6.11.123 logbl Function

Calculates the signed exponent of a long double-precision floating-point value.

Include

<math.h>

Prototype

long double logbl(long double x);

Argument

x

any positive value for which to return the exponent

Return Value

Returns the exponent of x as a signed floating-point value. If x is 0, $\infty$ is returned.

Remarks

The argument is treated as being normalized if it is a subnormal floating-point value.

Example

See the notes at the beginning of this chapter or section for information on using printf() or scanf() (and other functions reading and writing the stdin or stdout streams) in the example code.

#include <math.h>
#include <stdio.h>
#include <errno.h>

int main(void)
{
  long double x, y;

  errno = 0;
  x = 13.45;
  y = logbl(x);
  if (errno)
    perror("Error");
  printf("The exponent of %Lf is %Lf\n", x, y);

  errno = 0;
  x = 0.0;
  y = logbl(x);
  if (errno)
    perror("Error");
  printf("The exponent of %Lf is %Lf\n", x, y);

  errno = 0;
  x = -2.0;
  y = logbl(x);
  if (errno)
    perror("Error");
  printf("The exponent of %Lf is %Lf\n", x, y);
}

Example Output

The exponent of 13.450000 is 3.000000
The exponent of 0.000000 is -inf
The exponent of -2.000000 is 1.000000