Re: Catching NaN .. not a number

[randhol+abuse@pvv.org (Preben Randhol)]

On 5 May 2001 17:46:58 GMT, Staffan Dittmer wrote:
> Did some calcualtions during the night and
> ended up with an output file full of NaN - due to 
> overflow when calculating a factorial.
> 
> A bit surprised by this since I thought a Constraint Error
> would be raised.
> 
> So, how do I catch a NaN result ?

Which compiler? When you say calculating factorial, do you use integer?
If so and If you use GNAT you have to compile your program with this
switch:

   `-gnato'
        Enables overflow checking for integer operations.  This causes
        GNAT to generate slower and larger executable programs by adding
        code to check for both overflow and division by zero (resulting in
        raising `Constraint_Error' as required by Ada semantics).  Note
        that the `-gnato' switch does not affect the code generated for
        any floating-point operations; it applies only to integer
        operations. For floating-point, GNAT has the `Machine_Overflows'
        attribute set to `False' and the normal mode of operation is to
        generate IEEE NaN and infinite values on overflow or invalid
        operations (such as dividing 0.0 by 0.0).

-- 
Preben Randhol ------------------- http://www.pvv.org/~randhol/ --
                 �For me, Ada95 puts back the joy in programming.�