Re: Math functions in Ada

["John G. Volan" <johnvolan@sprintmail.com>]

> wfrye@mnsinc.com (William Frye) wrote:
> 
> >Is a there a source of freeware Ada routines for simple math functions?
> >I am particularly interested in a routine  to calculate x**y where x and y
> >are floating point numbers.  I am working with gnat on a Win95 platform.

Of course there is such a source! In fact, you already have it! (See
below...)

Jacob S. Rosenberg. wrote:
> 
> Hi William,
> 
> First of all, x**y equals exp(y * log(x)).  So, all you need are the
> log (logarithm) and exp (exponential) functions.  It should be failrly
> easy to write such a function as log and exp are generally provided.
> Indeed, the whole thing would be:
> 
> return exp(y * log(x));
> 
> I strongly recommend that the input values and the functions used are
> of type long_float and not float in order to provide greater range and
> accuracy.  The function itself could return a float.  In that case,
> you can do a conversion to float before the return statement.

Why in heaven's name would you want to re-invent the wheel, when "**" is
already provided in the standard library?  See ARM A.5.1 Elementary
Functions:

  generic
    type Float_Type is digits <>;
  package Ada.Numerics.Generic_Elementary_Functions is
     ...
     function "**" (Left, Right : Float_Type'Base)
       return Float_Type'Base;
     ...

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