Question

How to use signbit() function to determine if a given floating point number is negative in C

Answer 1

#include <stdio.h>     
#include <math.h>
 
int main(int argc, char **argv)
{   
	printf("signbit(+0.0) = %d\n", signbit(+0.0));
    printf("signbit(-0.0) = %d\n", signbit(-0.0));
	printf("signbit(1.0 / 0.0) = %d\n", signbit(1.0 / 0.0));
	printf("signbit(-1.0 / 0.0) = %d\n", signbit(-1.0 / 0.0));
  
    return 0;
}

// Return value: non-zero (true) if the sign of N is negative, ​0​ otherwise
 
/*
run:
   
signbit(+0.0) = 0
signbit(-0.0) = 1
signbit(1.0 / 0.0) = 0
signbit(-1.0 / 0.0) = 1

*/

 

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