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   expm1l    ( 3 )

экспоненциальный минус 1 (exponential minus 1)

Имя (Name)

expm1, expm1f, expm1l - exponential minus 1

Синопсис (Synopsis)

#include <math.h>

double expm1(double x); float expm1f(float x); long double expm1l(long double x);

Link with -lm.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

expm1(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 500 || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

expm1f(), expm1l(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE


Описание (Description)

These functions return a value equivalent to

exp(x) - 1

The result is computed in a way that is accurate even if the value of x is near zero—a case where exp(x) - 1 would be inaccurate due to subtraction of two numbers that are nearly equal.


Возвращаемое значение (Return value)

On success, these functions return exp(x) - 1.

If x is a NaN, a NaN is returned.

If x is +0 (-0), +0 (-0) is returned.

If x is positive infinity, positive infinity is returned.

If x is negative infinity, -1 is returned.

If the result overflows, a range error occurs, and the functions return -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL, respectively.


Ошибки (Error)

See math_error(7) for information on how to determine whether an
       error has occurred when calling these functions.

The following errors can occur:

Range error, overflow errno is set to ERANGE (but see BUGS). An overflow floating-point exception (FE_OVERFLOW) is raised.


Атрибуты (Attributes)

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

┌──────────────────────────────────────┬───────────────┬─────────┐ │Interface Attribute Value │ ├──────────────────────────────────────┼───────────────┼─────────┤ │expm1(), expm1f(), expm1l() │ Thread safety │ MT-Safe │ └──────────────────────────────────────┴───────────────┴─────────┘


Стандарты (Conforming to)

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

Ошибки (баги) (Bugs)

Before glibc 2.17, on certain architectures (e.g., x86, but not
       x86_64) expm1() raised a bogus underflow floating-point exception
       for some large negative x values (where the function result
       approaches -1).

Before approximately glibc version 2.11, expm1() raised a bogus invalid floating-point exception in addition to the expected overflow exception, and returned a NaN instead of positive infinity, for some large positive x values.

Before version 2.11, the glibc implementation did not set errno to ERANGE when a range error occurred.


Смотри также (See also)

exp(3), log(3), log1p(3)