Re: Question about ordinary fixed point types.

[Stephen Leake <stephen_leake@stephe-leake.org>]

"Peter C. Chapin" <chapinp@acm.org> writes:

> On 2010-08-16 07:02, Stephen Leake wrote:
>
>>> type Angle_Type is delta 0.0005 range -3.1416 .. 3.1416;
>>> Angle : Angle_Type;
>> 
>> Why do you not specify:
>> 
>> for Angle_Type'small use 0.0005;
>
> I don't think I'm too concerned about the actual value of Small used. In
> fact, I'd like to let the compiler choose so that it can optimize the
> code better. Isn't it the case that using a power of two allows for more
> efficient code generation for certain mathematical operations? 

Marginally. The representation is an integer with a scale = 1 /
angle_type'small. The scale is only used when converting to other
numeric types.

> I'm not sure, but I seem to recall reading that somewhere. If that is
> true, then I want that. My machine isn't very fast.

Get it logical first, then optimize.

> My original question wasn't about how to force the type to use a Small
> that I want, rather it was about how can I be sure to visit every value
> of the type in a loop for test purposes.

Then you need to make the loop step by 'Small.

-- 
-- Stephe