Man page - expm1f(3)

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Manual

expm1

NAME
LIBRARY
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
ATTRIBUTES
STANDARDS
HISTORY
BUGS
SEE ALSO

NAME

expm1, expm1f, expm1l - exponential minus 1

LIBRARY

Math library ( libm , -lm )

SYNOPSIS

#include <math.h>

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

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

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.

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.

ERRORS

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.

ATTRIBUTES

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

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STANDARDS

C11, POSIX.1-2008.

HISTORY

C99, POSIX.1-2001. BSD.

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

SEE ALSO

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