sign bit for digits type

sign bit for digits type

[luo]

Subject: sign bit for digits type
Newsgroups: comp.lang.ada
Organization: Cyber Access Internet Communications, Inc.
Summary: 
Keywords: 

I have a float type as follows:

package A is
   type float_32 is digits 6;
end A;

This type is unsigned as defined by the language or the compiler?
I declare an object and a '-' operator as follows to handle negative
numbers:

with A;
package B is
  function "-" (x, y : A.float_32) renames A."-" return A.float_32;
  Real :A.float_32 := -5.0;
end B;

What happens in procedure C when I do the following:
with A;
with B;
procedure C is
  value : A.float_32 := B.Real;
begin
  null;
end C;

What is value equal to, 5.0 or -5.0?
Is this compiler dependent?

TIA.

Re: sign bit for digits type

[Mats Weber]

> This type is unsigned as defined by the language or the compiler?

It is signed as defined by the language, as are all floating point types
in Ada (83 or 95).

Re: sign bit for digits type

[David Taylor]

luo@cybercom.net wrote:
<<snip>> 
> package A is
>    type float_32 is digits 6;
> end A;

> with A;
> package B is
>   function "-" (x, y : A.float_32) renames A."-" return A.float_32;
>   Real :A.float_32 := -5.0;
> end B;
> 
> with A;
> with B;
> procedure C is
>   value : A.float_32 := B.Real;
> begin
>   null;
> end C;
> 
> What is value equal to, 5.0 or -5.0?
> TIA.

You clearly didn't compile this.  The line:

function "-" (x, y : A.float_32) renames A."-" return A.float_32;

has incorrect syntax and also doesn't do what you want it to do.  You need a "unary" minus:

function "-" (x : A.float_32)  return A.float_32 renames A."-";

So, Value should be -5.0. 

Dave Taylor