C库宏 ERANGE

#include <stdio.h>

#include <errno.h>

#include <math.h>



int main () {

   double x;

   double value;



   x = 2.000000;

   value = log(x);



   if( errno == ERANGE ) {

      printf("Log(%f) is out of range\n", x);

   } else {

      printf("Log(%f) = %f\n", x, value);

   }



   x = 1.000000;

   value = log(x);



   if( errno == ERANGE ) {

      printf("Log(%f) is out of range\n", x);

   } else {

      printf("Log(%f) = %f\n", x, value);

   }



   x = 0.000000;

   value = log(x);



   if( errno == ERANGE ) {

      printf("Log(%f) is out of range\n", x);

   } else {

      printf("Log(%f) = %f\n", x, value);

   }



   return 0;

}