Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!ucbvax!decwrl!decvax!ima!johnl
From: johnl@ima.ima.isc.com (John R. Levine)
Newsgroups: comp.lang.fortran
Subject: Re: compiling equivalence statements ...
Summary: RTFX3.9-1978
Message-ID: <4129@ima.ima.isc.com>
Date: 30 Jun 89 01:59:20 GMT
References: <2679@cveg.uucp> <4128@ima.ima.isc.com> <14674@ut-emx.UUCP>
Reply-To: johnl@ima.UUCP (John R. Levine)
Distribution: usa
Organization: Segue Software, Inc.
Lines: 26

In article <14674@ut-emx.UUCP> chpf127@ut-emx.UUCP (John W. Eaton) writes:
>In article <4128@ima.ima.isc.com>, (John R. Levine) writes:
>>        dimension stf (12,3)
>>        dimension xstf (12*3)
>>        equivalence (stf,xstf)
>>        equivalence (is1,xstf(3))
>
>Yikes!  There's no need for extra storage here, ...

Extra storage?  Who's using extra storage?  I'm using equivalence statements.
The array xstf exists only so that the compiler will figure out the subscripts
rather than trying to do it manually.

>Also, if is1 is of type integer and stf is of type real, this program
>is not strictly legal, ...

On the contrary, it is entirely legal.  The F77 standard states that real
and integer variables are the same size and you are allowed to equivalence
them together.  The result of storing into a location as an integer and
reading it back as a real is undefined, but so long as you keep your types
straight, it's perfectly legal and portable.  Equivalencing character and
arithmetic types is a different issue, but we've heard plenty about that.
-- 
John R. Levine, Segue Software, POB 349, Cambridge MA 02238, +1 617 492 3869
{ bbn | spdcc | decvax | harvard | yale }!ima!johnl, Levine@YALE.something
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