Originální popis anglicky:
expm1, expm1f, expm1l - compute exponential functions
Návod, kniha: POSIX Programmer's Manual
#include <math.h>
double expm1(double
x);
float expm1f(float
x);
long double expm1l(long double
x);
These functions shall compute
e**x-1.0.
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.
Upon successful completion, these functions return
e**x-1.0.
If the correct value would cause overflow, a range error shall occur and
expm1(),
expm1f(), and
expm1l() shall return the value of
the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.
If
x is NaN, a NaN shall be returned.
If
x is ±0, ±0 shall be returned.
If
x is -Inf, -1 shall be returned.
If
x is +Inf,
x shall be returned.
If
x is subnormal, a range error may occur and
x should be
returned.
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 value of x is subnormal.
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.
None.
The value of
expm1(
x) may be more accurate than
exp(
x)-1.0 for small values of
x.
The
expm1() and
log1p() functions are useful for financial
calculations of ((1+
x)**
n-1)/
x, namely:
when
x is very small (for example, when calculating small daily interest
rates). These functions also simplify writing accurate inverse hyperbolic
functions.
For IEEE Std 754-1985
double, 709.8 <
x implies
expm1(
x) has overflowed.
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.
None.
None.
exp() ,
feclearexcept() ,
fetestexcept() ,
ilogb() ,
log1p() , the Base Definitions volume of
IEEE Std 1003.1-2001, Section 4.18, Treatment of Error
Conditions for Mathematical Functions,
<math.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
