Re: Users-prolog Digest, Vol 32, Issue 1

[Duncan Patton a Campbell]

On Mon,  5 Sep 2005 10:01:54 -0600 (MDT)

I haven't had much luck with the open/4(.,.,.,Options) syntax myself.
Instead I use open/3 and set_stream_type/2.

Dhu


[]
> Hi, 
> 
> I'd like some help trying to understand the use of streams. As I understand, 
> this should produce a file 'out.txt', with the listing in it. However, the 
> listing gets printed to the screen, and the file is empty:
> 
> | ?- open('out.txt', write, H, [alias(out)]), current_output(COUT), 
> set_output(out), listing, set_output(COUT).
> 
> squint([], []).
> squint([A|B], [C|D]) :-
>  integer(A),
>  C is A * A,
>  squint(B, D).
> squint([A|B], [A|C]) :-
>  squint(B, C).
> 
> COUT = '$stream'(1)
> H = '$stream'(2)
> 
> (1 ms) yes
> | ?-
>  
> If anyone has any ideas, suggestions, anything, please reply.
> Thanks and have a great weekend.
> Cliff
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> Message: 3
> Date: Mon, 05 Sep 2005 16:05:45 +0200
> From: A-S Saidi <address@hidden>
> Subject: Re: streams
> To: Cliff Bender <address@hidden>
> Cc: gprolog <address@hidden>
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> ------------------------------
> 
> Message: 4
> Date: Mon, 05 Sep 2005 11:18:16 -0400
> From: Vic Bancroft <address@hidden>
> Subject: Re: streams
> To: Cliff Bender <address@hidden>
> Cc: gprolog <address@hidden>
> Message-ID: <address@hidden>
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> 
> Cliff Bender wrote:
> 
> >I'd like some help trying to understand the use of streams. 
> >
> Hurrms, not sure what is broken w/ your example, however, I tend to use 
> the format construct.
> 
>     $ gprolog
>     GNU Prolog 1.2.18
>     By Daniel Diaz
>     Copyright (C) 1999-2004 Daniel Diaz
>     | ?- assertz(p(1)), assertz(p(2)).
> 
>     yes
>     | ?- open('out.log', write, H), (p(X), format(H, "p(~w) ~n", [X]),
>     fail; close(H)), !.
> 
>     H = '$stream'(2)
> 
>     (1 ms) yes
>     | ?- system('cat out.log').
>     p(1)
>     p(2)
> 
>     (1 ms) yes
> 
> This explicit indication of the target stream is useful in context where 
> there is more than one and it also gives you more control over what is 
> sent to the stream . . .
> 
> more,
> l8r,
> v
> 
> -- 
> "The future is here. It's just not evenly distributed yet."
>  -- William Gibson, quoted by Whitfield Diffie
> 
> 
> 
> 
> 
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