Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!ukma!uflorida!haven!uvaarpa!hudson!bessel.acc.Virginia.EDU!gl8f
From: gl8f@bessel.acc.Virginia.EDU (Greg Lindahl)
Newsgroups: comp.lang.fortran
Subject: Re: i++, i+=1, i=i+1
Message-ID: <561@hudson.acc.virginia.edu>
Date: 16 Sep 88 17:52:47 GMT
References: <3976@h.cc.purdue.edu> <3659@lanl.gov>
Sender: news@hudson.acc.virginia.edu
Reply-To: gl8f@bessel.acc.Virginia.EDU (Greg Lindahl)
Organization: Dept. of Astronomy, University of Virginia
Lines: 21

In article <3659@lanl.gov> jlg@lanl.gov (Jim Giles) writes:
>
> [stuff deleted]
>
>No, it doesn't cause the subscript to be evaluated twice.  In Fortran
>functions are not allowed to have side effects.  The compiler will
>therefore recognize the subscript expressions as common subexpressions
>and will evaluate only once. [...]
>

VAX/VMS fortran doesn't work this way, even with math library functions
which are known to have no side-effects. if you write

	a = sin(x)
	b = sin(x)
	c = sin(x)

it will call sin() 3 times. anyone have any idea why they would do this?

Greg Lindahl                              internet:  gl8f@virginia.edu
U Va Dept. of Astronomy                   bitnet:    gl8f@virginia.bitnet