Re: see/seen, tell/told

Hi Antonio,

tell/1 and friends are obsolete beasts. If you want a portable code 
(across Prolog systems) you should use ISO predicates (e.g. open/3-4 ...).

Daniel


Antonio Maschio wrote:
> Hi folks,
>
> Well, I know these statements are outdated, but please, consider this 
> code:
>
> %-----------------
> go :-
>     tell('aaa'), writeq('First line of ''aaa'''),  write('.'),nl,
>     tell('bbb'), writeq('First line of ''bbb'''),  write('.'),nl,nl,
>     tell(user),  writeq('This goes on the screen'),write('.'),nl,
>     tell('aaa'), writeq('Second line of ''aaa'''), write('.'),nl,nl,
>     told.
>
> goread :-
>     see('aaa'), read(X1),
>     see('bbb'), read(X2),
>     see(user),  write('Type something, end with dot: '), read(X3),
>     see('aaa'), read(X4),
>     seen,
>     write(X1),nl,
>     write(X2),nl,
>     write(X3),nl,
>     write(X4),nl.
> %-------------------
>
> When executed under yap (go/1 first and then goread/1), it returns:
>
> Type something, end with dot: jrjkerjt.
> First line of 'aaa'
> First line of 'bbb'
> jrjkerjt
> First line of 'aaa'
> yes
>
>
> SWI-prolog and gprolog return instead:
>
> % Swipl
> Type something, end with dot: djkjhrt.
> First line of 'aaa'
> end_of_file
> djkjhrt
> Second line of 'aaa'
> true.
>
> %gprolog
> Type something, end with dot: dksjdhf.
> First line of 'aaa'
> end_of_file
> dksjdhf
> Second line of 'aaa'
>
> (1 ms) yes
>
> It seems that both swipl and gprolog keep the same file pointer for 
> aaa and for bbb, which should instead be two different sources each 
> with its pointer.
>
> I'm not a prolog programmer (not yet). I just try pieces of code to 
> understand the working of the prolog engine, and if the code I pasted 
> is not correct, or if it may be written in a better (and satisfactory) 
> way, please tell me.
>
>
>
> --------------------------
> Antonio Maschio
> <tbin at libero dot it>
>
>
>
>
>
> _______________________________________________
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> [email protected]
> http://lists.gnu.org/mailman/listinfo/users-prolog
>


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