Path: utzoo!mnetor!uunet!hpda!hpesoc1!hpcllla!hpclisp!hpclcdb!cdb
From: cdb@hpclcdb.HP.COM
Newsgroups: comp.lang.fortran
Subject: Re: Semantics of local variables
Message-ID: <6690007@hpclcdb.HP.COM>
Date: 2 Jan 88 05:36:10 GMT
References: <2617@killer.UUCP>
Organization: HP ITG/ISO Computer Language Lab
Lines: 22


> A quick question for serious FORTRAN user's: do the semantics of initializing
> a local variable in a DATA statement force the variable to have static 
> scope? That is, can you generally count on the variable retaining its value
> across calls to the subroutine in which it's defined? I know this is the case
> for some compilers, but can you count on it generally? F77 and no, I don't 
> have a copy of the standard.
> 

  The Fortran 77 standard says that you can't depend on it (Page 8-11, lines
33-42, if you want to look it up).  As a practical matter, the compiler would
have to go to a lot of trouble and produce a lot of extra code to break this
assumption - I've only heard rumors of one compiler that didn't make these 
values saved.  It supposedly did/does assignments to the initialized locals
to implement DATA, thereby trashing any previously changed values - and
slowing down the program unnecessarily.

  Given the availability of the SAVE statement in standard F77, why worry -
SAVE it!

						Carl Burch
						hplabs!hpda!cdb