Path: utzoo!mnetor!uunet!husc6!hao!gatech!uflorida!codas!novavax!hcx1!hcx2!bill
From: bill@hcx2.SSD.HARRIS.COM
Newsgroups: comp.lang.fortran
Subject: Re: F8X: MODULE vs. INCLUDE (really
Message-ID: <44400018@hcx2>
Date: 18 Mar 88 13:48:00 GMT
References: <5947@ames.arpa>
Lines: 39
Nf-ID: #R:ames.arpa:5947:hcx2:44400018:000:2223
Nf-From: hcx2.SSD.HARRIS.COM!bill    Mar 18 08:48:00 1988


> I'm sorry, I could have been a great deal clearer.  My point is that the
> "dependency" on previously compiled MODULEs is the same as that of 
> INCLUDE files with the addition of one more check - that the source code
> of the module has not been modified since the module was compiled.  In
> the implementations of modules with which I am familar (HP Modcal, Turbo
> Pascal Release 4.0), the compiled form of the module resides in a separate 
> file from the source, so the regular file system modification dates provide 
> the information to ensure that the compiled form is not out of date relative 
> to the source code of the MODULE.  With that one additional check, the 
> dependencies introduced by USE are exactly those of INCLUDE.

I agree, Carl, that the "dependency" is the same, but I believe there is
danger here in that the compilation system is now leading the user on into
a false sense of security.  The tendency (particularly with Ada now becoming
popular) will be for users to believe that now that the compiler _can_
check the dependency, it will.  WRONG!!!  First, there is no requirement
in the standard that it do any such checking.  Second, your proposed method
for checking the dependency leaves out a very important safety check:
How do you know that two independently-compiled routines that USE the same
MODULE were compiled with the same version?  This cannot be checked until
link-time, because that is the first you have any clue that these two
routines are part of one program.  That is a much higher burden on the
compilation system than simply checking a revision date of a file at
compile-time.

I don't assert that INCLUDE is any safer, better, or more powerful than
MODULE.  I only assert that it is such a widespread extension to FORTRAN
that it should be standardized in 8x.  As for MODULE, I think it is 
dangerous in its present form (because no checks are required), and I
think that requiring the checks would impose too much burden on a compiler
for a language that is supposed to compile fast and run fast.  Given
those opposing requirements, I think MODULE should be deleted.

Bill Leonard
Member, X3J3
Harris Computer Systems Division
Fort Lauderdale, FL
bill@ssd.harris.com