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## Constraining two vectors to be different

 From: Thomas Bourdeaud'huy Subject: Constraining two vectors to be different Date: 30 Jun 2003 19:13:54 +0200

```Hi, I'm using the FD solver,
and  try to define the predicate allDiferent(List_Of_Vectors)
I use this predicate not to verify that all the vectors are different,
but to constrain the variables of these vectors not to allow them to be
equals...

I know that \= and #\=# exist, but i defined :

vectDif(E1,E2):-
\=(E1,E2).

notIn(_,[]):-!.
notIn(E,[E1|List]):-
vectDif(E,E1),
notIn(E,List).

tousDif([_]):-!.
tousDif([E|List]):-
notIn(E,List),
tousDif(List).

And tested :

tousDif([[1,2],[3,4]]).
yes

tousDif([[1,2],[X,4]]).
yes

tousDif([[1,2],[X,2]]).
no

The last result is not the one i needed : i just wanted to make X <>
1...

If I use  #\= or #\=# in the definition of vectDif, the results are :

tousDif([[1,2],[3,4]]).
uncaught exception: error(type_error(fd_evaluable,[1,2]),(#\=)/2)

tousDif([[1,2],[X,4]]).
uncaught exception: error(type_error(fd_evaluable,[1,2]),(#\=)/2)

What's wrong with my implementation ? Is there a 'dif' function in GNU
Prolog ?

Thanks,

Thomas Bourdeaud'huy
Ecole Centrale de Lille

```

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