NetNews Usenet Archive 1992 #18/NN_1992_18.iso/spool/comp/lang/fortran/3035

Internet Message Format | 1992-08-14 | 1.8 KB

Path: sparky!uunet!elroy.jpl.nasa.gov!ames!haven.umd.edu!mimsy!afterlife!adm!aos!lapoint
From: [e-mail] (Claude LaPointe )
Newsgroups: comp.lang.fortran
Subject: RE: programming style question
Message-ID: <[e-mail]>
Date: 14 Aug 92 12:25:59 GMT
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Nntp-Posting-Host: adios.brl.mil


[e-mail] (Dave Tholen) writes:


  >  A question about programming style:  How many of you explicitly OPEN
  >  preconnected units, which nowadays usually mean standard input, standard
  >  output, and sometimes standard error (typically units 5, 6, and 0)?  In
  >  the old days, 5 and 6 were often card reader and printer.  I haven't
  >  been doing so myself, but the question came up recently because I've
  >  ...


Given that 0,1,2,5,6 and probably others are highly non-portable
ways of addressing standard in, out, and error. It is better not to
use them.

Because the 77 standard didn't much consider the kinds of output
capabilities now available, it didn't address standard error,
so there is no choice but to use a unit number - however it should
be done with the realization that porting may require a change in the
value. That is, isolate its use as much as possible in a subprogram
and define it with a parameter statement.

With respect to standard in & out use "*" which must not appear in
OPEN and CLOSE statements.

Some time ago, an objection was raised to this on the basis that the
"*" must be present at compile time, and so cannot be passed as an
argument. Actually, it can, but clumsily. When the intent is to write
to standard out, set the calling argument not to "*" but to some
negative integer. Similarly for input.


      subroutine out (unit)
      integer unit
      ...
      if (unit.lt.0) then
         write (*,...
      else
         write (unit,...
      endif
      ...