FREXP(3) Linux Programmer's Manual FREXP(3)

# NAME

frexp, frexpf, frexpl - convert floating-point number to fractional and integral components

# SYNOPSIS

```#include <math.h>
```
```double frexp(double x, int *exp);
float frexpf(float x, int *exp);
long double frexpl(long double x, int *exp);
```

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
frexpf(), frexpl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

# DESCRIPTION

These functions are used to split the number x into a normalized fraction and an exponent which is stored in exp.

# RETURN VALUE

These functions return the normalized fraction. If the argument x is not zero, the normalized fraction is x times a power of two, and its absolute value is always in the range 1/2 (inclusive) to 1 (exclusive), that is, [0.5,1).
If x is zero, then the normalized fraction is zero and zero is stored in exp.
If x is a NaN, a NaN is returned, and the value of *exp is unspecified.
If x is positive infinity (negative infinity), positive infinity (negative infinity) is returned, and the value of *exp is unspecified.

No errors occur.

# ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).
 Interface Attribute Value frexp (), frexpf (), frexpl () Thread safety MT-Safe

# CONFORMING TO

C99, POSIX.1-2001, POSIX.1-2008.
The variant returning double also conforms to SVr4, 4.3BSD, C89.

# EXAMPLE

The program below produces results such as the following:

```\$ ./a.out 2560
frexp(2560, &e) = 0.625: 0.625 * 2^12 = 2560
\$ ./a.out -4
frexp(-4, &e) = -0.5: -0.5 * 2^3 = -4
```

## Program source

```#include <math.h>
#include <float.h>
#include <stdio.h>
#include <stdlib.h>

int
main(int argc, char *argv[])
{
double x, r;
int exp;

x = strtod(argv, NULL);
r = frexp(x, &exp);

printf("frexp(%g, &e) = %g: %g * %d^%d = %g\n",
x, r, r, FLT_RADIX, exp, x);
exit(EXIT_SUCCESS);
}
```