Re: [eclipse-clp-users] rewritten the default indomain(X, max).?

From: Kish Shen <kisshen_at_...5...>
Date: Tue, 31 Aug 2010 21:09:48 +0100
On 31/08/2010 19:31, mauricio montecinos wrote:


>
> indomain() can be rewritten as:
>
>
>
> choose_val_indomain(Var,Val):-
>
>              get_domain_as_list(Var,Domain),
>
>              mem(Val,Domain).
>
>
>
> mem(X,[X|_]).
>
> mem(X,[_|Xs]):- mem(X,Xs).
>

The actual implementation of indomain/1 in lib(ic) uses low-level 
primitives instead of get_domain_as_list/2 to get the domain, but
what you have should be equivalent.


> I have rewritten indomain(X, max) as:
>
>
>
> choose_val_indomainmax(Var,Val):-
>
>              get_domain_as_list(Var,Domain),
>
>              mem2(Val,Domain).
>
>
>
> mem2(X,[]):-!,fail.
>
> mem2(X,Lista):- maxlist(Lista,X).
>
> mem2(X,Lista):- maxlist(Lista,Y), elimina_elemento(Y,Lista,RLista),
> mem2(X,RLista).
>
>
>
> elimina_elemento(_,[],[]):-fail.
>
> elimina_elemento(X,[X|T],T).
>
> elimina_elemento(X,[H|T],[H|T1]):-elimina_elemento(X,T,T1).
>

Are you trying to remove the selected value from the domain with 
elimina_elemento? The List that elimina_elemento is operating on is not 
the domain itself, so your predicate will not eliminate the value from 
the domain. To eliminate a value from a variable's domain, you need to 
post a constraint. The most general method is to use #\=/2, so you can 
write the equivalent to indomain(X, max) as:

my_indomain_max(X) :-
	get_max(X, V),
	( X = V
	;
	  X #\= V,
	  my_indomain_max(X)
         ).



Cheers,

Kish

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Received on Tue Aug 31 2010 - 20:09:59 CEST

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