c/numeric/math/isnan

Determines if the given floating point number is a not-a-number (NaN) value. The macro returns an integral value.

flt_eval_method is ignored: even if the argument is evaluated with more range and precision than its type, it is first converted to its semantic type, and the classification is based on that (this matters if the evaluation type supports NaNs, while the semantic type does not).

Return value
Nonzero integral value if is a NaN,  otherwise.