floating point - NaN Literal in C?

Question

How do you write an NaN floating-point literal in C?

Answer 1

In C99's <math.h>

  7.12  Mathematics <math.h>

   [#5] The macro

           NAN

   is defined if and only if the implementation supports  quiet
   NaNs   for  the  float  type.   It  expands  to  a  constant
   expression of type float representing a quiet NaN.           |