Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!samsung!munnari.oz.au!goanna!ok
From: ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe)
Newsgroups: comp.lang.fortran
Subject: Re: Fortran vs. C for numerical work (SUMMARY)
Message-ID: <4450@goanna.cs.rmit.oz.au>
Date: 6 Dec 90 08:41:05 GMT
References: <1990Nov21.220816.15220@rice.edu> <2173@tuvie> <1990Dec3.191100.22176@ariel.unm.edu>
Organization: Comp Sci, RMIT, Melbourne, Australia
Lines: 42

In article <1990Dec3.191100.22176@ariel.unm.edu>, john@ghostwheel.unm.edu (John Prentice) writes:
> In article <4421@goanna.cs.rmit.oz.au> ok@goanna.cs.rmit.oz.au (Richard A. O'Keefe) writes:
> >In article <1990Nov30.183032.5420@ccu.umanitoba.ca>, salomon@ccu.umanitoba.ca (Dan Salomon) writes:
> >> The problem
> >> was that the FORTRAN procedure accepted arrays with not only any size
> >> of dimensions, but also with any number of dimensions.

> >I don't recall that being legal in F77.  To be sure, I've met compilers
> >that didn't bother to check, and I think there was a special case for
> >DATA statements, but argument passing?

> Assuming I am reading the original posting correctly, there is nothing
> to preclude this in Fortran.  Specifically, imagine the following code:
>       real*8 a
>       pointer (a,ipnt)		<========================

My question was specifically about F77, by which I meant the 1978 ANSI
Fortran standard.  "pointer" is not part of that language.

I have seen some disgusting stuff in the Harwell library where the
programmers did

	REAL X(N)
	CALL FOO(X(1), X(3), ...)

and FOO used the first argument as a pointer to the beginning of an array,
and the *difference* between the second argument and the first as the
"stride" between array elements.  That meant that you could do

	CALL FOO(M(I,1), M(I,2), ...)
	CALL FOO(M(1,I), M(2,I), ...)

FOO, of course, had been coded in assembler.  I had the extremely unpleasant
task of trying to port a program using this stuff to a B6700, where there
wasn't any assembler, nor was there any hardware support for subtracting
pointers.  The question stands:  is passing a scalar (D=0) or an array
taking D subscripts to a subprogram expecting an array taking E.ne.D
subscripts legal in standard Fortran 77?

-- 
The Marxists have merely _interpreted_ Marxism in various ways;
the point, however, is to _change_ it.		-- R. Hochhuth.


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