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From: johnherro@aol.com (John Herro)
Subject: Re: Calculating SQRT in ADA
Date: 1999/03/24
Message-ID: <19990324125518.01416.00000432@ngol08.aol.com>#1/1
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Newsgroups: comp.lang.ada
Date: 1999-03-24T00:00:00+00:00
List-Id: <comp.lang.ada>

Here's a generic square root routine in Ada 83, taken from my AdaTutor program:

generic
  type Dummy is digits <>;
function Sqrt(X :in Dummy) return Dummy;
function Sqrt(X :in Dummy) return Dummy is
  Guess : Dummy := X;
begin
  if X < 0.0 then
    raise Constraint_Error;
  end if;
  while X /= 0.0 and then
       abs(Guess*Guess/X - 1.0) > 3.0*Dummy'Epsilon loop
    Guess := (X/Guess + Guess) * 0.5;
  end loop;
  return Guess;
end Sqrt;

I tested this routine with Vax Ada 83, which has types Float, Long_Float, and
Long_Long_Float.  That last type gives at least 33 decimal digits of precision.
 I instantiated this function, as well as Text_IO.Float_IO, for all three
types.  When I tested with the three types, all displayed digits of the answers
were correct.  I hereby place this long and complex function :-) into the
public domain.  Enjoy.
- John Herro
You can download a shareware AdaTutor program at
http://members.aol.com/AdaTutor