1 #include <math.h> 2 3 double fmax(double x, double y) 4 { 5 if (isnan(x)) 6 return y; 7 if (isnan(y)) 8 return x; 9 /* handle signed zeros, see C99 Annex F.9.9.2 */ 10 if (signbit(x) != signbit(y)) 11 return signbit(x) ? y : x; 12 return x < y ? y : x; 13 } 14