Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!rochester!uhura.cc.rochester.edu!ur-valhalla!chan
From: chan@galaxy.ee.rochester.edu (Daniel Chan)
Newsgroups: comp.lang.pascal
Subject: Re: DUEL OUTPUT
Message-ID: <1868@valhalla.ee.rochester.edu>
Date: 5 Mar 89 05:32:37 GMT
References: <18461@adm.BRL.MIL> <1265@sdcc15.ucsd.edu>
Sender: usenet@valhalla.ee.rochester.edu
Reply-To: chan@ee.rochester.edu (Daniel Chan)
Organization: UR Dept. of Electrical Engg, Rochester NY 14627
Lines: 84

>From: pa1804@sdcc15.ucsd.edu (pa1804)
Date: 4 Mar 89 23:41:57 GMT
Organization: University of California, San Diego

>In article <18461@adm.BRL.MIL>, pmancini@lynx.northeastern.edu writes:
> 
> 		I would like to know what is (if possible) standard
> 	implementation in PASCAL to send text output simultaneously
> 	to the screen and to a LST device or file.  I hate having to
> 	write lines twice, such as;
> 
> 	writeln('abcdefg12345');   {goes to screen}
> 	writeln(lst,'abcdefg12345');  {goes to printer}
> 
> 		Is there anyway I can send the output to both without
> 	writing the line twice?  In programs which print a lot of text
> 	to the screen and the printer it gets very tedious typing everything
> 	over and over again.


!	You can write a procedure that will send the output to both
!	the screen and the other output device:
!
!
!
!
!	Procedure WriteAll { pass variables that are necessary }
!
!	Begin  { WriteAll }
!	 
!	  writeln(argument);  { this goes to the screen }
!
!	  writeln(OutputDevice1, argument); 
!	    { this goes to OutputDevice1 }
!
!	  writeln(OutputDevice2, argument);
!	    { this goes to OutputDevice2}
!
!	end;   { WriteAll }
!
!        ..
!	..
!	..
!	..
!
!	begin { main program }
!
!	  ..
!	  ..
!	  WriteAll;  ( variables )
! 	  ..
!	  ..
!	end.  { main program } 
!
!
!
!
!	As you can see, by using the procedure WriteAll you can
!	send output to as many destinations as you want.
!
!
!
!						George Chen
!
!        pa1804@sdcc15.UCSD.EDU    PO BOX 4474  La Jolla, CA 92037

The problem is not that simple when you have something like:

   writeln ("abcdefg34"); writeln (345, "abcd"); writeln ("345", 1.2E-3);

It's also very painful to create a procedure for each combination of
arguments you want to write.

You need a function (like sprintf in C) that takes arguments like write/writeln
and returns a string of what the output looks like.  You can then use that
string as an argument to WriteAll.  This method is slightly less painful than 
duplicating every write/writeln.  It works even better if you want your output
to go to more than two places.

Also there was a posting couple of days ago about logging both input and output.

Hope all these will help.

-dan.