std::lgamma

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Defined in header <cmath>
float       lgamma( float arg );		(C++11 feature)
double      lgamma( double arg );		(C++11 feature)
long double lgamma( long double arg );		(C++11 feature)

Computes the natural logarithm of the absolute value of the gamma function of arg.

Contents 1 Parameters 2 Return value 3 Exceptions 4 Notes 5 See also 6 External links

[edit] Parameters

arg

-

floating point value

[edit] Return value

The value of the logarithm of the gamma function of arg, that is log
e|∫∞
0targ-1
e^-t dt|.

If arg is a natural number, std::lgamma(arg) is the logarithm of the factorial of arg-1.

[edit] Exceptions

If arg is zero or a negative integer, pole error may occur and FE_INVALID or FE_DIVBYZERO may be raised.

If arg is too large, range error may occur and FE_OVERFLOW may be raised.

[edit] Notes

POSIX specification additionally requires that each execution of lgamma stores the sign of the gamma function of arg in the external variable signgam.

[edit] See also

tgamma (C++11)	gamma function (function)

[edit] External links

Weisstein, Eric W. "Log Gamma Function." From MathWorld--A Wolfram Web Resource.