Hi Graham,
trying to compare two doubles which are equal
and isn't passing within c++ like so  why is this
any ideas ,
Thanks

val = 0.005000
valb = 0.01000
if (2.*val == valb)
{
 return true;
}
valA=0.010000
valb=0.010000


Yes ... you should never compare floats (or even doubles) to see if they're equal in C or C++ - because of routing errors.  Internally, floating point types are held only to a certain accuracy and so "issues" creep in.

A float example:

Take the value 1.0
Divide it by 3.0 ... and you get 0.3333333
Multiply it by 3.0  and yoiu get 0.9999999
which is NOT equal to 1.0

thanks for that , so whats the work around  in the above example to see if they are equal  

It depends on what you're doing;  sometimes you'll find that integers rather than floats would have been better in the first place, and at other times you might subtract one value from the other and see if the absolute value of the result is less that a threshhold.

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