Quintus arg package

git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@2091 b08c6af1-5177-4d33-ba66-4b1c6b8b522a

library/arg.yap

@@ -0,0 +1,46 @@
+% This file has been included as an YAP library by Vitor Santos Costa, 2008
+
+% it is based on the arg library from Quintus Prolog
+
+:- module(arg,
+	  [
+	   genarg/3,
+	   arg0/3,
+	   genarg0/3,
+	   args/3,
+	   args0/3,
+%	   project/3
+	   path_arg/3
+	  ]).
+
+arg0(0,T,A) :- !,
+	functor(T,A,_).
+arg0(I,T,A) :-
+	arg(I,T,A).
+
+genarg0(I,T,A) :-
+	nonvar(I), !,
+	arg0(I,T,A).
+genarg0(0,T,A) :-
+	functor(T,A,_).
+genarg0(I,T,A) :-
+	arg(I,T,A).
+
+args(_,[],[]).
+args(I,[T|List],[A|ArgList]) :-
+	genarg(I, T, A),
+	args(I, List, ArgList).
+
+args0(_,[],[]).
+args0(I,[T|List],[A|ArgList]) :-
+	genarg(I, T, A),
+	args0(I, List, ArgList).
+
+project(Terms, Index, Args) :-
+	args0(Index, Terms, Args).
+
+% no error checking here!
+path_arg([], Term, Term).
+path_arg([Index|Indices], Term, SubTerm) :-
+	genarg(Index, Term, Arg),
+	path_arg(Indices, Arg, SubTerm).