From: Dharmendra Sharma
Subject: Problem with defstruct printing in Common Lisp
Date:
Message-ID: <dsharma.669010518@kaffa>
I would like to be able to print a defstruct object on more than 1
stream i.e. on the screen and to a file. How can I do it with a
predefined :print-function?
Thanx.
--
* Dharmendra ····················@anucsd.anu.edu.AU-post: *
*Computer Science Department, ANU, GPO Box 4, Canberra ACT 2601, Australia *
*From down under | Live to study and not study to live *
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From: Raymond K. Fink
Subject: Re: Problem with defstruct printing in Common Lisp
Date:
Message-ID: <1991Mar15.165013.22368@inel.gov>
In article <·················@kaffa>, ·······@kaffa.anu.oz.au (Dharmendra Sharma) writes:
>I would like to be able to print a defstruct object on more than 1
>stream i.e. on the screen and to a file. How can I do it with a
>predefined :print-function?
>Thanx.
0- Presuming that the :print-function takes a stream argument......
1- First create a stream to the file
2- use (make-broadcast-stream <file-stream> *standard-output*) to create a stream that
will broadcast stuff to multiple streams.
Ray Fink -- Idaho National Engineering Laboratory -- Idaho Falls ID
···@inel.gov 208-526-9323
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In article <·················@kaffa> ·······@kaffa.anu.oz.au (Dharmendra Sharma) writes:
>I would like to be able to print a defstruct object on more than 1
>stream i.e. on the screen and to a file. How can I do it with a
>predefined :print-function?
I have a feeling you're not describing your problem correctly, or you're
very confused.
To print something on more than one stream, you can call PRINT multiple
times, e.g.:
(progn
(print my-object *standard-output*)
(print my-object file-stream))
If you want to print lots of stuff to both streams without having to double
all your PRINT forms, you can use a broadcast stream:
(with-open-stream (bs (make-broadcast-stream *standard-output* file-stream))
(print my-object bs)
...)
The fact that a defstruct type has a :PRINT-FUNCTION is immaterial. The
:PRINT-FUNCTION specifies what the output looks like, but not where it
goes; the stream is a parameter to this function, and that's the only
stream it should perform any output to. It's probably also a bad idea for
a :PRINT-FUNCTION to have *any* side effects other than output to the given
stream; however, CLtL doesn't specifically mention such a restriction (at
least not in the descriptions of :PRINT-FUNCTION and PRINT-OBJECT).
--
Barry Margolin, Thinking Machines Corp.
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