C/math.h/signbit

int signbit(fpval): Returns nonzero if fpval is negative (that is, its sign bit is set)

<source lang="cpp">

1. include <stdio.h>
2. include <math.h>

int main(void) {

 printf("signbit(-1.0) %d\n", signbit(-1.0));
 printf("signbit(1.0) %d\n", signbit(1.0));
 printf("signbit(0.0) %d\n", signbit(0.0));
 return 0;

}

/* signbit(-1.0) 512 signbit(1.0) 0 signbit(0.0) 0

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