SIMPLE SOLUTIONS

# FREXP(3) - Linux man page online | Library functions

Convert floating-point number to fractional and integral components.

Chapter
2017-09-15
FREXP(3) Linux Programmer's Manual FREXP(3)

## NAME

frexp, frexpf, frexpl - convert floating-point number to fractional and integral compo‐ nents

## SYNOPSIS

#include <math.h> double frexp(double x, int *exp); float frexpf(float x, int *exp); long double frexpl(long double x, int *exp); Link with -lm. 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 nor‐ malized 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[1], 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); }