Reading from files?

[carlos calderon]

HI all,

 

As I said in some of my previous e-mails I am new to Prolog and GNU-Prolog and therefore I apologise if some of the questions are too simple or just completely nonsense.

 

I am having problems with what I think is a simple thing: reading from files.

 

go(X,Y) :-

            solve(X,Y),

            write2file(X,Y).

 

 

solve(X,Y) :-

            /*Vars, domains and constraints are defined here*/

            /*it works fine no problem*/

 

write2file :-

    open('/home/carlos/gnu_prolog/example/files/test.txt', append, Out,[]),

    write_term(Out,X,[]),

    write_term(Out,Y,[]),

    close(Out,[force(true)])./*to be sure that the stream is closed*/

 

>> with this I got the following:

111213182122272831363738464748565758656667687176777881828788

>>all the possible solutions i.e X=1 Y=1 is the first one

>>Great!! ;-)))

 

Then I want to read this file 'test.txt'

Ideally, every time a solution is written to test.txt I would like to have access to it and read it.

 

So I did the following:

 

 

go(X,Y) :-

            solve(X,Y),

            write2file(X,Y),

            read_file_to_list(Result).

write2file :-

    open('/home/carlos/gnu_prolog/example/files/test.txt', append, Out,[]),

    write_term(Out,X,[]),

    write_term(Out,Y,[]),

    close(Out,[force(true)])./*to be sure that the stream is closed*/

 

read_file_to_list(Array) :-

      open('/home/carlos/gnu_prolog/example/files/test.txt', read, In,[type(text)]),

       set_input(In),

        set_stream_buffering(In,none),

        get_char(In,Char),

        (Char = end_of_file

                -> Array=[]

        ;

                Array = [Char | T],

                read_file_to_list(T)

       ),

    close(In).

 

>>I get the following result:

in my text file:

11

>>just the first solution

>>and the following error:

uncaught exception: error (resource_error(too_many_open_streams), open/4)

pag 40 in the manual.

any ideas about what it's happening?

 

I guess, my real question is: is there any "standard" method to read files?

 

again, sorry for the simplicity but if I don't ask stupid questions I remain stupid.

 

I have also tried to use I/O to constant terms.

 

go(X,Y) :-

            solve(X,Y),

            write2chars(X,Y).

 

write2chars(X,Y) :-

            write_to_chars([X|L1],X),

            write_to_chars([X|L1],Y),

            read_from_chars([X|L1],_A),

            read_from_chars([X|L1],_A),

            set_output(user_output),

            put_char(_A),

            put_char(_B).

 

>>This time I get an empty test.txt and a no to my query go(X,Y).

 

My final objective is to have a precise control over the streams (have a clear understanding first) for communication purposes (sockets).

 

As far as my understanding goes there are no tutorials or examples on web but if anyone knows of any please, I would be very grateful if he/she lets me know.

 

Thanks for the help