From eb980421a9cd2a008b239ec673b45febd19d1fda Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?V=C3=ADtor=20Santos=20Costa?= <vitor@pekheno.(none)>
Date: Sun, 23 May 2010 18:39:46 +0100
Subject: [PATCH] make term_to_atom/2 a YAP builtin.

---
 docs/yap.tex            |  9 +++++++++
 library/dialect/swi.yap | 11 +----------
 pl/utils.yap            |  8 ++++++++
 3 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/docs/yap.tex b/docs/yap.tex
index b17128f02..0754c76c5 100644
--- a/docs/yap.tex
+++ b/docs/yap.tex
@@ -10886,6 +10886,15 @@ Convert the atom @var{Number} to the difference list of character codes
 @cnindex atom_to_term/3
 Use @var{Atom} as input to @code{read_term/2} using the option @code{variable_names} and return the read term in @var{Term} and the variable bindings in @var{Bindings}. @var{Bindings} is a list of @code{Name = Var} couples, thus providing access to the actual variable names. See also @code{read_term/2}. If Atom has no valid syntax, a syntax_error exception is raised.
 
+@item term_to_atom(?@var{Term}, ?@var{Atom})
+@findex term_to_atom/2
+@syindex term_to_atom/2
+@cnindex term_to_atom/2
+True if @var{Atom} describes a term that unifies with @var{Term}. When
+@var{Atom} is instantiated @var{Atom} is converted and then unified with
+@var{Term}. If @var{Atom} has no valid syntax, a syntax_error exception
+is raised. Otherwise @var{Term} is ``written'' on @var{Atom} using
+@code{write_term/2} with the option quoted(true).
 
 @item read_from_chars(+@var{Chars}, -@var{Term})
 @findex read_from_chars/2
diff --git a/library/dialect/swi.yap b/library/dialect/swi.yap
index dfe875bdf..76958105f 100755
--- a/library/dialect/swi.yap
+++ b/library/dialect/swi.yap
@@ -3,8 +3,7 @@
 % written in an on-demand basis.
 
 
-:- module(system, [term_to_atom/2,
-		   concat_atom/2,
+:- module(system, [concat_atom/2,
 		   concat_atom/3,
 		   setenv/2,
 		   prolog_to_os_filename/2,
@@ -260,14 +259,6 @@ use_foreign_library(A) :-
 	load_foreign_library(A),
 	assert(loaded(foreign_library(A))).
 
-term_to_atom(Term,Atom) :-
-	nonvar(Atom), !,
-	atom_codes(Atom,S),
-	read_from_chars(S,Term).
-term_to_atom(Term,Atom) :-
-	write_to_chars(Term,S),
-	atom_codes(Atom,S).
-
 concat_atom([A|List], Separator, New) :- var(List), !,
 	atom_codes(Separator,[C]),
 	atom_codes(New, NewChars),
diff --git a/pl/utils.yap b/pl/utils.yap
index 820387e31..f7bb1cc6c 100644
--- a/pl/utils.yap
+++ b/pl/utils.yap
@@ -553,6 +553,14 @@ atom_to_term(Atom, Term, Bindings) :-
 	close(Stream),
 	T = Term.
 
+term_to_atom(Term,Atom) :-
+	nonvar(Atom), !,
+	atom_codes(Atom,S),
+	read_from_chars(S,Term).
+term_to_atom(Term,Atom) :-
+	write_to_chars(Term,S),
+	atom_codes(Atom,S).
+
 simple(V) :- var(V), !.
 simple(A) :- atom(A), !.
 simple(N) :- number(N).