From dc45cde7ee9e178f1d4826771bfc53470b4503f9 Mon Sep 17 00:00:00 2001
From: vsc <vsc@b08c6af1-5177-4d33-ba66-4b1c6b8b522a>
Date: Wed, 16 Jul 2008 10:34:00 +0000
Subject: [PATCH] flatten does not need to be defined as a system predicate.

git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@2287 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
---
 library/swi.yap | 24 +-----------------------
 1 file changed, 1 insertion(+), 23 deletions(-)

diff --git a/library/swi.yap b/library/swi.yap
index 794aec678..1406b923c 100644
--- a/library/swi.yap
+++ b/library/swi.yap
@@ -64,6 +64,7 @@ swi_predicate_table(_,nth(X,Y,Z),lists,nth(X,Y,Z)).
 swi_predicate_table(_,delete(X,Y,Z),lists,delete(X,Y,Z)).
 swi_predicate_table(_,nth1(X,Y,Z),lists,nth(X,Y,Z)).
 swi_predicate_table(_,memberchk(X,Y),lists,memberchk(X,Y)).
+swi_predicate_table(_,flatten(X,Y),lists,flatten(X,Y)).
 swi_predicate_table(_,member(X,Y),lists,member(X,Y)).
 swi_predicate_table(_,append(X,Y),lists,append(X,Y)).
 swi_predicate_table(_,append(X,Y,Z),lists,append(X,Y,Z)).
@@ -316,26 +317,3 @@ prolog:intersection([_|T], L, R) :-
 prolog:(Term1 =@= Term2) :-
 	variant(Term1, Term2), !.
 
-%%	flatten(+List1, ?List2) is det.
-%
-%	Is true it List2 is a non nested version of List1.
-%	
-%	@deprecated	Ending up needing flatten/3 often indicates,
-%			like append/3 for appending two lists, a bad
-%			design.  Efficient code that generates lists
-%			from generated small lists must use difference
-%			lists, often possible through grammar rules for
-%			optimal readability.
-
-prolog:flatten(List, FlatList) :-
-	flatten(List, [], FlatList0), !,
-	FlatList = FlatList0.
-
-flatten(Var, Tl, [Var|Tl]) :-
-	var(Var), !.
-flatten([], Tl, Tl) :- !.
-flatten([Hd|Tl], Tail, List) :- !,
-	flatten(Hd, FlatHeadTail, List), 
-	flatten(Tl, Tail, FlatHeadTail).
-flatten(NonList, Tl, [NonList|Tl]).
-