Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!unmvax!ogccse!mwolfe
From: mwolfe@ogccse.ogc.edu (Michael Wolfe)
Newsgroups: comp.lang.fortran
Subject: Zero vs. One trip loops ... correction
Summary: Fortran-77 didn't REALLY break the -66 STANDARD
Message-ID: <4513@ogccse.ogc.edu>
Date: 1 Sep 89 14:31:09 GMT
References: <1073@cernvax.UUCP>
Reply-To: mwolfe@cse.ogc.edu (Michael Wolfe)
Organization: Oregon Graduate Center, Beaverton, OR
Lines: 20


for future reference, the real Fortran-66 standard did specify that all
loops would 'trip' at least once.  It also specified that the loop upper
limit MUST BE GREATER THAN OR EQUAL TO the loop lower limit.  Thus, the
loop:
    N = 0
    DO 10 I = 1,N
10  CONTINUE
which trips zero times in Fortran-77, is NOT 'STANDARD-CONFORMING' according
to Fortran-66.  So, Fortran-77 did not break 'one-trip' loops, it only
defined what to do when the upper limit was less than the lower limit.

Fortran-66 did define different semantics for loop iteration processing,
and most (or for all I know, all) Fortran-66 implementations would allow
the above loop and would trip once.  So the implementations were
incompatible, but the standards weren't.

Just goes to show how few people read the -66 standard.

It's also interesting to see how small the -66 standard is, compared to the -77.