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():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;

or cc -std=c99

# DESCRIPTION¶

The frexp() function is used to split the number x into a normalized fraction and an exponent which is stored in exp.

# RETURN VALUE¶

The frexp() function returns 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¶

The frexp(), frexpf(), and frexpl() functions are thread-safe.

# CONFORMING TO¶

C99, POSIX.1-2001. 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);
}
```