On 2009/10/11, at 12:59, Frank Schwidom wrote:
> I want to create lists of N unbound elements. If I use the first
> variant:
>
> mklist( 0, []) :- !.
> mklist( N, L) :-
> N2 is N - 1,
> L=[ _| L2],
> mklist( N2, L2)
And your question is? Note that you can also use the SWI-Prolog built-
in predicate length/2 to construct your list. For example:
?- length(L, 7).
L = [_G278, _G281, _G284, _G287, _G290, _G293, _G296].
In other Prolog compilers, length/2, if not a built-in predicate, is
usually available in a library. In my case, the Logtalk implementation
of this library predicate when L is unbound uses the code:
make_list(N, List):-
( N =:= 0 ->
List = []
; M is N-1,
List = [_| Tail],
make_list(M, Tail)
).
(N is guaranteed to be a non-negative integer when make_list/2 is
called)
Cheers,
Paulo
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Paulo Jorge Lopes de Moura, PhD
Assistant Professor
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Home page: <
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Research: <
http://logtalk.org/> Blog: <
http://blog.logtalk.org/>
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