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wolf99/my_isnan.c

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Portable alternative to isnan() in math.h
Raw
my_isnan.c
int my_isnan(double x)
{
volatile double tmp = x; /* Prevent optimization by compiler. */
return tmp != x;
}
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wolf99 commented Feb 2, 2017

NaN is the only "number" that is not equal to any other number, including itself. A simple test like return (x != x); would be optimised out by most compilers, thus the need for the addition of a volatile variable. Compilers do not always implement this aspect of doubles, so testing of this function's operation is required.

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