Re: Ada function sqrt(x)

[kst@thomsoft.com (Keith Thompson)]

In <51o7nh$5vl@cf01> pascal.obry@der.edfgdf.fr (Pascal Obry) writes:
> "zeppelin" <zeppelin@access.mountain.net> wrote:
> 
> >I want to find the sqrt of a interger... how can I do this and what package
> >do I need to declare
[...]
> If you are using Ada95 then the package is
> 
> Ada.Numerics.Generic_Elementary_Functions or
> Ada.Numerics.Elementary_Functions (for a float instanciation).

The original question was about finding the square root of an *integer*;
Generic_Elementary_Functions and its instantiations work on floating-point
types.

You can convert the argument to a floating-point type, take the square
root, and convert back to an integer type, but that may lose precision
in some cases.  Also, I think an integer square root operation typically
truncates rather than rounding (for example, sqrt(99) is 9, not 10).
Ada 95 provides a 'Truncation attribute (see RM95-A.5.3) -- but again,
watch out for loss of precision (sqrt(9.0) *might* return something like
2.9999999; also, many 32-bit integers cannot be represented exactly in
32-bit floating-point).

You might have better luck writing an integer sqrt function that only
uses integer arithmetic.  I'm sure this has been done before; perhaps
someone else knows where.

-- 
Keith Thompson (The_Other_Keith) kst@thomsoft.com <*>
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