Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!ut-emx!chpf127
From: chpf127@ut-emx.UUCP (John W. Eaton)
Newsgroups: comp.lang.fortran
Subject: Re: compiling equivalence statements ...
Summary: No need for extra storage!
Message-ID: <14674@ut-emx.UUCP>
Date: 29 Jun 89 19:31:01 GMT
References: <2679@cveg.uucp> <4128@ima.ima.isc.com>
Distribution: usa
Organization: The University of Texas at Austin, Austin, Texas
Lines: 44

In article <4128@ima.ima.isc.com>, (John R. Levine) writes:
> In article <2679@cveg.uucp>, (Scott Alan Stuff) writes:
> >       dimension stf (12,3)
> >       equivalence (is1,stf(3))
> 
> This is a wart in F66 that they took out of F77, although most F77
> compilers continue to accept it.  In F66 equivalence statements you
> could either give a normally subscripted reference or you could use
> a single subscript and it would act as though it was a singly
> dimensioned array of the same size.  To make it work, try something
> like this:
> 
>        dimension stf (12,3)
>        dimension xstf (12*3)
>        equivalence (stf,xstf)
>        equivalence (is1,xstf(3))

Yikes!  There's no need for extra storage here, since stf(3) (if it
actually was a singly subscripted array) is guaranteed to be the same
as stf(3,1).  Assuming that this is what the original programmer
intended,% just use

      dimension stf(12,3)
      equivalence ( is1, stf(3,1) )

Also, if is1 is of type integer and stf is of type real, this program
is not strictly legal, but will probably work on many machines that
use the same number of bits for integer and real variables.  If you
get the thing to compile and it gives you mysterious results, this may
be the source of some of your errors.


% If this is not what was intended, you've probably got a bigger mess
  on your hands than you realize :-).


P.S. to Scott:  I tried to send mail to you but it just bounced back.

-- 
John Eaton
chpf127@emx.utexas.edu
Department of Chemical Engineering
The University of Texas at Austin
Austin, Texas  78712