GNU/Linux man pages
Livre :
Expressions régulières,
Syntaxe et mise en oeuvre :
GNU/Linux |
CentOS 5.1 |
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tgammal(3) |
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tgamma, tgammaf, tgammal − true gamma function
#include <math.h>
double
tgamma(double x);
float tgammaf(float x);
long double tgammal(long double x);
Compile with −std=c99; link with −lm.
The Gamma function is defined by
Gamma(x) = integral from 0 to infinity of t^(x−1) e^−t dt
It is defined for every real number except for non-positive integers. For nonnegative integral m one has
Gamma(m+1) = m!
and, more generally, for all x:
Gamma(x+1) = x * Gamma(x)
Furthermore, the following is valid for all values of x outside the poles:
Gamma(x) * Gamma(1−x) = PI/sin(PI*x)
This function returns the value of the Gamma function for the argument x. It had to be called "true gamma function" since there is already a function gamma() that returns something else.
In order to check for errors, 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.
A range error occurs if x is too large. A pole error occurs if x is zero. A domain error (or a pole error) occurs if x is a negative integer.
C99.
gamma(3), lgamma(3)
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tgammal(3) | |