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<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"/><title>4&nbsp;Racket Interoperability</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"/><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="../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,&quot;tocview_0&quot;);">&#9660;</a></td><td></td><td><a href="index.html" class="tocviewlink" data-pltdoc="x">Datalog:<span class="mywbr"> &nbsp;</span> Deductive Database Programming</a></td></tr></table></div><div class="tocviewsublistonly" style="display: block;" id="tocview_0"><table cellspacing="0" cellpadding="0"><tr><td align="right">1&nbsp;</td><td><a href="datalog.html" class="tocviewlink" data-pltdoc="x">Datalog Module Language</a></td></tr><tr><td align="right">2&nbsp;</td><td><a href="Tutorial.html" class="tocviewlink" data-pltdoc="x">Tutorial</a></td></tr><tr><td align="right">3&nbsp;</td><td><a href="Parenthetical_Datalog_Module_Language.html" class="tocviewlink" data-pltdoc="x">Parenthetical Datalog Module Language</a></td></tr><tr><td align="right">4&nbsp;</td><td><a href="" class="tocviewselflink" data-pltdoc="x">Racket Interoperability</a></td></tr><tr><td align="right">5&nbsp;</td><td><a href="Acknowledgments.html" class="tocviewlink" data-pltdoc="x">Acknowledgments</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._datalog%2Fmain..rkt%29._theory%2Fc%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">theory/<span class="mywbr"> &nbsp;</span>c</span></span></a></td></tr><tr><td><a href="#%28def._%28%28lib._datalog%2Fmain..rkt%29._make-theory%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">make-<wbr></wbr>theory</span></span></a></td></tr><tr><td><a href="#%28def._%28%28lib._datalog%2Fmain..rkt%29._write-theory%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">write-<wbr></wbr>theory</span></span></a></td></tr><tr><td><a href="#%28def._%28%28lib._datalog%2Fmain..rkt%29._read-theory%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktValLink">read-<wbr></wbr>theory</span></span></a></td></tr><tr><td><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktStxLink">datalog</span></span></a></td></tr><tr><td><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%21%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktStxLink">datalog!</span></span></a></td></tr><tr><td><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._%21%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktStxLink">!</span></span></a></td></tr><tr><td><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~7e%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktStxLink">~</span></span></a></td></tr><tr><td><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3a-%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktStxLink">:<span class="mywbr"> &nbsp;</span>-</span></span></a></td></tr><tr><td><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3f%29%29" class="tocsublink" data-pltdoc="x"><span class="RktSym"><span class="RktStxLink">?</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" style="color: #888;" type="text" value="...search manuals..." title="Enter a search string to search the manuals" onkeypress="return DoSearchKey(event, this, &quot;6.7&quot;, &quot;../&quot;);" onfocus="this.style.color=&quot;black&quot;; this.style.textAlign=&quot;left&quot;; if (this.value == &quot;...search manuals...&quot;) this.value=&quot;&quot;;" onblur="if (this.value.match(/^ *$/)) { this.style.color=&quot;#888&quot;; this.style.textAlign=&quot;center&quot;; this.value=&quot;...search manuals...&quot;; }"/></form>&nbsp;&nbsp;<a href="../index.html" title="up to the documentation top" data-pltdoc="x" onclick="return GotoPLTRoot(&quot;6.7&quot;);">top</a></span><span class="navright">&nbsp;&nbsp;<a href="Parenthetical_Datalog_Module_Language.html" title="backward to &quot;3 Parenthetical Datalog Module Language&quot;" data-pltdoc="x">&larr; prev</a>&nbsp;&nbsp;<a href="index.html" title="up to &quot;Datalog: Deductive Database Programming&quot;" data-pltdoc="x">up</a>&nbsp;&nbsp;<a href="Acknowledgments.html" title="forward to &quot;5 Acknowledgments&quot;" data-pltdoc="x">next &rarr;</a></span>&nbsp;</div><h3 x-source-module="(lib &quot;datalog/scribblings/datalog.scrbl&quot;)" x-source-pkg="datalog" x-part-tag="&quot;interop&quot;">4<tt>&nbsp;</tt><a name="(part._interop)"></a><a name="(mod-path._datalog)"></a>Racket Interoperability</h3><p><table cellspacing="0" cellpadding="0" class="defmodule"><tr><td align="left"><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=require.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._require%2529%2529&amp;version=6.7" class="RktStxLink Sq" data-pltdoc="x">require</a></span><span class="stt"> </span><a href="" class="RktModLink" data-pltdoc="x"><span class="RktSym">datalog</span></a><span class="RktPn">)</span></td><td align="right"><span class="RpackageSpec"><span class="Smaller">&nbsp;package:</span> <span class="stt">datalog</span></span></td></tr></table></p><p>The Datalog database can be directly used by Racket programs through this API.</p><p><div class="SIntrapara">Examples:</div><div class="SIntrapara"><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=define.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._define%2529%2529&amp;version=6.7" class="RktStxLink Sq" data-pltdoc="x">define</a></span><span class="hspace">&nbsp;</span><span class="RktSym">family</span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28lib._datalog%2Fmain..rkt%29._make-theory%29%29" class="RktValLink" data-pltdoc="x">make-theory</a></span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%29%29" class="RktStxLink" data-pltdoc="x">datalog</a></span><span class="hspace">&nbsp;</span><span class="RktSym">family</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._%21%29%29" class="RktStxLink" data-pltdoc="x">!</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">parent</span><span class="hspace">&nbsp;</span><span class="RktSym">joseph2</span><span class="hspace">&nbsp;</span><span class="RktSym">joseph1</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._%21%29%29" class="RktStxLink" data-pltdoc="x">!</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">parent</span><span class="hspace">&nbsp;</span><span class="RktSym">joseph2</span><span class="hspace">&nbsp;</span><span class="RktSym">lucy</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._%21%29%29" class="RktStxLink" data-pltdoc="x">!</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">parent</span><span class="hspace">&nbsp;</span><span class="RktSym">joseph3</span><span class="hspace">&nbsp;</span><span class="RktSym">joseph2</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'()</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%29%29" class="RktStxLink" data-pltdoc="x">datalog</a></span><span class="hspace">&nbsp;</span><span class="RktSym">family</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3f%29%29" class="RktStxLink" data-pltdoc="x">?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">parent</span><span class="hspace">&nbsp;</span><span class="RktSym">X</span><span class="hspace">&nbsp;</span><span class="RktSym">joseph2</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'(#hasheq((X . joseph3)))</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%29%29" class="RktStxLink" data-pltdoc="x">datalog</a></span><span class="hspace">&nbsp;</span><span class="RktSym">family</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3f%29%29" class="RktStxLink" data-pltdoc="x">?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">parent</span><span class="hspace">&nbsp;</span><span class="RktSym">X</span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=symbols.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._string-%7E3esymbol%2529%2529&amp;version=6.7" class="RktValLink Sq" data-pltdoc="x">string-&gt;symbol</a></span><span class="hspace">&nbsp;</span><span class="RktVal">"joseph2"</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'(#hasheq((X . joseph3)))</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=let.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fletstx-scheme..rkt%2529._let%2529%2529&amp;version=6.7" class="RktStxLink Sq" data-pltdoc="x">let</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym">atom</span><span class="hspace">&nbsp;</span><span class="RktVal">'</span><span class="RktVal">joseph2</span><span class="RktPn">]</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%29%29" class="RktStxLink" data-pltdoc="x">datalog</a></span><span class="hspace">&nbsp;</span><span class="RktSym">family</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3f%29%29" class="RktStxLink" data-pltdoc="x">?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">parent</span><span class="hspace">&nbsp;</span><span class="RktSym">X</span><span class="hspace">&nbsp;</span><span class="RktRdr">#,</span><span class="RktSym">atom</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'(#hasheq((X . joseph3)))</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=let.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fletstx-scheme..rkt%2529._let%2529%2529&amp;version=6.7" class="RktStxLink Sq" data-pltdoc="x">let</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym">table</span><span class="hspace">&nbsp;</span><span class="RktVal">'</span><span class="RktVal">parent</span><span class="RktPn">]</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%29%29" class="RktStxLink" data-pltdoc="x">datalog</a></span><span class="hspace">&nbsp;</span><span class="RktSym">family</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3f%29%29" class="RktStxLink" data-pltdoc="x">?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktRdr">#,</span><span class="RktSym">table</span><span class="hspace">&nbsp;</span><span class="RktSym">X</span><span class="hspace">&nbsp;</span><span class="RktSym">joseph2</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'(#hasheq((X . joseph3)))</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%29%29" class="RktStxLink" data-pltdoc="x">datalog</a></span><span class="hspace">&nbsp;</span><span class="RktSym">family</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3f%29%29" class="RktStxLink" data-pltdoc="x">?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">parent</span><span class="hspace">&nbsp;</span><span class="RktSym">joseph2</span><span class="hspace">&nbsp;</span><span class="RktSym">X</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'(#hasheq((X . joseph1)) #hasheq((X . lucy)))</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%29%29" class="RktStxLink" data-pltdoc="x">datalog</a></span><span class="hspace">&nbsp;</span><span class="RktSym">family</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3f%29%29" class="RktStxLink" data-pltdoc="x">?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">parent</span><span class="hspace">&nbsp;</span><span class="RktSym">joseph2</span><span class="hspace">&nbsp;</span><span class="RktSym">X</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3f%29%29" class="RktStxLink" data-pltdoc="x">?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">parent</span><span class="hspace">&nbsp;</span><span class="RktSym">X</span><span class="hspace">&nbsp;</span><span class="RktSym">joseph2</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'(#hasheq((X . joseph3)))</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%29%29" class="RktStxLink" data-pltdoc="x">datalog</a></span><span class="hspace">&nbsp;</span><span class="RktSym">family</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._%21%29%29" class="RktStxLink" data-pltdoc="x">!</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3a-%29%29" class="RktStxLink" data-pltdoc="x">:-</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">ancestor</span><span class="hspace">&nbsp;</span><span class="RktSym">A</span><span class="hspace">&nbsp;</span><span class="RktSym">B</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym">parent</span><span class="hspace">&nbsp;</span><span class="RktSym">A</span><span class="hspace">&nbsp;</span><span class="RktSym">B</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._%21%29%29" class="RktStxLink" data-pltdoc="x">!</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3a-%29%29" class="RktStxLink" data-pltdoc="x">:-</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">ancestor</span><span class="hspace">&nbsp;</span><span class="RktSym">A</span><span class="hspace">&nbsp;</span><span class="RktSym">B</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym">parent</span><span class="hspace">&nbsp;</span><span class="RktSym">A</span><span class="hspace">&nbsp;</span><span class="RktSym">C</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=generic-numbers.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._%7E3d%2529%2529&amp;version=6.7" class="RktValLink Sq" data-pltdoc="x">=</a></span><span class="hspace">&nbsp;</span><span class="RktSym">D</span><span class="hspace">&nbsp;</span><span class="RktSym">C</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym">ancestor</span><span class="hspace">&nbsp;</span><span class="RktSym">D</span><span class="hspace">&nbsp;</span><span class="RktSym">B</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'()</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%29%29" class="RktStxLink" data-pltdoc="x">datalog</a></span><span class="hspace">&nbsp;</span><span class="RktSym">family</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3f%29%29" class="RktStxLink" data-pltdoc="x">?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">ancestor</span><span class="hspace">&nbsp;</span><span class="RktSym">A</span><span class="hspace">&nbsp;</span><span class="RktSym">B</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"><tr><td><p><span class="RktRes">'(#hasheq((A . joseph3) (B . joseph2))</span></p></td></tr><tr><td><p><span class="RktRes"></span><span class="hspace">&nbsp;&nbsp;</span><span class="RktRes">#hasheq((A . joseph2) (B . lucy))</span></p></td></tr><tr><td><p><span class="RktRes"></span><span class="hspace">&nbsp;&nbsp;</span><span class="RktRes">#hasheq((A . joseph2) (B . joseph1))</span></p></td></tr><tr><td><p><span class="RktRes"></span><span class="hspace">&nbsp;&nbsp;</span><span class="RktRes">#hasheq((A . joseph3) (B . lucy))</span></p></td></tr><tr><td><p><span class="RktRes"></span><span class="hspace">&nbsp;&nbsp;</span><span class="RktRes">#hasheq((A . joseph3) (B . joseph1)))</span></p></td></tr></table></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=let.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fletstx-scheme..rkt%2529._let%2529%2529&amp;version=6.7" class="RktStxLink Sq" data-pltdoc="x">let</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktPn">[</span><span class="RktSym">x</span><span class="hspace">&nbsp;</span><span class="RktVal">'</span><span class="RktVal">joseph2</span><span class="RktPn">]</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%29%29" class="RktStxLink" data-pltdoc="x">datalog</a></span><span class="hspace">&nbsp;</span><span class="RktSym">family</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3f%29%29" class="RktStxLink" data-pltdoc="x">?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">parent</span><span class="hspace">&nbsp;</span><span class="RktSym">x</span><span class="hspace">&nbsp;</span><span class="RktSym">X</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'(#hasheq((X . joseph1)) #hasheq((X . lucy)))</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%29%29" class="RktStxLink" data-pltdoc="x">datalog</a></span><span class="hspace">&nbsp;</span><span class="RktSym">family</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3f%29%29" class="RktStxLink" data-pltdoc="x">?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=generic-numbers.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._add1%2529%2529&amp;version=6.7" class="RktValLink Sq" data-pltdoc="x">add1</a></span><span class="hspace">&nbsp;</span><span class="RktVal">1</span><span class="hspace">&nbsp;</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3a-%29%29" class="RktStxLink" data-pltdoc="x">:-</a></span><span class="hspace">&nbsp;</span><span class="RktSym">X</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'(#hasheq((X . 2)))</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%29%29" class="RktStxLink" data-pltdoc="x">datalog</a></span><span class="hspace">&nbsp;</span><span class="RktSym">family</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3f%29%29" class="RktStxLink" data-pltdoc="x">?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=generic-numbers.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._add1%2529%2529&amp;version=6.7" class="RktValLink Sq" data-pltdoc="x">add1</a></span><span class="hspace">&nbsp;</span><span class="RktSym">X</span><span class="hspace">&nbsp;</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3a-%29%29" class="RktStxLink" data-pltdoc="x">:-</a></span><span class="hspace">&nbsp;</span><span class="RktVal">2</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'()</span></p></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="stt">&gt; </span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%29%29" class="RktStxLink" data-pltdoc="x">datalog</a></span><span class="hspace">&nbsp;</span><span class="RktSym">family</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3f%29%29" class="RktStxLink" data-pltdoc="x">?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktRdr">#,</span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=lambda.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fbase..rkt%2529._%7Ece%7Ebb%2529%2529&amp;version=6.7" class="RktStxLink Sq" data-pltdoc="x">&#955;</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">x</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=generic-numbers.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._%252B%2529%2529&amp;version=6.7" class="RktValLink Sq" data-pltdoc="x">+</a></span><span class="hspace">&nbsp;</span><span class="RktSym">x</span><span class="hspace">&nbsp;</span><span class="RktVal">1</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span><span class="RktVal">1</span><span class="hspace">&nbsp;</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3a-%29%29" class="RktStxLink" data-pltdoc="x">:-</a></span><span class="hspace">&nbsp;</span><span class="RktSym">X</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></td></tr><tr><td><p><span class="RktRes">'(#hasheq((X . 2)))</span></p></td></tr></table></blockquote></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>value</p></div></div><p class="RForeground"><a name="(def._((lib._datalog/main..rkt)._theory/c))"></a><span title="Provided from: datalog | Package: datalog"><span class="RktSym"><a href="#%28def._%28%28lib._datalog%2Fmain..rkt%29._theory%2Fc%29%29" class="RktValDef RktValLink" data-pltdoc="x">theory/c</a></span></span><span class="hspace">&nbsp;</span>:<span class="hspace">&nbsp;</span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=contract-utilities.html%23%2528def._%2528%2528lib._racket%252Fcontract%252Fprivate%252Fguts..rkt%2529._contract%7E3f%2529%2529&amp;version=6.7" class="RktValLink Sq" data-pltdoc="x">contract?</a></span></p></blockquote></td></tr></table></blockquote></div><div class="SIntrapara"> A contract for Datalog theories. </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._((lib._datalog/main..rkt)._make-theory))"></a><span title="Provided from: datalog | Package: datalog"><span class="RktSym"><a href="#%28def._%28%28lib._datalog%2Fmain..rkt%29._make-theory%29%29" class="RktValDef RktValLink" data-pltdoc="x">make-theory</a></span></span><span class="RktPn"></span><span class="RktPn">)</span><span class="hspace">&nbsp;</span>&rarr;<span class="hspace">&nbsp;</span><span class="RktSym"><a href="#%28def._%28%28lib._datalog%2Fmain..rkt%29._theory%2Fc%29%29" class="RktValLink" data-pltdoc="x">theory/c</a></span></p></blockquote></td></tr></table></blockquote></div><div class="SIntrapara"> Creates a theory for use with <span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%29%29" class="RktStxLink" data-pltdoc="x">datalog</a></span>. </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._((lib._datalog/main..rkt)._write-theory))"></a><span title="Provided from: datalog | Package: datalog"><span class="RktSym"><a href="#%28def._%28%28lib._datalog%2Fmain..rkt%29._write-theory%29%29" class="RktValDef RktValLink" data-pltdoc="x">write-theory</a></span></span><span class="hspace">&nbsp;</span><span class="RktVar">t</span><span class="RktPn">)</span><span class="hspace">&nbsp;</span>&rarr;<span class="hspace">&nbsp;</span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=void.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._void%2529%2529&amp;version=6.7" class="RktValLink Sq" data-pltdoc="x">void</a></span></p></blockquote></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;</span><span class="RktVar">t</span><span class="hspace">&nbsp;</span>:<span class="hspace">&nbsp;</span><span class="RktSym"><a href="#%28def._%28%28lib._datalog%2Fmain..rkt%29._theory%2Fc%29%29" class="RktValLink" data-pltdoc="x">theory/c</a></span></td></tr></table></blockquote></div><div class="SIntrapara"> Writes a theory to the current output port. Source location information is lost. 
</div><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._datalog/main..rkt)._read-theory))"></a><span title="Provided from: datalog | Package: datalog"><span class="RktSym"><a href="#%28def._%28%28lib._datalog%2Fmain..rkt%29._read-theory%29%29" class="RktValDef RktValLink" data-pltdoc="x">read-theory</a></span></span><span class="RktPn"></span><span class="RktPn">)</span><span class="hspace">&nbsp;</span>&rarr;<span class="hspace">&nbsp;</span><span class="RktSym"><a href="#%28def._%28%28lib._datalog%2Fmain..rkt%29._theory%2Fc%29%29" class="RktValLink" data-pltdoc="x">theory/c</a></span></p></blockquote></td></tr></table></blockquote></div><div class="SIntrapara"> Reads a theory from the current input port. </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>syntax</p></div></div><table cellspacing="0" cellpadding="0" class="RktBlk RForeground"><tr><td><span class="RktPn">(</span><a name="(form._((lib._datalog/main..rkt)._datalog))"></a><span title="Provided from: datalog | Package: datalog"><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%29%29" class="RktStxDef RktStxLink" data-pltdoc="x">datalog</a></span></span><span class="hspace">&nbsp;</span><span class="RktVar">thy-expr</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktVar">stmt</span><span class="hspace">&nbsp;</span><span class="RktMeta">...</span><span class="RktPn">)</span></td></tr></table></blockquote></td></tr><tr><td><span class="stt">&nbsp;</span></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="argcontract"><tr><td><span class="hspace">&nbsp;&nbsp;</span></td><td><span class="RktVar">thy-expr</span></td><td><span class="hspace">&nbsp;</span></td><td>:</td><td><span class="hspace">&nbsp;</span></td><td><span class="RktSym"><a href="#%28def._%28%28lib._datalog%2Fmain..rkt%29._theory%2Fc%29%29" class="RktValLink" data-pltdoc="x">theory/c</a></span></td></tr></table></td></tr></table></blockquote></div><div class="SIntrapara"> Executes the statements on the theory given by <span class="RktVar">thy-expr</span>. Returns the answers to the final query as a list of substitution dictionaries or returns <span class="RktSym">empty</span>. </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>syntax</p></div></div><table cellspacing="0" cellpadding="0" class="RktBlk RForeground"><tr><td><span class="RktPn">(</span><a name="(form._((lib._datalog/main..rkt)._datalog!))"></a><span title="Provided from: datalog | Package: datalog"><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%21%29%29" class="RktStxDef RktStxLink" data-pltdoc="x">datalog!</a></span></span><span class="hspace">&nbsp;</span><span class="RktVar">thy-expr</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktVar">stmt</span><span class="hspace">&nbsp;</span><span class="RktMeta">...</span><span class="RktPn">)</span></td></tr></table></blockquote></td></tr><tr><td><span class="stt">&nbsp;</span></td></tr><tr><td><table cellspacing="0" cellpadding="0" class="argcontract"><tr><td><span class="hspace">&nbsp;&nbsp;</span></td><td><span class="RktVar">thy-expr</span></td><td><span class="hspace">&nbsp;</span></td><td>:</td><td><span class="hspace">&nbsp;</span></td><td><span class="RktSym"><a href="#%28def._%28%28lib._datalog%2Fmain..rkt%29._theory%2Fc%29%29" class="RktValLink" data-pltdoc="x">theory/c</a></span></td></tr></table></td></tr></table></blockquote></div><div class="SIntrapara"> Executes the statements on the theory given by <span class="RktVar">thy-expr</span>. Prints the answers to every query in the list of statements. Returns <span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=void.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._void%2529%2529&amp;version=6.7" class="RktValLink Sq" data-pltdoc="x">void</a></span><span class="RktPn">)</span>. </div></p><p>Statements are either assertions, retractions, or queries.</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>syntax</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(form._((lib._datalog/main..rkt)._!))"></a><span title="Provided from: datalog | Package: datalog"><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._%21%29%29" class="RktStxDef RktStxLink" data-pltdoc="x">!</a></span></span><span class="hspace">&nbsp;</span><span class="RktVar">clause</span><span class="RktPn">)</span></p></blockquote></td></tr></table></blockquote></div><div class="SIntrapara"> Asserts the clause. 
</div><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>syntax</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(form._((lib._datalog/main..rkt)._~7e))"></a><span title="Provided from: datalog | Package: datalog"><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~7e%29%29" class="RktStxDef RktStxLink" data-pltdoc="x">~</a></span></span><span class="hspace">&nbsp;</span><span class="RktVar">clause</span><span class="RktPn">)</span></p></blockquote></td></tr></table></blockquote></div><div class="SIntrapara"> Retracts the literal. </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>syntax</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(form._((lib._datalog/main..rkt)._~3a-))"></a><span title="Provided from: datalog | Package: datalog"><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3a-%29%29" class="RktStxDef RktStxLink" data-pltdoc="x">:-</a></span></span><span class="hspace">&nbsp;</span><span class="RktVar">literal</span><span class="hspace">&nbsp;</span><span class="RktVar">question</span><span class="hspace">&nbsp;</span><span class="RktMeta">...</span><span class="RktPn">)</span></p></blockquote></td></tr></table></blockquote></div><div class="SIntrapara"> A conditional clause. </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>syntax</p></div></div><p class="RForeground"><span class="RktPn">(</span><a name="(form._((lib._datalog/main..rkt)._~3f))"></a><span title="Provided from: datalog | Package: datalog"><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3f%29%29" class="RktStxDef RktStxLink" data-pltdoc="x">?</a></span></span><span class="hspace">&nbsp;</span><span class="RktVar">question</span><span class="RktPn">)</span></p></blockquote></td></tr></table></blockquote></div><div class="SIntrapara"> Queries the literal and prints the result literals. </div></p><p>Questions are either literals or external queries.</p><p>Literals are represented as <span class="RktSym">identifier</span> or <span class="RktPn">(</span><span class="RktSym">table</span><span class="stt"> </span><span class="RktSym">term</span><span class="stt"> </span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=stx-patterns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fstxcase-scheme..rkt%2529._......%2529%2529&amp;version=6.7" class="RktStxLink Sq" data-pltdoc="x">...</a></span><span class="RktPn">)</span>.</p><p>A table is either an identifier or <span class="RktRdr">#,</span><span class="RktSym">expr</span> where <span class="RktSym">expr</span>
evaluates to a symbol.</p><p>External queries are represented as <span class="RktPn">(</span><span class="RktSym">ext-table</span><span class="stt"> </span><span class="RktSym">term</span><span class="stt"> </span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=stx-patterns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fstxcase-scheme..rkt%2529._......%2529%2529&amp;version=6.7" class="RktStxLink Sq" data-pltdoc="x">...</a></span><span class="stt"> </span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3a-%29%29" class="RktStxLink" data-pltdoc="x">:-</a></span><span class="stt"> </span><span class="RktSym">term</span><span class="stt"> </span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=stx-patterns.html%23%2528form._%2528%2528lib._racket%252Fprivate%252Fstxcase-scheme..rkt%2529._......%2529%2529&amp;version=6.7" class="RktStxLink Sq" data-pltdoc="x">...</a></span><span class="RktPn">)</span>, where <span class="RktSym">ext-table</span> is an identifier bound to a
procedure or <span class="RktRdr">#,</span><span class="RktSym">expr</span> where <span class="RktSym">expr</span> evaluates to a
procedure that when given the first set of terms as arguments returns
the second set of terms as values.</p><p>A term is either a non-capitalized identifiers for a constant symbol,
a Racket expression for a constant datum, or a capitalized identifier
for a variable symbol, or <span class="RktRdr">#,</span><span class="RktSym">expr</span> where <span class="RktSym">expr</span>
evaluates to a constant datum. Bound identifiers in terms are treated
as the datum they are bound to.</p><p>External queries fail if any logic variable is not fully resolved to a
datum on the Datalog side. In other words, unbound logic variables
never flow to Racket.</p><p>External queries invalidate Datalog&rsquo;s guaranteed termination. For
example, this program does not terminate:</p><blockquote class="SCodeFlow"><table cellspacing="0" cellpadding="0" class="RktBlk"><tr><td><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._datalog%29%29" class="RktStxLink" data-pltdoc="x">datalog</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28def._%28%28lib._datalog%2Fmain..rkt%29._make-theory%29%29" class="RktValLink" data-pltdoc="x">make-theory</a></span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._%21%29%29" class="RktStxLink" data-pltdoc="x">!</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3a-%29%29" class="RktStxLink" data-pltdoc="x">:-</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">loop</span><span class="hspace">&nbsp;</span><span class="RktSym">X</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="https://download.racket-lang.org/docs/6.7/html/local-redirect/index.html?doc=reference&amp;rel=generic-numbers.html%23%2528def._%2528%2528quote._%7E23%7E25kernel%2529._add1%2529%2529&amp;version=6.7" class="RktValLink Sq" data-pltdoc="x">add1</a></span><span class="hspace">&nbsp;</span><span class="RktSym">X</span><span class="hspace">&nbsp;</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3a-%29%29" class="RktStxLink" data-pltdoc="x">:-</a></span><span class="hspace">&nbsp;</span><span class="RktSym">Z</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym">loop</span><span class="hspace">&nbsp;</span><span class="RktSym">Z</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr><tr><td><span class="hspace">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="RktPn">(</span><span class="RktSym"><a href="#%28form._%28%28lib._datalog%2Fmain..rkt%29._~3f%29%29" class="RktStxLink" data-pltdoc="x">?</a></span><span class="hspace">&nbsp;</span><span class="RktPn">(</span><span class="RktSym">loop</span><span class="hspace">&nbsp;</span><span class="RktVal">1</span><span class="RktPn">)</span><span class="RktPn">)</span><span class="RktPn">)</span></td></tr></table></blockquote><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, &quot;6.7&quot;, &quot;../&quot;);" onfocus="this.style.color=&quot;black&quot;; this.style.textAlign=&quot;left&quot;; if (this.value == &quot;...search manuals...&quot;) this.value=&quot;&quot;;" onblur="if (this.value.match(/^ *$/)) { this.style.color=&quot;#888&quot;; this.style.textAlign=&quot;center&quot;; this.value=&quot;...search manuals...&quot;; }"/></form>&nbsp;&nbsp;<a href="../index.html" title="up to the documentation top" data-pltdoc="x" onclick="return GotoPLTRoot(&quot;6.7&quot;);">top</a></span><span class="navright">&nbsp;&nbsp;<a href="Parenthetical_Datalog_Module_Language.html" title="backward to &quot;3 Parenthetical Datalog Module Language&quot;" data-pltdoc="x">&larr; prev</a>&nbsp;&nbsp;<a href="index.html" title="up to &quot;Datalog: Deductive Database Programming&quot;" data-pltdoc="x">up</a>&nbsp;&nbsp;<a href="Acknowledgments.html" title="forward to &quot;5 Acknowledgments&quot;" data-pltdoc="x">next &rarr;</a></span>&nbsp;</div></div></div><div id="contextindicator">&nbsp;</div></body></html>