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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: fixed point types over an interface
Date: 1997/02/07
Message-ID: <dewar.855364096@merv>#1/1
X-Deja-AN: 215272924
references: <32FBB550.41C67EA6@efogm.msd.ray.com>
organization: New York University
newsgroups: comp.lang.ada
Date: 1997-02-07T00:00:00+00:00
List-Id: <comp.lang.ada>


Allen Krell said

<<With Ada83, is it safe to assume that two different
compilers will store a fixed point type in the same way?

For example

Two processors are communicating over an interface.  The
applications for each processor are written/compiled
using compilers from two different vendors.

If each application has

type FX_PT_TYPE is delta .001 range -100 .. +100;
Variable : FX_PT_TYPE := 1.345;

Will the binary representation of 'Variable'
be the same with both compilers?>>


The answer for both Ada 83 and Ada 95 is certainly not. As with all
data in the absence of rep clauses, there is lots of freedom for 
a compiler to decide how to store the data. In particular for fixed-point
some compilers will use the largest Small possible, and others will
use the smallest Small possible. 

To pin this down, you need to use a Small clause and a Size clause,
then you should be pretty safe relying on the result, although one
can imagine compilers doing weird things.