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   frexp    ( 3 )

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Имя (Name)

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

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Синопсис (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 <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

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Описание (Description)

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

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Возвращаемое значение (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.

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Ошибки (Error)

No errors occur.

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Атрибуты (Attributes)

For an explanation of the terms used in this section, see attributes(7).

┌──────────────────────────────────────┬───────────────┬─────────┐ │Interface │ Attribute │ Value │ ├──────────────────────────────────────┼───────────────┼─────────┤ │frexp(), frexpf(), frexpl() │ Thread safety │ MT-Safe │ └──────────────────────────────────────┴───────────────┴─────────┘

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Стандарты (Conforming to)

C99, POSIX.1-2001, POSIX.1-2008.

The variant returning double also conforms to SVr4, 4.3BSD, C89.

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Примеры (Examples)

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);
       }

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Смотри также (See also)

ldexp(3), modf(3)

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