Obtains the greater of two arguments.
double fmax(double d1, double d2);
float fmaxf(float d1, float d2);
long double fmaxl(long double d1, long double d2);
The fmax function group recognizes a not-a-number as a lack of data. When one argument is a not-a-number and the other is a numeric value, the function returns the numeric value.