Re: Floating point problems in GNAT

[kst@aonix.com (Keith Thompson)]

In <EACHUS.97Feb14115527@spectre.mitre.org> eachus@spectre.mitre.org (Robert I. Eachus) writes:
>    Correct in general, but in Ada there all fixed-point operations
> other than division by an Integer and some type conversions are exact.
> (Of course the Ada rules require implicit or explicit conversion the
> results of multiplying or dividing two fixed-point values, now you
> know why.)  So catastrophic loss of precision can occur, but most
> fixed-point code can be written to avoid loss of precision entirely.

Yes, that's true.  Note, however, that in Ada 95 (unlike Ada 83) the
following is legal:

    A : Duration := 1.0;
    B : Duration := 3.0;
    C : Duration := A / B;

The division operator yields a result of type universal_fixed; the
implicit conversion back to type Duration causes a loss of precision.
As far as the programmer is concerned, this looks like an inexact division
operation on type Duration.

Real arithmetic is tricky.

-- 
Keith Thompson (The_Other_Keith) kst@aonix.com <http://www.aonix.com> <*>
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