Writing to Standard Error from gnu-prolog

From: Roger Clayton (see_at_below.for.email)
Date: 04/27/04

  • Next message: Paul Tarau: "Re: [OT] Prolog for WinCE?" 
    Date: Tue, 27 Apr 2004 16:53:34 +1200

    Hi all,
    Hopefully someone can help with this - here's the problem:
    I need to write messages to the standard error stream
    rather than the standard output from a gnu-prolog program.
    (The program is a component of a compiler for a logic
    programming language).

    Although the gnu-prolog manual is excellent is most cases,
    I am having trouble finding the sequence of builtin
    predicates to make this happen. Here's a few of observations
    I have made so far.

    By consulting the interactive environment the available
    streams can be found as follows:
    ==================
    | ?- current_stream(X), current_alias(X,Y).

    X = '$stream'(0)
    Y = top_level_input ? ;

    X = '$stream'(0)
    Y = user_input ? ;

    X = '$stream'(0)
    Y = debugger_input ? ;

    X = '$stream'(1)
    Y = top_level_output ? ;

    X = '$stream'(1)
    Y = user_output ? ;

    X = '$stream'(1)
    Y = debugger_output

    yes
    ===================

    Because all the output streams are identified by '$stream'(1)
    I suspect that all these are actually the same stream and,
    moreover, none of these are identified as the standard error.

    Setting the stream via the set_output/1 predicate results
    in an existence error for anything but '$stream'(1). Creating
    a new stream via the open/3 or open/4 calls seems to result
    only in a new file being created.

    I hope someone out there has had experience with doing this
    and can steer me in the right direction. Thanks.

    Roger Clayton

    rjc4@ waikato .nz
          cs. .ac

  • Next message: Paul Tarau: "Re: [OT] Prolog for WinCE?"

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