FREXP(3) Linux Programmer's Manual FREXP(3)NAME
frexp, frexpf, frexpl - convert floating-point number to fractional and
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(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600
|| _ISOC99_SOURCE; or cc -std=c99
The frexp() function is used to split the number x into a normalized
fraction and an exponent which is stored in exp.
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 (exclu‐
sive), that is, [0.5,1).
If x is zero, then the normalized fraction is zero and zero is stored
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 (nega‐
tive infinity) is returned, and the value of *exp is unspecified.
No errors occur.
C99, POSIX.1-2001. The variant returning double also conforms to SVr4,
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
main(int argc, char *argv)
double x, r;
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);
} /* main */
SEE ALSOldexp(3), modf(3)COLOPHON
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