Re: Generic_Rational

[Simon Wright <simon@pushface.org>]

hnptz@yahoo.de writes:

> On http://rosettacode.org/wiki/Arithmetic/Rational/Ada there is an
> Ada-package which is OK as it is. It says that the package can be
> instantiated with any integer type. However, I tried to instantiate it
> with Long_Integer.

And the instantiation compiles fine.

> I also used Ada.Numerics.Long_Elementary_Functions. 

There was no need for that.

> Now, the Test_Rational programm does not work anymore. The function
> "/" is perhaps not in compliance with Long_Integer. I wonder if the
> declarative part in Test_Rational has a false effect.
>
> What are your suggestions to make it working for Long_Integer numbers
> as well?

When the test program says

   for Candidate in 2..2**15 loop

Candidate is of type Integer (see ARM 3.6(17..18)[1], so that when it
says

         Sum  : Rational := 1 / Candidate;

there would need to be a function

   function "/" (L, R : Integer) return Rational

but the only "/" that returns Rational and takes integer types takes
Long_Integers.

Recast the loop as

   for Candidate in Long_Integer'(2)..2**15 loop

or

   for Candidate in Long_Integer range 2..2**15 loop

and now there's a similar problem with

         for Divisor in 2..Integer (Sqrt (Float (Candidate))) loop

...

[1] http://www.ada-auth.org/standards/rm12_w_tc1/html/RM-3-6.html#p17