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From: Brian Drummond <brian@shapes.demon.co.uk>
Newsgroups: comp.lang.ada
Subject: Re: Fixed-point question
Date: Sun, 28 Jun 2015 11:39:56 +0000 (UTC)
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Date: 2015-06-28T11:39:56+00:00
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On Sat, 27 Jun 2015 16:42:07 -0400, Bob Duff wrote:

> There's a rule somewhere that says the context has to provide the type
> of the result, so the compiler knows how much precision is needed.  E.g.
> you can say "X := Y * Z;" but not "X := Y * Z * W;".

A rule that surprised me when I first ran into it, but on a moment's 
reflection as a hardware guy, makes perfect sense. It forces you to 
specify the range and resolution of intermediate results, eliminating 
rounding and overflow surprises.

Once I rewrote an algorithm along the lines imposed by this rule, I could 
make it generic and instantiate it with any fixed or floating point type 
I wanted, to investigate its stability and accuracy (with the eventual 
intent of translating to a VHDL implementation using minimal hardware).

-- Brian