Originální popis anglicky:
tgamma, tgammaf, tgammal - compute gamma() function
Návod, kniha: POSIX Programmer's Manual
#include <math.h>
double tgamma(double
x);
float tgammaf(float
x);
long double tgammal(long double
x);
These functions shall compute the
gamma() function 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.
Upon successful completion, these functions shall return
Gamma(
x).
If
x is a negative integer, a domain error shall occur, and either a NaN
(if supported), or an implementation-defined value shall be returned.
If the correct value would cause overflow, a range error shall occur and
tgamma(),
tgammaf(), and
tgammal() shall return
±HUGE_VAL, ±HUGE_VALF, or ±HUGE_VALL, respectively, with
the same sign as the correct value of the function.
If
x is NaN, a NaN shall be returned.
If
x is +Inf,
x shall be returned.
If
x is ±0, a pole error shall occur, and
tgamma(),
tgammaf(), and
tgammal() shall return ±HUGE_VAL,
±HUGE_VALF, and ±HUGE_VALL, respectively.
If
x is -Inf, a domain error shall occur, and either a NaN (if
supported), or an implementation-defined value shall be returned.
These functions shall fail if:
- Domain Error
- The value of x is a negative integer, or
x is -Inf.
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then
errno shall be set to [EDOM]. If the integer expression
(math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid
floating-point exception shall be raised.
- Pole Error
- The value of x is zero.
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 divide-by-zero
floating-point exception shall be raised.
- Range Error
- The value 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.
The following sections are informative.
None.
For IEEE Std 754-1985
double, overflow happens when 0 <
x < 1/DBL_MAX, and 171.7 <
x.
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.
This function is named
tgamma() in order to avoid conflicts with the
historical
gamma() and
lgamma() functions.
It is possible that the error response for a negative integer argument may be
changed to a pole error and a return value of ±Inf.
feclearexcept() ,
fetestexcept() ,
lgamma() , 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
.
