экспоненциальная функция (exponential function)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
exp, expf, expl — exponential function
Синопсис (Synopsis)
#include <math.h>
double exp(double x);
float expf(float x);
long double expl(long double x);
Описание (Description)
The functionality described on this reference page is aligned
with the ISO C standard. Any conflict between the requirements
described here and the ISO C standard is unintentional. This
volume of POSIX.1‐2017 defers to the ISO C standard.
These functions shall compute the base-e exponential of x.
An application wishing to check for error situations should set
errno to zero and call feclearexcept(FE_ALL_EXCEPT) before
calling these functions. On return, if errno is non-zero or
fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW |
FE_UNDERFLOW) is non-zero, an error has occurred.
Возвращаемое значение (Return value)
Upon successful completion, these functions shall return the
exponential value of x.
If the correct value would cause overflow, a range error shall
occur and exp(), expf(), and expl() shall return the value of the
macro HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.
If the correct value would cause underflow, and is not
representable, a range error may occur, and exp(), expf(), and
expl() shall return 0.0, or (if the IEC 60559 Floating-Point
option is not supported) an implementation-defined value no
greater in magnitude than DBL_MIN, FLT_MIN, and LDBL_MIN,
respectively.
If x is NaN, a NaN shall be returned.
If x is ±0, 1 shall be returned.
If x is -Inf, +0 shall be returned.
If x is +Inf, x shall be returned.
If the correct value would cause underflow, and is representable,
a range error may occur and the correct value shall be returned.
Ошибки (Error)
These functions shall fail if:
Range Error The result overflows.
If the integer expression (math_errhandling &
MATH_ERRNO) is non-zero, then errno shall be set to
[ERANGE]. If the integer expression
(math_errhandling & MATH_ERREXCEPT) is non-zero, then
the overflow floating-point exception shall be
raised.
These functions may fail if:
Range Error The result underflows.
If the integer expression (math_errhandling &
MATH_ERRNO) is non-zero, then errno shall be set to
[ERANGE]. If the integer expression
(math_errhandling & MATH_ERREXCEPT) is non-zero, then
the underflow floating-point exception shall be
raised.
The following sections are informative.
Примеры (Examples)
Computing the Density of the Standard Normal Distribution
This function shows an implementation for the density of the
standard normal distribution using exp(). This example uses the
constant M_PI which is part of the XSI option.
#include <math.h>
double
normal_density (double x)
{
return exp(-x*x/2) / sqrt (2*M_PI);
}
Использование в приложениях (Application usage)
On error, the expressions (math_errhandling & MATH_ERRNO) and
(math_errhandling & MATH_ERREXCEPT) are independent of each
other, but at least one of them must be non-zero.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
feclearexcept(3p), fetestexcept(3p), isnan(3p), log(3p)
The Base Definitions volume of POSIX.1‐2017, Section 4.20,
Treatment of Error Conditions for Mathematical Functions,
math.h(0p)
