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<H1><A NAME="SEC210" HREF="ciao_toc.html#TOC210">Defining operators</A></H1>
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<STRONG>Author(s):</STRONG> Adapted from SICStus 0.6 code; modifications and documentation by Daniel Cabeza and Manuel Carro.
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<STRONG>Version:</STRONG> 1.10#7 (2006/4/26, 19:22:13 CEST)
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<STRONG>Version of last change:</STRONG> 1.9#287 (2004/2/13, 18:59:4 CET)
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Operators allow writting terms in a more clear way than the standard functional notation. Standard operators in Ciao are defined by this predicate (but note that the compiler itself defines more operators at compile time):
<PRE>
standard_ops :-
op(1200,xfx,[:-]),
op(1200,fx,[:-,?-]),
op(1100,xfy,[;]),
op(1050,xfy,[->]),
op(1000,xfy,[',']),
op(900,fy,[\+]),
op(700,xfx,[=,\=,==,\==,@<,@>,@=<,@>=,=..,is,=:=,=\=,<,=<,>,>=]),
op(550,xfx,[:]),
op(500,yfx,[+,-,/\,\/,#]),
op(500,fy,[++,--]),
op(400,yfx,[*,/,//,rem,mod,<<,>>]),
op(200,fy,[+,-,\]),
op(200,xfx,[**]),
op(200,xfy,[^]).
</PRE>
<UL>
<LI><A HREF="ciao_40.html#SEC211">Usage and interface (operators)</A>
<LI><A HREF="ciao_40.html#SEC212">Documentation on exports (operators)</A>
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<H2><A NAME="SEC211" HREF="ciao_toc.html#TOC211">Usage and interface (<CODE>operators</CODE>)</A></H2>
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<UL>
<LI><STRONG>Library usage:</STRONG>
<CODE>:- use_module(library(operators)).</CODE>
<LI><STRONG>Exports:</STRONG>
<UL>
<LI><EM>Predicates:</EM>
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<CODE>op/3</CODE>,
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<CODE>current_op/3</CODE>,
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<CODE>current_prefixop/3</CODE>,
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<CODE>current_infixop/4</CODE>,
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<CODE>current_postfixop/3</CODE>.
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<H2><A NAME="SEC212" HREF="ciao_toc.html#TOC212">Documentation on exports (<CODE>operators</CODE>)</A></H2>
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<DL>
<DT><span class="define">PREDICATE:</span> <B>op/3:</B>
<DD><A NAME="IDX2934"></A>
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<CODE>op(Precedence, Type, Name)</CODE>
<P>
Declares the atom <CODE>Name</CODE> to be an operator of the stated <CODE>Type</CODE> and <CODE>Precedence</CODE> (0 =< <CODE>Precedence</CODE> =< 1200). <CODE>Name</CODE> may also be a list of atoms in which case all of them are declared to be operators. If <CODE>Precedence</CODE> is 0 then the operator properties of <CODE>Name</CODE> (if any) are cancelled. Note that, unlike in
<A NAME="IDX2935"></A>
ISO-Prolog, it is allowed to define two operators with the same name, one infix and the other postfix.
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<STRONG>Usage:</STRONG> <CODE>op(+int, +operator_specifier, +atm_or_atm_list)</CODE>
<KBD> * ISO * </KBD>
<UL>
<LI><EM>The following properties hold globally:</EM>
This predicate is understood natively by CiaoPP.
(<CODE>basic_props:native/1</CODE>)
</UL>
</DL>
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<A NAME="IDX2937"></A>
<DL>
<DT><span class="define">PREDICATE:</span> <B>current_op/3:</B>
<DD><A NAME="IDX2938"></A>
<P>
<CODE>current_op(Precedence, Type, Op)</CODE>
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The atom <CODE>Op</CODE> is currently an operator of type <CODE>Type</CODE> and precedence <CODE>Precedence</CODE>. Neither <CODE>Op</CODE> nor the other arguments need be instantiated at the time of the call; i.e., this predicate can be used to generate as well as to test.
<P>
<STRONG>Usage:</STRONG> <CODE>current_op(?int, ?operator_specifier, ?atm)</CODE>
<KBD> * ISO * </KBD>
<UL>
<LI><EM>The following properties hold globally:</EM>
This predicate is understood natively by CiaoPP.
(<CODE>basic_props:native/1</CODE>)
</UL>
</DL>
<P>
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<DL>
<DT><span class="define">PREDICATE:</span> <B>current_prefixop/3:</B>
<DD><A NAME="IDX2941"></A>
<P>
<CODE>current_prefixop(Op, Less, Precedence)</CODE>
<P>
Similar to
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<CODE>current_op/3</CODE>, but it concerns only the prefix operators. It returns <STRONG>only one solution</STRONG>. Not a predicate for general use.
</DL>
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<A NAME="IDX2944"></A>
<DL>
<DT><span class="define">PREDICATE:</span> <B>current_infixop/4:</B>
<DD><A NAME="IDX2945"></A>
<P>
<CODE>current_infixop(Op, LeftLess, Prec, RightLess)</CODE>
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Similar to
<A NAME="IDX2946"></A>
<CODE>current_op/3</CODE>, but it concerns only infix operators. It returns <STRONG>only one solution</STRONG>. Not a predicate for general use.
</DL>
<P>
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<DL>
<DT><span class="define">PREDICATE:</span> <B>current_postfixop/3:</B>
<DD><A NAME="IDX2949"></A>
<P>
<CODE>current_postfixop(Op, Less, Precedence)</CODE>
<P>
Similar to
<A NAME="IDX2950"></A>
<CODE>current_op/3</CODE>, but it concerns only the postfix operators. It returns <STRONG>only one solution</STRONG>. Not a predicate for general use.
</DL>
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