Re: gnat: float problem

[achrist@easystreet.com]

Jan Prazak wrote:
> 
> I know that floating point numbers are not very exact, but this really
> looks like a bug, because -5.00000E-01 == -0.5.

This  is all fairly reasonable, given that 0.1 cannot be exactly
represented as a floating point on a binary machine.  I believe that
this will be rounded and may be approximated as slighltly more than 0.1.
In hexadecimal, this is 0.199999999... I think, so there is a good
chance that rounding will go upward (50% of the less significant bits
being ones).

Question:  0.5 and -0.5 are decimal numbers that can be represented
exactly as floating point.  Is the compiler required to figure this
out?  If it converted 0.5 to binary the dumb way, ie taking 5 times
0.1, it might not get it right.  Which compilers always get this kind
of conversion correct?

Al