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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Saturated Math
Date: Fri, 30 May 2003 13:55:53 -0500
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Date: 2003-05-30T13:55:53-05:00
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Dale Stanbrough wrote in message ...
>I don't like the idea that you have to create a dummy type...
>
>   type Pretend_Type is new Integer range 1..5;
>   package Saturated_Int is new Saturate (Pretend_Type);
>   ...
>
>It seems a bit clunky just to get around the type system. I
>thought of passing in an upper and lower bound to the generic,
>but what type should they be? You could make them integer, but
>what if you wanted saturating integers with a larger range than
>Standard.Integer?


It's mildly annoying that Ada doesn't have a standard name for the
largest range integer type supported by the implementation. (The
standard defines Root_Integer, but it is not a name that you can use in
a program.) But it is easy enough to declare:

    type Largest_Integer_Type is range System.Min_Int .. System.Max_Int;

The, the generic could look something like:

    generic
        Lower_Bound, Upper_Bound : Largest_Integer_Type;
    package Saturated_Math is
       type Saturated_Type is Lower_Bound .. Upper_Bound;
       function "+" (Left, Right : Saturated_Type) return
Saturated_Type;
       ...
    end Saturated_Math;

Using this would be virtually the same as using predefined integer
types. (We use something like this to emulate the target machine's math
in the Janus/Ada compiler. Why do that? We needed it for the Unisys 2200
compiler, as that is a one's complement, 36-bit machine.)

                  Randy.