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From: eachus@spectre.mitre.org (Robert I. Eachus)
Subject: Re: Constants vs Functions (was Re: Optimizing recursion...)
Date: 1998/08/27
Message-ID: <EACHUS.98Aug27155342@spectre.mitre.org>#1/1
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Organization: The Mitre Corp., Bedford, MA.
Newsgroups: comp.lang.ada
Date: 1998-08-27T00:00:00+00:00
List-Id: <comp.lang.ada>

In article <6s43nq$m31$1@berlin.infomatch.com> blaak@infomatch.com (Ray Blaak) writes:

 > This is a sound suggestion, but one problem with it is that such constants
 > tend to be used to define ranges, array sizes, etc. If it is not a constant
 > then the static property is lost, and things like compile-time fixed-sized
 > arrays, and constraint check elimination become difficult.

   There are two issues here, one is that there are places where Ada
requires values which meet the reference manual definition of static.
In those cases, you have to follow the rules of RM4.9, which in Ada 95
do permit function calls, but nothing like this.  Of course the only
two cases where you are ever likely to run into this issue are in the
declarations of scalar numeric types and in representation
clauses. (Note that I am being tricky there.  It really is the
parameters which determine the base type which must be static

   The second case, which is much more common, is where the language
rules will define an expression to be non-static, but decent Ada
compilers will do the optimizations IF you have the pragma there (and
optimization turned on).  Try it and see.
--

					Robert I. Eachus

with Standard_Disclaimer;
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function Message (Text: in Clever_Ideas) return Better_Ideas is...