ref: 5a6ed7f45e6d79d0a555c26ac87b0c0c2f0bfc6d dir: /isnanf.c/
#include <u.h> int isnanf(float f) { union { float f; u32int u; }x; x.f = f; return (x.u & (0xff<<23)) == (0xff<<23); }