Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!quintus!ok
From: ok@quintus.UUCP (Richard A. O'Keefe)
Newsgroups: comp.lang.fortran
Subject: Re: Forced variable declaration
Message-ID: <590@cresswell.quintus.UUCP>
Date: 28 Jan 88 07:00:41 GMT
References: <445@drilex.UUCP> <50500018@uxe.cso.uiuc.edu>
Organization: Quintus Computer Systems, Mountain View, CA
Lines: 32

In article <50500018@uxe.cso.uiuc.edu>, mcdonald@uxe.cso.uiuc.edu writes:
> >I agree.  That's why it's a good idea for FORTRAN programmers  to include 
> >the line IMPLICIT LOGICAL (A-Z) or IMPLICIT CHARACTER (A-Z) in each main  
> >program and subprogram.  Even better, many compilers now make an 
> >IMPLICIT NONE available.  
> 
> You must be kidding! Please, please, don't forget the smiley faces when
> saying things like that! The greatest feature of Fortran over languages
> like C or Pascal (well, C at least, Pascal has so many other stupids) is that
> you don't have to declare variables.

I just got bitten by this today.  Fortunately, I had decided to test a
certain function, and noticed that the relative error was approximately
2.0, when I had hoped for 0.0.  The point of IMPLICIT NONE (which you
don't *have* to use) or UNIX's "-u" flag (which you don'y *have* to use)
is to tell you about this mis-spelled identifiers you hadn't thought of
yet.  Cross-references are fine *IF* you already suspect the problem!
{Best of all are compiler which warn "FOO may be used before it is set"...}

> In any
> case, I and most of the real scientific programmers worry more about 
> typing r(7) where we meant r(8) than typing o(8) where we meant p(8).
> Errors in the mind are much more difficult to find than errors of the
> fingers.

That's why pretty well every programming language except Fortran has
records, and why VAX/VMS Fortran and Fortran 8X *do* have records.
It's also why I never believe the output of any Fortran program I
haven't read.  Come to that, why not use Fortran PARAMETER statements
to help with the r(7) -vs- r(8) problem?

IMPLICIT NONE is the best thing that happened to Fortran since Ratfor.