Re: A problem in program

璧甸 wrote:

>Hi, all:
>  
>
Aloha.

>    Now I encounter a problem in programming. Consider the follow program.
>    
>q :-.......    
>    solve_propagate(L,Line1,Line2),!,
>    write('propagate success!'),nl,
>    L = [first|_],
>    write('first = '),write(first),nl,
>    stato_img(CL,CLine1,CLine2,first),
>    ......
>  
>
In the interests of constructing a self contained (similar) example,
consider the following 'list.pl',

    p(1).
    p(2).
    p(3).

    first_p( F ) :-
    bagof( X, p(X), L),
    L = [ F | _ ].

This contrived example has a set of facts about 'p/1' and a predicate to
find the list 'L' of bits that satisfy the predicate. The unification of
an unbound head of the list and an unspecified tail to 'L' seems to have
the desired result as we see in the following session,

    $ gprolog
    GNU Prolog 1.2.18
    By Daniel Diaz
    Copyright (C) 1999-2004 Daniel Diaz
    | ?- [list].
    compiling /home/bancroft/src/prolog/list.pl for byte code...
    /home/bancroft/src/prolog/list.pl compiled, 7 lines read - 759 bytes
    written, 4 ms

    yes
    | ?- first_p(X).

    X = 1

    yes

more,
l8r,
v

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