Re: [boost] fixed pt binary lib

From: Anthony Williams (anthony.ajw_at_[hidden])
Date: 2008-08-01 02:54:24

"John C. Femiani" <john.femiani_at_[hidden]> writes:

> Neal Becker wrote:

>> I have the beginning of a fixed-pt binary lib.  Fixed-pt is popular
>> in DSP applications.  It is integer arithmetic, but keeping track
>> of the binary pt.

> Also, do your implementations for /= and *= actually round? You
> actually seem to be using the round policy for conversions, is that
> right? Have you looked at the numeric/conversion stuff? (I haven't
> grokked it yet).

The division throws away the lower "frac_bits" of the result:

  self operator/=(self const& x) { 
    base_type tmp = (base_type)val / (base_type)x.val;
    val = tmp << (frac_bits);
    return *this; }

I published a more fully-fledged fixed point type here a few months
ago. You can get it from my website (along with a link to the DDJ
article where I describe how it works):

http://www.justsoftwaresolutions.co.uk/news/optimizing-applications-with-fixed-point-arithmetic.html

It has a fixed number if integer and fractional bits (35.28). However,
this allows it to support sin, cos, exp and log by using lookup tables.

Anthony
-- 
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