<HTML> <HEAD> <!-- Created by texi2html 1.56k + clip patches and <A href="http://www.clip.dia.fi.upm.es/Software">lpdoc</A> from ciao.texi on 28 January 2007 --> <LINK rel="stylesheet" href="ciao.css" type="text/css"> <TITLE>The Ciao Prolog System - Comparing terms</TITLE> </HEAD> <BODY> Go to the <A HREF="ciao_1.html">first</A>, <A HREF="ciao_20.html">previous</A>, <A HREF="ciao_22.html">next</A>, <A HREF="ciao_241.html">last</A> section, <A HREF="ciao_toc.html">table of contents</A>. <P><HR><P> <H1><A NAME="SEC144" HREF="ciao_toc.html#TOC144">Comparing terms</A></H1> <P> <A NAME="IDX1462"></A> <P> <STRONG>Author(s):</STRONG> Daniel Cabeza, Manuel Hermenegildo. <P> <STRONG>Version:</STRONG> 1.10#7 (2006/4/26, 19:22:13 CEST) <P> <STRONG>Version of last change:</STRONG> 1.9#199 (2003/12/19, 18:18:33 CET) <P> These built-in predicates are extra-logical. They treat uninstantiated variables as objects with values which may be compared, and they never instantiate those variables. They should <EM>not</EM> be used when what you really want is arithmetic comparison or unification. <P> The predicates make reference to a <A NAME="IDX1463"></A> <A NAME="IDX1464"></A> <EM>standard total ordering</EM> of terms, which is as follows: <UL> <LI>Variables, by age (roughly, oldest first -- the order is <EM>not</EM> related to the names of variables). <LI>Floats, in numeric order (e.g. -1.0 is put before 1.0). <LI>Integers, in numeric order (e.g. -1 is put before 1). <LI>Atoms, in alphabetical (i.e. character code) order. <LI>Compound terms, ordered first by arity, then by the name of the principal functor, then by the arguments in left-to-right order. Recall that lists are equivalent to compound terms with principal functor <CODE>'.'/2</CODE>. </UL> <P> For example, here is a list of terms in standard order: <PRE> [ X, -1.0, -9, 1, bar, foo, [1], X = Y, foo(0,2), bar(1,1,1) ] </PRE> <UL> <LI><A HREF="ciao_21.html#SEC145">Usage and interface (term_compare)</A> <LI><A HREF="ciao_21.html#SEC146">Documentation on exports (term_compare)</A> </UL> <H2><A NAME="SEC145" HREF="ciao_toc.html#TOC145">Usage and interface (<CODE>term_compare</CODE>)</A></H2> <div class="cartouche"> <UL> <LI><STRONG>Library usage:</STRONG> These predicates are builtin in Ciao, so nothing special has to be done to use them. <LI><STRONG>Exports:</STRONG> <UL> <LI><EM>Predicates:</EM> <A NAME="IDX1465"></A> <CODE>compare/3</CODE>. <LI><EM>Properties:</EM> <A NAME="IDX1466"></A> <CODE>==/2</CODE>, <A NAME="IDX1467"></A> <CODE>\==/2</CODE>, <A NAME="IDX1468"></A> <CODE>@</2</CODE>, <A NAME="IDX1469"></A> <CODE>@=</2</CODE>, <A NAME="IDX1470"></A> <CODE>@>/2</CODE>, <A NAME="IDX1471"></A> <CODE>@>=/2</CODE>. </UL> </UL> </div class="cartouche"> <H2><A NAME="SEC146" HREF="ciao_toc.html#TOC146">Documentation on exports (<CODE>term_compare</CODE>)</A></H2> <P> <A NAME="IDX1472"></A> <A NAME="IDX1473"></A> <DL> <DT><span class="define">PROPERTY:</span> <B>==/2:</B> <DD><A NAME="IDX1474"></A> <P> <STRONG>Usage:</STRONG> <CODE>Term1 == Term2</CODE> <UL> <LI><EM>Description:</EM> The terms <CODE>Term1</CODE> and <CODE>Term2</CODE> are strictly identical. <LI><EM>The following properties should hold globally:</EM> <CODE>Term1</CODE> is not further instantiated. (<CODE>basic_props:not_further_inst/2</CODE>) <CODE>Term2</CODE> is not further instantiated. (<CODE>basic_props:not_further_inst/2</CODE>) This predicate is understood natively by CiaoPP. (<CODE>basic_props:native/1</CODE>) </UL> </DL> <P> <A NAME="IDX1475"></A> <A NAME="IDX1476"></A> <DL> <DT><span class="define">PROPERTY:</span> <B>\==/2:</B> <DD><A NAME="IDX1477"></A> <P> <STRONG>Usage:</STRONG> <CODE>Term1 \== Term2</CODE> <UL> <LI><EM>Description:</EM> The terms <CODE>Term1</CODE> and <CODE>Term2</CODE> are not strictly identical. <LI><EM>The following properties should hold globally:</EM> <CODE>Term1</CODE> is not further instantiated. (<CODE>basic_props:not_further_inst/2</CODE>) <CODE>Term2</CODE> is not further instantiated. (<CODE>basic_props:not_further_inst/2</CODE>) This predicate is understood natively by CiaoPP. (<CODE>basic_props:native/1</CODE>) </UL> </DL> <P> <A NAME="IDX1478"></A> <A NAME="IDX1479"></A> <DL> <DT><span class="define">PROPERTY:</span> <B>@</2:</B> <DD><A NAME="IDX1480"></A> <P> <STRONG>Usage:</STRONG> <CODE>@<(Term1, Term2)</CODE> <UL> <LI><EM>Description:</EM> The term <CODE>Term1</CODE> precedes the term <CODE>Term2</CODE> in the standard order. <LI><EM>The following properties should hold globally:</EM> <CODE>Term1</CODE> is not further instantiated. (<CODE>basic_props:not_further_inst/2</CODE>) <CODE>Term2</CODE> is not further instantiated. (<CODE>basic_props:not_further_inst/2</CODE>) This predicate is understood natively by CiaoPP. (<CODE>basic_props:native/1</CODE>) </UL> </DL> <P> <A NAME="IDX1481"></A> <A NAME="IDX1482"></A> <DL> <DT><span class="define">PROPERTY:</span> <B>@=</2:</B> <DD><A NAME="IDX1483"></A> <P> <STRONG>Usage:</STRONG> <CODE>@=<(Term1, Term2)</CODE> <UL> <LI><EM>Description:</EM> The term <CODE>Term1</CODE> precedes or is identical to the term <CODE>Term2</CODE> in the standard order. <LI><EM>The following properties should hold globally:</EM> <CODE>Term1</CODE> is not further instantiated. (<CODE>basic_props:not_further_inst/2</CODE>) <CODE>Term2</CODE> is not further instantiated. (<CODE>basic_props:not_further_inst/2</CODE>) This predicate is understood natively by CiaoPP. (<CODE>basic_props:native/1</CODE>) </UL> </DL> <P> <A NAME="IDX1484"></A> <A NAME="IDX1485"></A> <DL> <DT><span class="define">PROPERTY:</span> <B>@>/2:</B> <DD><A NAME="IDX1486"></A> <P> <STRONG>Usage:</STRONG> <CODE>@>(Term1, Term2)</CODE> <UL> <LI><EM>Description:</EM> The term <CODE>Term1</CODE> follows the term <CODE>Term2</CODE> in the standard order. <LI><EM>The following properties should hold globally:</EM> <CODE>Term1</CODE> is not further instantiated. (<CODE>basic_props:not_further_inst/2</CODE>) <CODE>Term2</CODE> is not further instantiated. (<CODE>basic_props:not_further_inst/2</CODE>) This predicate is understood natively by CiaoPP. (<CODE>basic_props:native/1</CODE>) </UL> </DL> <P> <A NAME="IDX1487"></A> <A NAME="IDX1488"></A> <DL> <DT><span class="define">PROPERTY:</span> <B>@>=/2:</B> <DD><A NAME="IDX1489"></A> <P> <STRONG>Usage:</STRONG> <CODE>@>=(Term1, Term2)</CODE> <UL> <LI><EM>Description:</EM> The term <CODE>Term1</CODE> follows or is identical to the term <CODE>Term2</CODE> in the standard order. <LI><EM>The following properties should hold globally:</EM> <CODE>Term1</CODE> is not further instantiated. (<CODE>basic_props:not_further_inst/2</CODE>) <CODE>Term2</CODE> is not further instantiated. (<CODE>basic_props:not_further_inst/2</CODE>) This predicate is understood natively by CiaoPP. (<CODE>basic_props:native/1</CODE>) </UL> </DL> <P> <A NAME="IDX1490"></A> <A NAME="IDX1491"></A> <DL> <DT><span class="define">PREDICATE:</span> <B>compare/3:</B> <DD><A NAME="IDX1492"></A> <P> <CODE>compare(Op, Term1, Term2)</CODE> <P> <CODE>Op</CODE> is the result of comparing the terms <CODE>Term1</CODE> and <CODE>Term2</CODE>. <P> <STRONG>Usage:</STRONG> <CODE>compare(?atm, @term, @term)</CODE> <UL> <LI><EM>The following properties hold upon exit:</EM> <CODE>?atm</CODE> is an element of <CODE>[=,>,<]</CODE>. (<CODE>basic_props:member/2</CODE>) <CODE>@term</CODE> is any term. (<CODE>basic_props:term/1</CODE>) <CODE>@term</CODE> is any term. (<CODE>basic_props:term/1</CODE>) <LI><EM>The following properties hold globally:</EM> This predicate is understood natively by CiaoPP. (<CODE>basic_props:native/1</CODE>) </UL> </DL> <P><HR><P> Go to the <A HREF="ciao_1.html">first</A>, <A HREF="ciao_20.html">previous</A>, <A HREF="ciao_22.html">next</A>, <A HREF="ciao_241.html">last</A> section, <A HREF="ciao_toc.html">table of contents</A>. </BODY> </HTML>
