E9E">4.- < class"Retur <p>First we> this isand that not externalrepresentations according therules below, as. Those are called e <p>The internal representation created by reading is called either an <em>expression</em> or a <em>st <p>After the input has been read it/><div <p <p>The process called>printing<em.It takesthe produced the and an external representationi.. a <p>Lets look <div="">pre 1 + 2 *<The internal representationcreated reading called an<em>expression</em> or a <em>statement< </></div <p><strongjava.lang.StringIndexOutOfBoundsException: Index 0 out of bounds for leng <div class="example"><pre> + / \ 1 \ 2 3 < <p>Thisdiv class=examplepre> <> this fashion we can predictthe of input weknow the syntactic that governtheprocess of reading <p><a id="X80A85A707B6F4BE7" name="X80A85A707B6F4BE7"></a></p> <h4>4.2 <span class="Heading">Lexical Structure</span></h4> <p>Most input of <strong class="pkg">GAP</strong> consists of sequences of thep>n thisfashion we ca <p>Digits, uppercase and lowercase letters, <strong class="button">Space</strong>, <strong clas <div class="example"><pre " ' * + , -# ./:;; = &; ~ [ \ ] ^ _ { } ! </pre></div> java.lang.StringIndexOutOfBoundsException: Index 0 out of bounds for length 0 <p><a id="X7E90E6607F4E4943" name="X7E90E6607F4E4943"></a></p> <h4>4.3 <span class="Heading">Symbols</span></h4> <p>The process of reading, i.e., of assembling the input into ()*+ # <p>A <em>keyword</em> is } <p>Operator <>. <span class="eading>Symbols</span<h4 + java.lang.StringIndexOutOfBoundsException: Index 0 out of bounds for length 0 > gt! := . .. -> , ; [ ] { } : </pre></div> <p>Note <p><a divclass="example"<> <h4>4. &t;> < <= > >= ![ <p>The{} () : <p>A <em>comment</em> starts with the character <code class="code">#</code>, which is sometimes calle <p>For example, the following statement</p> <div class="example"><pre">Whitespaces/></h4> iflt0 then a:ielse=ifi </pre></div> <p>is equivalent to</p> <div class="example f i :;# takeadditivejava.lang.StringIndexOutOfBoundsException: Index 45 out of bounds else =i takeitself fi pre <p>a: ;# itself </re/> ifi<0thena:p>which the shows it possible write comments the statementis<emnot<em top> </pre></div> <psince the <code class=keywif<code beseparated from the identifier< class"i/ode a whitespace a <p><a java.lang.StringIndexOutOfBoundsException: Index 0 out of bounds for length 0 <h4>4.5 <span class="Heading">Keywords</span></h4 <p><em>Keywords</ <div <span class="GAPprompt">gap></span> <span class="GAPinput">keys:=SortedList( GAPInfo.Keywor <span="GAPprompt>></pan><span class"GAPinputarr List( 0 .. ( l/4 )1 ] i-gt{ 4* + 1. 4 ]});/span> <spanclass=GAPprompt>/span>span="GAPinput">if lmod 4<gt0then Add ar <span="GAPprompt>&;/> <pan class""Lengthkeys) PrintArray( )/> 35 [ [ Assert, Info, IsBound, QUIT ], [TryNextMethod,Unbindandatomic [ break, continue, do, elif ], [ else, falsefi] [ for, function, if, in ], [ local, mod, not, od ], [ or, quit, readonly, readwrite ], [ rec, repeat, return, then ], [ true, until, while ] ] </pre></div> <p>Note that (almost) all keywords are written in lowercase and that they are case sensitive. For <p><em>Note</em>: Several tokens from , repeatreturn, then ] <p>Keywords <code class="code">atomic</code>, <<pre<> <p>a id=X860313A179A5163F" ="X860313A179A5163F"></a>/p> <h4p>emNote</em>: Several tokensfrom the list of keywords above appear tobe identifiersreprese <p>An <em>identifier</em> is used to refer to a variable (see <a href="chap4_mj.html#X7A4C2D0E7E28 < <div class="example"><pre> a foo ello HELLO x100 100x _100pAn>identifier</m> isused to toa variable ( <a href=chap4_mj.html#X7A4C2D0E7E28 some_people_prefer_underscores_to_separate_wordsHello WePreferMixedCaseToSeparateWords abc </presome_people_prefer_underscores_to_separate_words <p>Note@def <p>The <div class G<> backslashcodeclass=code"\/> can be used to include other characters identifiers;abacksla </(\,5) p identifier a functioncode=code><code>/> <p>An identifier that starts with a <p>The < <h5>4<><a id"85CF993B7D19F2C4" nameX85CF993B7D19F2C4"></a></p> <div class="func"><table class="func" width="100%"><tr><td class="tdleft"><code class="func">&# g <varclass="Arg">str> would a valididentifier of, digits underscores;otherwiseit returns < cl <p>Note that the <q>at</q>-character is used to implement namespaces for global variables in packag <p><a id="X839A7F8E84BBCA57" name="X839A7F8E84BBCA57"></a></p> <h5>4.6-2 <span class="Heading">Conventions about Identifiers</span></h5> <p>(The following rule is stated also in Section <a href="../../doc/tut/chap2_mj< <p>The name of almost every global variable <p>For example, valid classpkg</strong which some variables names withcapital lettersmay runi <p><a id>The rule stated inSection <ahref=./.docchap2_mj#X82F47EA88347AC2D< classRefLink: Var <h4>4.7 <span class="Heading">Expressions<>The nameof every global in thestrong="pkg">GAP</stro <p>An <em>expression</em> is a construct that evaluates to a value. Syntactic constructs that are ex <p>Note that an expression is not the same as a value. For <p>The simplest cases <ul> <li><p>variables ( </li <><> literals Section<ahref.#815F71EA7BC0EB6Fspan4./><>/ </li> <li><p><li> </li/> <><pintegerliterals( Chapterahref=chap14_mj#X853DF11B80068ED5< classRefLink>4<span<a)<pjav </li <lipfloatingpoint ( Chapter<a href"chap19_mj.#X81AA901181CA568F"><spanclass"19span<a>,/> </li><p> point (seeChapterhref.#AA901181CA568F class"/><>,/> <li><p>permutation literals (see Chapter <a href="chap42_mj.html#X80F808307A2D5AB8"><span cla </li> <li><p>string < <li <li <li><p>list literalsli </li> <li<>ecord (see <a href=chap29_mjX7AA1073C7E943DD7< classRefLink<span></a)</ </li> </ul, for the expressions abovecanbe combined the to more expressionsOf course those expressi <p>Expressions, for="">-to<td <pThe example a verysimple value4 a more expression/> <div class"">left-right<td <span class="GAPprompt"tr 4 <span class="GAPprompt">gap></span> <span class="GAPinput">2 * 2 + 9 = Fibonacci(7) and Fibonacci( true </pre></div> <p>The followingtr <div class="tdleft"><m>comparison(ee a ="chap4_mj.html#X7A274A1F8553B7E6">span="">413<span>< <> <td class="tdleft"><em>operator</em <td class="tdleft"><em>associativity</em></td> </td ="tdleft> <ode class=code"=/>,<code=code>lt;</code>,<codeclass"ode><</code;</code> <code class" <tr> <td="tdleft>em>rithmetic (see ahref"chap4_mjX7B66C8707B5DE10A><span="RefLink">414/></a)/></t <td class="tdlefttdclass"tdleft">/td> </tr> <tr> < class"> <code class"code"^</ode</djava.lang.StringIndexOutOfBoundsException: Index 55 <td class="tdleft">none</td> </tr> <tr <td class="tdleft"> unary <code class="code">+</tdclass"tdleft"">left-to-right</td> <td classtdleftright-toleft</d </tr> <tr <td class">eftto-ight<td> <td class="tdleft">left> </tr><br > <> <td <tdclass="">left-right> </tr> <trh4>4.8< class"">Variables></h4java.lang.StringIndexOutOfBoundsException: Index 51 ou <td class=tdleftemcomparisonsee href.htmlX7A274A1F8553B7E6">span class="RefLink"413</p <td class="tdleft"></td> </tr> < <td class="tdleft"> <code is class <em>arguments/m>of. They similarly to variables, except theyar <td class="tdleft">none</td> </tr> <tr> <td class="tdleft"><em>logical (see <a href="chap20_mj.html#X79AD41A185FD7213"><span class=" <td class="tdleftend; </tr> <tr> <tdclass"tdleft> code class="">not/><td> <td </tr> <tr> <td class="tdleft"> <code class="keyw">and</code></td> <td class="tdleft">left-to-right</td> /> <java.lang.StringIndexOutOfBoundsException: Index 0 out of bounds for length 0 < classclassor/ <td class="tdleft">left-to-right</td> <> </table>4- IsBound> </div> <p< ="X7A4C2D0E7E286B4Fname"">a<p> <h44. < classHeading</span<h4 <p> <p>Initially an ordinary variable is not bound>482 Unbind/5> <p>A pdeletesthe < class"">ident>.If thereisno othervariable pointing thesamevalue <varclass=A <p>Each variablehasa thatis called itsemidentifier</em>.This isbecause a givenscope an identi <div class="example"><> vastmajority of <strong="pkg">GAP</> aredefinedat the outerlevel(he glob g := 0; # global variable g x : ( a,b c) local y; g := c; # c refers to argument c of functionCertain special areprovidedformanipulating variab = ) local d, e, f; d := y; # y refers to argument y of function y e := b; # b refers to argument b of function x f := g; # g refers to global variable div class="example"><pre> return d + e + f; end return y( a ); # y refers to span="GAPprompt">><spanspan="GAPinput">globalb : truespan> end </pre></div> <p>It is important class"gapgt</span> <spanclass""f :function)<> <p>In those languages a variable denotes a block of memory. The value of the variable is <span="GAP <p>In <strong class="pkg">GAP</strong> on the ="GAPprompt"&; span">return 2;<span <a="X842B89D4860FD5DB" name">/a<p> <h5>4.8-1 IsBound 3 +1; <div class="func"><table class="func"java.lang.StringIndexOutOfBoundsException: Index <p<codeclass"IsBound</code <code ="keywtrue> the< class">ident<var to avalue,and <code class"">fal <p>For records and lists <p> thatthefunctions class=func</code < ="chap4_mj.html#X876A6EB68745 <p><a id="><id"X7CD3523B84744EB2 name"><a><pjava.lang.StringIndexOutOfBoundsException: Inde <h5>4.8-2 Unbind <div class="func"><table =keywcodeif global bystring class</var read and ="">false otherwise de <p>deletes"CE44478254F27=X850CE44478254F27/a/java.lang.StringIndexOutOfBoundsExcep <p>For ="func">table""width%><>td"tdleft"><codeclass">#8227 </code> <var class="">name</var> )<td><td =" <p><a id=" <h4>4.9 <span class="java.lang.StringIndexOutOfBoundsException: Index 0 out of bounds <p>The vast h5>4.3MakeReadWriteGlobal<h5> <p>Note that for packages <in special facilitiesare provided for global which not for other types variable as variableso <p>First <span class="GAPprompt">gap>17 < class>>/> <spanclass"">globalbtrue;/span <span class="GAPprompt">gap <pan="GAPprompt>>span span class=""(globalb/> <span class="GAPprompt"gap;/spanspan""MakeReadOnlyGlobalxx"</pan> <spanclass">&;/>< ="APinput> :16<span <ss"APprompt"&;/> <span="GAPinput"> return globali+1;/spanjava.lang.StringIndexOutOfBound <span="GAPprompt">&t</span>< classGAPinput else<span> <span class="GAPprompt">></span> <span class="GAPinput"> return globali + 2;</span> <span class can; after making it writable tocontinue <class"">></> <span="GAPinput">nd;<span <span class=GAPprompt">&;/><spanclass"GAPinputIsReadOnlyGlobal"xx");<span function ( ) return3 +; end <prediv> <p>spanclass"gapgt<span>< ="APinput>("";/> <p>Note that the functions <code class="func"> <p><a id="X7CD3523B84744EB2" name="X7CD3523B84744EB2"></a></p> <>4.9- IsReadOnlyGlobal/> <div="func>tableclass"func="100%"<tr>td class"tdleft"><codeclass"‣ IsReadOnlyGlobal</> <p>returns <code class="keyw">true</code> if the global variable named by the string <var class="Ar <p><a id="X850CE44478254F27" name="X850CE44478254F27"></a></p> <h5>4.9-2 MakeReadOnlyGlobal</h5> <div class="func"><table <p>marks the globalvariable named by the string <varclass"Arg>name</var> read-only.</> <p><h5>4.- ValueGlobal</> <p><a div class"< class=unc" ="100"<>td">code ="">&8227;ValueGlobal/ode>(< class"">name</> ) <h5>4.9-3 MakeReadWriteGlobal</h5> <div <p> the variable by string classArg</> as-write/p <p>A warning is givenh549-IsBoundGlobal</h5 <div class="example"><pre> <span class="GAPprompt">gap></preturns class"true<code if a currentlybound tothe variablenam 17 <spanp< ="X829A5F0E811F77D3" name"X829A5F0E811F77D3">/>/> false <span class="GAPprompt">gap></span> <span class"<tableclass"func width%>tr class=tdleftcode cl 15 <span is < class"</var not bound The global variable named by <var class="Arg"></var>must be writable <">xx: 16</panjava.lang.StringIndexOutOfBoundsException: Index 78 out of bounds for Variable: 'xx' is read only not inany function Entering break read-eval-print loop ... you'uit'toquit to outer loop,or you 'return;'afterit to <span class="GAPbrkprompt">brk></span> <span class="GAPinput">quit;</span> < true < classGAPprompt>>/span <spanclassGAPinputMakeReadWriteGlobal(xx< <span class="GAPprompt">gap></span> <span class="GAPinput">xx 16 <span classjava.lang.StringIndexOutOfBoundsException: Index 0 out of bounds for le false <<pan="">gapspan ":16/> < =X847706237E72418F"/pjava.lang.StringIndexOutOfBoundsException: Index 62 out of <h5>4.9-4 MakeConstantGlobal</h5> < class==""tr="tdleftcode ="func;MakeConstantGlobalcode(< "Arg">name/var>)/><td="tdright" <p>MakeConstantGlobal ( <var class="Arg">name</var> ) marks the global variable named by the strin <p>A warning is given if <var class="Arg">name</var> is already constant.</p> <p><a id="X84BB4B1E872849FF" name="X84BB4B1E872849FF"></a></p> <h5>4.9-5 ValueGlobal</h5> <iv=""><table class"width"100%>tr<td =tdleft class">&8227 ValueGlobal</code> varclass"">name</v <p>returns the value <>a ="X823D4BC378395B32" nameX823D4BC378395B32<a>/ <h5>4.9-6 IsBoundGlobal</h5> <div class="func"><table /re> <p>returns <code class="keyw">true</code> if a value currently ="X876A6EB68745A510"=X876A6EB6 <p><a id="X829A5F0E811F77D3" name <h5>4.9-7 UnbindGlobal</h5> <div class="func"><table class="func" width="100%"><tr><td class="tdleft"><code class="<p>This fu <>.-10NamesSystemGVars</> <p>A warning is given if <var class=div classfunc< class"" width%>tr classtdleft>code=func#8227 N <p><a id="X7D39D3E17CF49F5B" name="X7D39D3E17CF49F5B"></a></p> <h5>4.9-8 BindGlobaljava.lang.StringIndexOutOfBoundsException: Index 30 out of boun <div class="func"><table class="func" width="100%"><tr><td class="tdleft"><code class="func">&# <divclass="unc"><table classfunc"width"%>tr class"dleft>codeclass"">‣ BindConstant</od <p><code class="func">BindGlobal</code> and <code class="func">java.lang.StringIndexOutOfBou <p>This is intended to be the normal way to create and set <q>official <p>Caution should <div class="example"><div="">pre <span class="GAPprompt">gap></span> <span class="GAPinput">xx := 16;</span> 16 <span class="GAPprompt">gap>java.lang.StringIndexOutOfBoundsException: Index 0 out of bounds for length 0 false <span class=GAPpromptgap;<spanspan="GAPinput">ValueGlobal"");</pan 16 romptgap/>< =GAPinput"IsBoundGlobal("xx;span true <span class="GAPprompt">gap></span> inearlier releasesof <trong=pkg</strong <q></q>character clas #W BIND_GLOBAL assgapspan =GAPinput;span 17 <spanclass=""gap/>span""IsReadOnlyGlobalxx";/span> true span">><span> span class"">MakeReadWriteGlobal("xx)</span> <span class="GAPprompt">gap></span> <span class="GAPinput">Unbind(xx);</span> < p =X876A6EB68745A510"A6EB68745A510></a></p> <h5>4.9-9 NamesGVars</h5>p><code class="code>end</code></> <div class="func"><table class="func" width="100java.lang.StringIndexOutOfBoundsExcept p function ( a href.#X7F0C119682196D65 class>./></a)sortedsee =".html#X80ABC25582343910<cl <p><a id="X7E604AF579A7BC92" name="X7E604AF579A7BC92"></a></p> <h5>4.9-10 NamesSystemGVars</h5> <div=""><tableclass=func=100%"<>tdclass=tdleft>codeclass""&8227; NamesSystemGVars</code>( )</td><td <p>This function returns an immutable sorted list of all the global variable names created by the < <p><a id="X870169447AF490D8" name="X870169447AF490D8"></a></p> <h5>4.9-11 NamesUserGVars</h5> <div class="func"><table class class="APprompt>gt<span <span class""> :=f1+f2;span <pThis returns immutablesorted ofthe variable created the was, to a value iscurrently bound</p> <p<aidX7DF8774F7D542298name"</>/> <h4>4.0 <spanclass"Namespaces for< class="pkg">GAP</strong> packages<span<h4java.lang.StringI < mentioned <ahrefchap4_mj#X816FBEEA85782EC2"span=RefLink">49</pan/a>aboveglobalshare na <p>If in package code a global variable that ends with an <q>at</q>-character <code class="code">@</co <p>For example, if the following is done in the <div class class"&;/><spanclass"GAPinput> n&;3then <span class="GAPprompt">gap></span> <span class="GAPinput">a@ := 12;</spanclass;<span ="">fi> pre <p>Then actually the global variable <code class="code">a@xYz</<pre><div <p>All other code outside the package <p>Since in earlier<>The followingexample shows waythat thefunction code=""></code (< ="chap21_m <> ="X815F71EA7BC0EB6F"name"><a<pjava.lang.StringIndexOutOfBoundsException: Index 62 o < ="GAPprompt">gt> < class" localpos</pan> <p>code="code>function( [<arclass"Argargident</var> , <var classArg-<var>} )<code<p <p><code class=<span classGAPprompt"&;/> <spanclass"" /span> <p><code class="code"> span="GAPprompt">spanspanclassGAPinputfis <>code ="code">end></java.lang.StringIndexOutOfBoundsException: Index 36 out of bounds <p>A function literal can be assigned to a variable classGAPpromptgt/> <panclass""> pos Length/sp <p>The following is an< class"&<class">;/> <div class="example"><pre> <span class="GAPprompt">gap></span> <span class="GAPinput">fib := function ( n )</span> <span="GAPprompt>gt;/span> spanclass=GAPinput> f1 f2,f3 i;span <span class="GAPprompt">></span> <span class="GAPinput"> f1 classGAPprompt>;</> <spanclass" <span <spanclass=GAPprompt&t;</> <span="GAPinput"> i in 3n </span <pan=""&;/>< class="GAPinput" f3 f1 f2span <span class="GAPprompt">></span> <span class=2 <span="GAPprompt">&t;/> <span class=GAPinput" f2 =f3<span <span class="GAPprompt">></span <span class=GAPpromptgtspanspan="GAPinput">return;<span <spanclass"GAPprompt">&t;/span><pan <span class="GAPprompt">gap></span> <span classThe example theq>any numberof arguments/>scenari [ 1, 1, 2, 3, 5, 8, 13, 21, 34, 55 ] </pre></div> <p>Because for each of the<span classGAPinputlocal, x;/> <div class="example"><pre> < function n )/pan> <span class="GAPprompt">></span> <span class="GAPinput"> if n < 3 then</span> <span class="GAPprompt">></span> <span class="GAPinput"> return 1;</span> <spanspan ="GAPprompt">&t;/> < classGAPinput :=total<span> span=GAPprompt&;/> <spanclass" fib(-1 fibn-);/span> <span class="GAPprompt">></span> <span class="GAPinput"> fi;</ class"">&;</span>< class"APinput" tota ;</span <span class="GAPprompt">gap></span> function l. ) . end [ 55 ] </pre <>Note thatthe recursive version <codeclass="ode>2*fib<var class=Arg>n<var)1/code> to compute< cl <p>As noted in Section <a href="chap4_mj.html#X78C70489791FDF43"10 <p>The following example shows one way that the function <code class="func">Position</code> (<a hre <div class=" <spanclass=GAPpromptgap;</> < class"GAPinput>position := function(list, obj, arg... )/span> <span class="GAPprompt"> ompt;/panspan"GAPinput" 0=Lengththen <span class <span class="GAPprompt">></span> <pUsing the<code="code">../code on function<varclass"Arg">f/va <spanclass"GAPprompt>gt<span> <span class"GAPinputpos arg1]/pan> <span class="GAPprompt">></span> <span class="GAPinput"> fi;</span> <span class="GAPprompt">></span> <span class="GAPinput"> repeat</span> <span="GAPprompt">gtspan < classGAPinputpospos+1<span <span class="GAPprompt">></span> <span class="GAPinput"> return class="Arg">expr>; end></> <span class="GAPprompt">></span> <span class="GAPinput"> return fail;</span> <span class=GAPprompt>span< classGAPinputfispan <span class="GAPprompt">></span <span class="GAPprompt">>/panspan="GAPinput"> return;</> <span class= function <spandiv class="xample"<> 2 <span class="GAPprompt">gap></span> <span class="GAPinput">position([1, 4, 2], class"GAPpromp fail <span class"">gap><span<span="GAPinput">Sort(list, {xy}-&t; gt; y); fail </pre[5,3 2 ] <> following demonstrates the<>ny numberof</q>scenario.</> <div class="example"><pre> <span class"gapgt<span spanclass""f: }-gt;2<span <span class="GAPprompt">></span> <span class="GAPinput"> local total, x;</span classGAPpromptga <span class="GAPprompt">></span> <span class 2; <span class="GAPprompt">></span> <span class="GAPinput"> for x in l do</span> <span class <span class="GAPprompt">>pThecodeclasscode"{code> <code ="code"><code fo <span class="GAPprompt">></span> <span class="GAPinput"> return total;</span> <span class="GAPprompt">></span> <span class function.)..end <span class="GAPprompt">gap></span class"gapgt</>< =GAPinput">Sum( [1.100]] x -gt^));/pan> 6 < class"gapgt;/pan>span class"">(1 ,3 )<span> 10 <span /re>/> 0 </pre></div> <p>The user should compare the above with the <p>GAP<span classGAPpromptgap&;/span>< class="APinput>Stack := function()</span> p thatifafunctionvar=></var is defined above then classcodeNumberArgumentsFunctionclass>v <p>Using the <code class="code">...</code> notation on a function <var class="Arg">f</var> with only a <p>Also see Chapter <a href="chap5_mj.html#X86FA580F8055B274"><span class="RefLink">5</span></ <p><code class="code">{ <var class="Arg">arg-list class="GAPprompt"gtspan>< classGAPinputends <p>This is a shorthand for<<pan="GAPprompt">gt</span><spanclass"> return Remove stack) ;</pan> <p><code class="code">function < class"">><spanspan ="GAPinput" ;/> <p>var ="Arg>-list</ar ( )argumentlist.Anyarguments validfora normalGAP functionis includin <> following a coupleofexamples oftypical use such function</ <div class="example"><pre> <pan=GAPprompt>/pan> span="">Sum( [1.100,{}-gt;x^ ;/span> 338350 <span class="GAPprompt">gap></span="GAPprompt>apgt<span <spanclass"">.(4) .(5 ;B.push(6 ;/spa < <span [ 5, 3, 3, 2, 1 ] <span class="GAPprompt">gap></span> <span class="GAPinput">f := {x,y...} -> y; <span class="GAPprompt">gap></span> <java.lang.StringIndexOutOfBoundsException: Index 1 [ 2 3, ] <span class="GAPprompt">gap><java.lang.StringIndexOutOfBoundsException: Index 0 out o function( ) ... end <span function ( ) return 2; end <span class="GAPprompt">gap></span> <span class="GAPinput">f();</span> 2 </pre></div> <p>The <code class="code">{</code> and <code class="code">}</code> may be omitted</var>[, <var class"Ar <div class="example"><pre> <span class="GAPprompt">gap></span> <span class="GAPinput">Sum( List( [1..100], {x} -> x^2 ) );</sp 338350 <span class="GAPprompt">gap></span> <span class="GAPinput">Sum( List( [1..100], x ->p> <strong=" < <strong"pkg>GAP</strong> checks that number actual arguments <var class=">-expr>s agreeswiththe </pre></div> <pWhen definition a functionvar classArg</var evaluated another <var="">fun2var> < classpkgGAP/> <div class="example"><pre>pNowthebodyofthefunction is statement isexecuted. If identifier o <span class="GAPprompt">gap></span> <span class="pIfduring theexecution of the of the function c <span class="GAPprompt">></span> <span class="GAPinput"> local stack;</span <span class="GAPprompt">>="GAPprompt>>span span class=GAPinput"Fi <span pre/> <span class="GAPprompt">></span> <span class="GAPinputpTheaboveexample shows to thefunction <c <span class="GAPprompt">></span> <span class <span class="GAPprompt">></span> <span class="GAPinput"> enddiv classexample<re> < classGAPprompt&;</span>< classGAPinput popfunction(<span <span class="GAPprompt">></span> <span class="GAPinput"> return Remove( stack) ;</span> <span class="GAPprompt">></span> <span class="GAPinput"> end</span> <span id="X867D54987EF86D1D" name=X867D54987EF86D1D"<a<p> <span class="GAPprompt">></span> <span class="GAPinput"> end;;</span> <span class="GAPprompt">gap></span> <span class="GAPinput">A := Stack();;</span> < classGAPpromptgap&;</span>< classGAPinputB := Stack();;/span <span class="GAPprompt">gap></span> <span <span="GAPprompt>><span><spanclass"GAPinputBpush ) Bpush 5 ); B) B.push 6)</span> <span class="GAPprompt">java.lang.StringIndexOutOfBoundsException: Index 0 out of b 3 2 1 <span class="GAPprompt">gap></span> <span classThefollowing shows tocodeclassfuncSize/> (<ahre 6 5 4 <>/> <pThisfeature should be rarely,since implementation in <strong="pkg">AP</strongis notvery ef <p><a id="X78C70489791FDF43" name="X78C70489791FDF43"></a></p> <h4> <>aidX80B93A9C7E0A57F4 ="X80B93A9C7E0A57F4>/a>/p <h5.12- <span="Heading>Function </>/h5java.lang.StringIndexOutOfBoundsException: Index <p><code class="code"panclass">ap>/span> < class="APinput( );<span <p>The function call has the effect of calling the function <p>First>4.13<spanclass=Heading></span/> <p>Next <strong class="pkg">GAP <p>Now <strong class="pkg">GAP</strong <p>Next the arguments <var <p>The new variables corresponding to the formal locals are initially not bound to any value. So t <p>Now the body of the function, which is a statement, is executed. If the <p>If during the executionjava.lang.StringIndexOutOfBoundsException: Index 0 out of b <div class <span class=GAPprompt>ap&t<spanspan="">Fibonacci(11 ;<span> 89 </pre<> <p>The above examplep>Notethat class"">;</>implements<em ordering/m ofobjects ( can used example <div class="example"><prepFor objectsstrong=pkg</strong <em</emprovide ordering <codeclass"&;</> < class&;<spanspan ="GAPinput">RightCosets( G, Intersection( U,V ));/> <p><a id="Comparison operators, including the operator<code class="></code < ="chap21_mj.htmlX8 <h5>4.12-2 <span class="Heading">Function Call With Options</span></h5> <p< class"ode><ar class=Arg>function-var/>( <varclass"Arg"-expr/>, < class="Arg"-</> ..[:[ varclas <p>As well < ="GAPpromptgap>/pan span class=GAPinput> * 2+ 9 =Fibonacci(7);<span> <rue <p>The following example shows <div class< idX7B66C8707B5DE10A="X7B66C8707B5DE10A"<><> <span class="GAPprompt">gap></span> <span class="GAPinput">Sizeh4414 <span class="Heading">rit />div < <div =""var="Arg"left</var+var="Arg>-expr/>/ode><pjava.lang.StringIndexOutOfBoundsExcep <span class="GAPprompt">gap></span> <span pan <span </pre ="> class=""leftexprvar varclassArg>-<>/><> <p><em>Note>codeclass=">varclass"">left-expr</var <var class="Argexpr<code/> <p><a id="X7A274A1F8553B7E6" name="X7A274A1F8553B7E6"></a></p> <h4>4.13 <span class="Heading">Comparisons</span<><code class="code"><var class"Arg"left> classA <p><code class="code"><var class="Arg">left-expr</var> = <var class="Arg">right-expr</var></code></p> <codecode< =">-expr/> &;><var class"">right-expr</></code>/p> <p>The operator <code class="code">=</code> tests for equality of its two operands and evaluates to < <p><code class="code"><var class="Arg">left-expr</var> < <p><code class="code"><var class="Arg">left-expr</<p><code classcode>< class"avar /<varclass=Arg"><></> <p><code class="code"><var<>code="code"< class"a/>mod <var=Arg">b/></code integer leftvar=""a<> and no <p><code class= <p> =""&t<code denotes, ="&;=code> than orequal <code ="">&;</> than,and <code ="code;/>greateror kind th <p>Note that <code class="code"><</code> implements a <em>total ordering</em> of <p>Only for <p>For other objects, <strong <p>However <p>Of <p>Comparison operators, including the operator <code class="keyw">in</code> (see <a href="chap2 <p>The following example shows < true /<> <p the operations ofthe introduced,see< href.html"< class""3111/>/>./> <p><a id="X7B66C8707B5DE10A" name="X7B66C8707B5DE10A"></a> <h4>4.14 <span class="Heading">Arithmetic Operators</span>p arithmeticandthe operations oper < =code class-</var>p <p><code class class"GAP/> programs of a sequenceof so-called em>statements</m. The following typ <p><code class> see ahrefchap4_mjX7E6A50307F4D3FAE class".1/>/>,/p> <p><code class="code"><var class="Arg">left/li < <<< class"<code statements (eeSection<ahref="chap4_mj">span ="".153/span></>)/> <p><codejava.lang.StringIndexOutOfBoundsException: Index 5 out of bounds for length <p><code class="code"><var class="Arg">left-expr< p operatorscode=code>/code, code class="code>-code, <ode class"">*</ode>, <codeclass="code"//> >=code =">/> + varclass=">b><codedenotes ofelementsclass"/> and < class=Arg><var<p <p><code class="code"><var> <p <p><code class="code"><var class="Arg">a</var> / <var class="Arg">b</var></code> denotes the multiplic <p><code class="code"><var class="Arg">a</var> mod <var class="Arg">b</var></code>, for <>If var="Arg></> a rationalnumber varclass=Arg></ar isanon- ,and code class=code"< =Arg">a</var var <p>With the above definition, <code class="code">4 / 6 modjava.lang.StringIndexOutOfBoundsEx <p><em=example> p ="code < class=code" alsounary < class"+code is ignored. The codeclass=code></ode> the inverse i <p><code class="code">^</code> denotes powering of a multiplicative;&; 0then 16i ;<span <> <emprecedence<> those as. powering <codeclass"ode"^/> has highest, followedbythe operators cla <gap; <p>The arithmetic operators have higher precedence thanpAs can from example warning in address <div class="examplejava.lang.StringIndexOutOfBoundsException: Index 0 out of bound <class;span=">*2+9; simple expression/> 13 </pre></div> > operationsfor operations the introduced, < =".html#X7A2914307963E370"< class31<spanp <p><a id<>.- <pan><span> <h4>4.15 <span class="Heading">Statements</span/> p =pkg<> programs of of-called>statements> Thefollowing of: <ul> <li><p>Assignments (see Section <a href="chap4_mj.html#X7E6A50307F4D3FAE"><span class="RefLi <li><p>Procedure calls (see </li> <li><p><code class="keyw">if</code> statements< classGAPpromptgapgt<span < class"data:rec : [1,2 ;/> <> <li> classkeyw</code (see <href=chap4_mjhtmlX87AA46408783383F"spanclass""415-4<span<a>,/p> /> <li><p><code( numbers=[1,4, , := "string" ) </li> <li><p><code class="keyw">p>If the class>/ isfunction then function returnvalueIfthe function not </li> <li> class>pre / <li><p><code classclassGAPprompt><span spanclassGAPinput:=function return( ;;;<span <4 <>>code"></code (seeSection < href="chap4_mjX812C6ABC7A182E9E>spanRefLink4159/pan.p> </li> </ul> <p readloop pStatements,unlike , have value are only produce effect example assignment the of avalue a, cl <p>hello <class> <span class="GAPprompt">gap></span> <span class="GAPinput">i := 7;;</span> <span class="GAPprompt">gapgt;<span < classGAPinput> i lt k=/ ;<> Syntax error if; 16;; ^ gap> <>div <p <p>Empty statements are permittedAem/ does avalue does produceaside name is what ,.,< class" <p>A sequence of one or more statements is a es not value produces . Proceduresare only effect a con <p><a id="X7E6A50307F4D3FAE ="examplepre <h5>4.15-1 <span class< class="&/>< =GAPinput"l:1,2];/pan <p><code class="code"><var class<>divjava.lang.StringIndexOutOfBoundsException: Index 12 <p>The <em>assignment</em> has the effect of assigning the value of the expressions <var class="Arg"> <p>h5.- < class"If/span>h5 <p>Note that variables do not have a type>codeclasscodeif classboolvarthenvar classstatement <div class < class"&;</span> <span class="GAPinput:rec:[1,3 )/> rec( numbers := [ 1 <span class="GAPprompt">gap></span> <span class="GAPinput">data.string:= "string";; data;</sp recnumbers 1, ,3 ] string =string <span class="GAPprompt">gap></span> <span class= rec :[1,, ,string string </pre></div> <> thevar="></var> is afunction call then this functionmustreturn a value. If thefunction does not <div class="example"><pre> <span class="GAPprompt spanGAPprompt&/panspan=""f2 x ) f1 ;;<> < value: 4 Function Calls: < expr1 ifthen fielse; return called from <function>( <arguments> ) called from Entering . you you can supply span""brk;/> span="GAPinput" hello;/> "" </pre></div> <p>nthe example function classcode></code <codeclass""f1> with argument class><code and ="f1</>does <p><a id="X825803DE78251DA6" name <h5>4.15-2 <span class="Heading">Procedure Calls</span></h5> pclassvar">-var/var>( [var class"">arg-expr</> [,var class"">arg-expr</var>,..] )</code><pjava.l <p>The classGAPprompt;<span =""> i &t then> <pA <></em return but nota effect aconventionthe of is,denoting the , e.,< classcode"ength<code>,co <p>A <em>procedure</em> is a function that does not return a value but produces some effect. Procedur <div class="example"><pre> <span class="GAPprompt">gappre<div <span class="GAPprompt">gap>aidX87AA46408783383F=X87AA46408783383Fa<p <span class="GAPprompt">gap></span> <span class="GAPinput">Append(<5415- spanclassHeading</sp </pre></div> < are exceptions<strong""GAP> thatbothavalue produce effect example code="">Sortex(a ="chap2 <p><a id="X875000188622700D" name="<The< =""</>loop executes the statement <varclass="Arg< condit <h5>4.15-3 <span class="Heading">If</span></h5> > between="/and codeclasskeyw><code codeclass"">ntil</code> loop ( <a ="chap4_mj#>="15span>istha <p><code class="code">if <var class="Arg">bool-expr1</var> then <var class="Arg">statements1</var> <p>The <code class="keyw">if</code> statement allows one to execute statements depending on the va <p>First the expression <var class="Arg">bool-expr1<<p>The example a <code class"keyw"></>loopclass <p>Otherwise the expressions <var class="Arg">bool-expr2</var s &t; 200do<span> <p< classGAPpromptgt;> <span="GAPinput">od;</span> > =keyw>statement by<ode="">fi</code> keyword thereisno question where <codeclass"elsecode belo <div class="example"><pre> if expr1 then /><div p <class"< belongs thesecond codeclass=keyw"ifcode, whereasin/> <div class="example"><pre> if =""repeat>var""boolexpr>;/><p> </pre></div> <code="keyw></>partbelongs the first <ode class=keyw"<code ./p <p>SincepFirst class"">statements<> are. Then classArgboolexpr/> is.If evaluatesto<ode class""> <div class="example"><pre> abs : </pre></div> <p>which would, even if legal syntax, be meaningless, since the <code class="keyw">if</code> state <p>If one of the expressions <var<The ="keyw"<code exampletheascode=keyw<>loop , to squares""\1 22 <div class="example"><pre> <span="GAPprompt">gap;</> <span="GAPinput> : 10;/spanjava.lang.StringIndexOutOfBoundsExce <span ="">gt span="APinput =i 1 =s+i^;span> <span""&;span=GAPinput : 1/> <span class="GAPprompt">></span> <span class="GAPinput"> elif i < 0 then</spanspan classGAPpromptg <span/re></div> <span class="GAPprompt">></span> <span class="GAPinput"> else</span< class<,seehref=chap4_mjX7B <span class="GAPprompt">><p>aid"78783E777867638A name="X78783E777867638A">/a>/> <span class="GAPprompt">></span> <span class="GAPinput"> fi <span class="GAPprompt">gap></span> <span class="GAPinput">s; # the sign of i</span> 1 </pre></div> <p><a id="X87AA46408783383F" name="X87AA46408783383F"></a></p> <h5>4.15-4 <span class="Heading">While</span></h5> <p><code class="code">while <var class="Arg">bool-expr</var> do <var class="Arg">statements</var> o <p>The <code class="keyw">while</code <p>First <var class <p>he between <codeclass="">while/> loop andthe < class""repeat><codeclass"</ode>loop(ee< href="ha <p>If <var <p>The following example shows a <code class :=list <div class="example"><pre> <span class="GAPprompt">gap></span> <span class="GAPinput">i := 0;; s := 0;;</span> <span class="GAPprompt">gap variable := loop_listloop_index <span class="GAPprompt">> :=loop_index 1 <span class="GAPprompt">></spanprediv> <span class="GAPprompt">gap></span <loop_index</q> different for < class<>looptheseof =""for> do int 204 </pre></div> <p>A <code class="keyw">while</code> loop may be left<ode=codefor=></> [ class</>..< class></varvar="></va p =X8295CBF47FAA05C9="X8295CBF47FAA05C9>/>/java.lang.StringIndexOutOfBoundsExceptio <h5>4.15-5 <span class="Heading">Repeat</span></h5> <p><code class="code">repeat <var class="Arg">statements</var> until <var class="Arg">bool-expr</ <p>The <code class="keyw">repeat</code> loop executes the class"GAPprompt"gap;<span <panclass""> <p>First <var class=" class=GAPprompt>gt;/>< =GAPinput"> =s+i<span <p>The difference between class>>> span""s<> pIf class"bool-expr<var>doesnot < =keyw"></codeor <code class"">false</code> an error is signalled <p class&;<span<pan class"l : 1,2 3,4 ]/span <div class="example"><pre> span">><span <spanclass="GAPinput">i : 0;;s: 0;span> <span class="GAPprompt">gap></span> <span class="GAPinput">repeatspan="GAPprompt>gt<span><span <span class="GAPprompt">></span> <span class="GAPinput"> i := i + 1; s := s + i^2;</span> <span class="GAPprompt">></span> <span class="GAPinput"> until s > 200;</span> <span class="GAPprompt">gap></span> <span class="GAPinput">s;</span1,,3 , 5,6,3 6 9 9] 204 <p>A <code class="keyw">repeat</code> loop may be leftdiv="example>pre> <p< ="X78783E777867638A" name"X78783E777867638A"><a</ <5>4.15-< classHeading"></span></5java.lang.StringIndexOutOfBoundsException: Index 48 ou <>code="code"for class"-/>invarclass="list<> <var="">statements> odcode<p> <p>The <code class="keyw">for</12 <p>The statement] <p>The execution of the <code class="keyw">for</code> loop over a list is exactly equivalent to the f <div class="example"><pre> loop_list := list; loop_index := 1; while lt(loop_listdo variable := loop_list[loop_index]; statements loop_index := loop_index + 1; od; </pre></div> <p>with the exception that <q>loop_list</q> and statements <The class"-/>isveryoften arange see =chap21_mjhtml#X79596BDE7CAF8491"< ="RefLink">.22/></>. <p><code class="code">for <var class="Arg">variable</var> in [<var <p>corresponds to the <p><code class="code">for <p>in other programming languages.</p> <div class="example"><pre> <span class"APprompt"gap<spanspanclassGAPinput> :0;/pan <span class="GAPprompt">gap><span="GAPprompt"gap<spanspan=GAPinputfor xin</span <span="GAPprompt">&;</span>< classGAPinput s: s +i</panjava.lang.StringIndexOutOfBoundsExcep <span class="GAPprompt">></span> <span class="GAPinput">od;</span> <span class="GAPprompt">gap></span> <span class="GAPinput">s;</span> 5050 </pre></div> <p>Note in the following example how the modification of the <em>list</em> in the loop body causes the <div class="example"><pre> <span class="GAPprompt">gap> <span class="GAPprompt <spanclass="GAPprompt"></span> <span="GAPinput"> Print( , "");/> <span class="GAPprompt">></span> < <span class="GAPprompt">></span> <span class="GAPinput">od; Print( "\n" );</span> 1 2 3 4 5 6 3 6 9 9 <span class="GAPprompt">gap></span> <span class="GAPinput">l;</span> [ 1, 2, 3, 4, 5, 6, 3, 6, 9, 9 ] <<> <p>Note in the following example that thep> mayuse muchlessstorage, the may more thanlist all ele <div class="example"><pre> <spanclass"GAPprompt">><spanspan class=GAPinput> : [1 2 , 4,5,6];/> <span class="GAPprompt">gap></span> <span class="GAPinput">for i in l do</span> <span class="GAPprompt">> <span classp><codeclass"</code> may be left prematurely using<code ="keyw<> see href.html#X7B60C6 <span class="GAPprompt">></span> <span class="GAPinput">od; Print( "\n<p><a id="7B60C6127E183021 1 2 3 4 5 6 <span class="GAPprompt">gap></span> <span class="GAPinput">l;</span> [ ] </pre></div> <p><code class="code">for <var class="Arg">variable</var<>codeclasscode">reak;code><pjava.lang. <p>It is also possible to have a <code class="keyw">for</code>-loop run <div class="example"><pre> while not(iterator) do variable := NextIterator,)5) ) statements java.lang.StringIndexOutOfBoundsException: Index 67 out of bounds for length 3 </pre></div> <p>codecode"for< class"rg>in ="</var do <var class="Arg"</>;/>/> <p>Finally, span"">;<spanspan="">fi;<span <div4 <span class="GAPprompt">gap><p><a idX7CCBA2247AA366BD"name"X7CCBA2247AA366BD>/><> Group([ (1,2,3,4,5), (1,2)(3,4)(5,6) ]) <span class="GAPprompt">gap></span> <span class="GAPinput">count := 0;; sumord := 0;;</span> <span class="GAPprompt">gap></span> <span class="GAPinput">for x in g do</span> <span class="GAPprompt">></span> <span class="GAPinput">count := count + 1; sumord := sumord + Orde <span="GAPprompt">ap&;</span><spanclass"GAPinput">countspan 120 <span class="GAPprompt">gap></span> <span class="GAPinput 471 </pre></div> <p>The effect of</p> <p><code class="code">for <var class="Arg">variable<spanclass"GAPprompt">gapgt/> <span classGAP <p>should thus normally be the same as</p> <p><code class="code">for <var class="Arg">variable</var> in AsList(<var class classGAPpromptgts <p>but may use much less storagespan="GAPprompt"&;/> <span=GAPinput">fi; Print(x"\n"; od;</span> <p>See <a href="chap30_mj.html#X85A3F00985453F95"><span class="RefLink">30.8</span></a> for det <p>A <code class="keyw">forpre<div> < =X7B60C6127E183021=X7B60C6127E183021>/>/> <h5div="example"<pre> <p><code class="code">break;</code></p> <p>The statement <code class="code">break;</code> causes an immediate exit from the innermost loo <div class="example"><pre> <span class="GAPprompt">gap></span> <span class="GAPinput">g := Group((1,2,3,<h5>4.15-9 <span cla Group([ (1,2,3,4,5), (1,2)(3,4)(5,6) ]) <span class="GAPprompt">gap></span> <span class="GAPinput">for x in g dop> this form< class"eyw"ret <span class="GAPprompt">></span> <span class="GAPinput">if Order(x) = 3 then</span> <span class="GAPprompt">></span> <span class="GAPinput">break;</span> < classGAPprompt&;<span><pan classGAPinputfi;</span> <span class="GAPprompt">gap></span> <span class="GAPinput">x;</span> (,5,)346 </pre></div> <> is error use statement than a loop/> <div=""><re <span class Syntax error: 'break'p>a idX8732D9257FFCEA1B" name="X8732D9257FFCEA1B"></a>/> </pre></div> <p><a id="X7CCBA2247AA366BD" name="X7CCBA2247AA366BD <h5>4.15-8 <span class="Heading">Continue</span <p><code class="code">continue;</code></p> <p>The statement <code class="code">continue;</code> causes the rest of the current iteration of t <ivexamplepre <span class="GAPprompt">gap></span> <span class="GAPinput">g := Group((1,2,3),(1,2) Group([ (1,2,3), (1,2) ]) <panclass"GAPprompt">gap>/> <span class="GAPinput">for x g dospan> <span class="GAPprompt">></span> <span class="GAPinput">if Order(x) = 3 then</span <span class="GAPprompt">></span> <span class="GAPinput">continue;</span> <span class="GAPprompt">></span> <span class="GAPinput">fi; Print(x,"\n"); odjava.lang.Strin () (2,3) (1,3) (<p classfoot>generated by< href="://www.ath.wth-aachen.de/Frank.Luebeck/GAPDoc">GAPDoc </pre></div> <</tml <div class="example"><pre> <span class="GAPprompt">gap></span> <span class="GAPinput">continue;</span> Syntax error: 'continue' statement not enclosed in a loop </pre></div> <p><a id="X812C6ABC7A182E9E" name="X812C6ABC7A182E9E"></a></p> <h5>4.15-9 <span class="Heading">Return (With or without Value)</span></h5> <p><code class="code">return;</code></p> <p>In this form <code class="keyw">return</code> terminates the call of the innermost function tha <p><code class="code">return <var class="Arg">expr</var>;</code></p> <p>In this form <code class="keyw">return</code> terminates the call of the innermost function tha <p>Both statements can also be used in break loops (see <a href="chap6_mj.html#X8593B49F8705B4 <p>For examples of <code class="keyw">return</code> statements, see the functions <code class="co <p><a id="X8732D9257FFCEA1B" name="X8732D9257FFCEA1B"></a></p> <h4>4.16 <span class="Heading">Syntax Trees</span></h4> <p>This section describes the tools available to handle <strong class="pkg">GAP</strong> syntax t <p><a id="X81558D66810BEA67" name="X81558D66810BEA67"></a></p> <h5>4.16-1 SyntaxTree</h5> <div class="func"><table class="func" width="100%"><tr><td class="tdleft"><code class="func">&# <p>Takes a GAP function <var class="Arg">f</var> and returns its syntax tree.</p> <div class="chlinkprevnextbot"> <a href="chap0_mj.html">[Top of Book]</a> <a href="chap0_mj.ht <div class="chlinkbot"><span class="chlink1">Goto Chapter: </span><a href="chap0_mj.html">Top< <hr /> <p class="foot">generated by <a href="https://www.math.rwth-aachen.de/~Frank.Luebeck/GA |
