# frexp(2) [plan9 man page]

```FREXP(2)							System Calls Manual							  FREXP(2)

NAME
frexp, ldexp, modf - split into mantissa and exponent

SYNOPSIS
#include <u.h>
#include <libc.h>

double frexp(double value, int *eptr)

double ldexp(double value, int exp)

double modf(double value, double *iptr)

DESCRIPTION
Frexp returns the mantissa of value and stores the exponent indirectly through eptr, so that value = frexp(value)*2**(*eptr).

Ldexp returns the quantity value*2**exp.

Modf returns the positive fractional part of value and stores the integer part indirectly through iptr.

SOURCE
/sys/src/libc/\$objtype/frexp.c

intro(2)

DIAGNOSTICS
Ldexp returns 0 for underflow and the appropriately signed infinity for overflow.

FREXP(2)```

## Check Out this Related Man Page

```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.

ERRORS
No errors occur.

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[1], NULL);
r = frexp(x, &exp);

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

ldexp(3), modf(3)

COLOPHON
This page is part of release 3.44 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
be found at http://www.kernel.org/doc/man-pages/.

2010-09-20								  FREXP(3)```
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