users-prolog
[Top][All Lists]

## Re: Constraining two vectors to be different

 From: LECONTE Jean Michel Subject: Re: Constraining two vectors to be different Date: Tue, 1 Jul 2003 08:50:01 +0200 User-agent: Internet Messaging Program (IMP) 3.0

```try

vectDif([A,B],[C,D]):-
(A#\= C) #\/ (B #\=D ). % means A not equal to C OR B not equal to D

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

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

but here you have to represent a vector as a list of two elements
Jean Michel LECONTE
ENI de Brest

> 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

```