Re: Fixed-point question

[Brian Drummond <brian@shapes.demon.co.uk>]

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