Re: order

[Daniel Diaz]

Hi,

It is not a bug. fd_domain (called by last clause of is_square/1) 
expects 2 integers. If the labeling is done before then X is an integer 
when is_square is called.
If you don't perform the labeling before then X is an FD variable and 
fd_domain throws an exception.

change your clause as follows:

is_square(X) :- Y #>= 1, Y #=< X, X #= Y * Y.

BTW: you use #<=#, #=#,... which perform more propagation but are very 
time consuming. You should consider using #<=, #=,... instead (as done 
above).


Daniel


Le 15/11/2011 22:11, Robert Jäschke a écrit :
> Hello,
>
> When I load the following prolog program:
>
> works(L) :-
>          L = [Z1, Z2],
>          fd_domain(L, 10, 99),
>          fd_prime(Z1),
>          cross_sum(Z1, Z2),
>          fd_labeling(L),
>          is_square(Z2)
>          .
>
> broken(L) :-
>          L = [Z1, Z2],
>          fd_domain(L, 10, 99),
>          fd_prime(Z1),
>          cross_sum(Z1, Z2),
>          is_square(Z2),
>          fd_labeling(L)
>          .
>
>
> cross_sum(X, X) :- X #<# 10.
> cross_sum(X, Y) :- X #># 9, Y1 #=# X rem 10, X1 #=# X // 10,
> cross_sum(X1, Z), Y #=# Z + Y1.
>
> is_square(1).
> is_square(4).
> is_square(9).
> is_square(X) :- fd_domain(Y, 1, X), X #=# Y * Y.
>
>
> I get an error when invoking broken(L):
>
> | ?- broken(L).
> uncaught exception: error(type_error(integer,_#2097948(10..18)),fd_domain/3)
>
> while works(L) gives me results:
>
> | ?- works(L).
>
> L = [79,16] ? ;
>
> L = [97,16] ?
>
> yes
>
>
> The only difference between the two methods is the order of
> fd_labeling(L) and is_square(Z2). To the best of my knowledge the order
> should not matter. Thus, I assume that I hit a bug. Can you confirm this?
>
>
>
> Information about my environment:
>
> > uname -a
> Linux tp 2.6.32-5-amd64 #1 SMP Mon Oct 3 03:59:20 UTC 2011 x86_64 GNU/Linux
> > gprolog --version
> Prolog top-Level (GNU Prolog) 1.4.0
>
>
>
> Best regards,
> Robert


--
Ce message a ete verifie par MailScanner
pour des virus ou des polluriels et rien de
suspect n'a ete trouve.