Re: How to use "infinite" ?

[Reinert Korsnes <reinert.korsnes@chello.no>]

Gautier Write-only wrote:

> Dmitry A. Kazakov:
> 
>> You should define an abstract data type to represent the set of integer
>> numbers + ideals you want (such as "negative infinity", "positive
>> infinity") . For example a universal package could be generic:
>> 
>> generic
>>    type Finite_Integer is range <>;
>> package Integers_With_Infinity_Ideals is
>>    type Infinite_Integer is private;
>>    --
>>    -- Unary operations
>>    --
>>    function "+" (Left : Infinite_Integer) return Infinite_Integer;
>>    function "-" (Left : Infinite_Integer) return Infinite_Integer;
>>    --
>>    -- Dyadic operations
>>    --
>>    function "+" (Left : Finite_Integer; Right : Infinite_Integer)
>>       return Infinite_Integer;
> [...]
> 
> Great idea, you just drafted a (or the first ?) computer package for
> nonstandard analysis!
> 
> I strongly suggest to use the (hem...) standard wording of nonstandard
> analysis for the types (unlimited, infinitesimal, etc.).

:-)

well, for my limited "hack-programming" I would
like to replace the following with something simpler:

if a /= Integer'Last and b /= Integer'Last then
   if a >  a + b then
      a := a + b;
   end if;
end if;

I tried to represent "infinite" with Integer'Last -
directly from the mathematical specification/problem formulation 
given. Maybe it is not a good idea.

Note, by the way, that the construct above
may be rather ugly if a and b are complex expressions....

reinert


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