xlgamma.cpp

C语言库函数的原型,有用的拿去

// xlgamma: moderately accurate lgamma function for TR1 random
#include <cmath>

 #if _HAS_TR1
//  #include <random>
_STD_BEGIN
	namespace tr1 {	// TR1 additions

_CRTIMP2_PURE float __CLRCALL_PURE_OR_CDECL _XLgamma(float);
_CRTIMP2_PURE double __CLRCALL_PURE_OR_CDECL _XLgamma(double);
_CRTIMP2_PURE long double __CLRCALL_PURE_OR_CDECL _XLgamma(long double);

float __CLRCALL_PURE_OR_CDECL _XLgamma(float x)
	{	// moderately accurate log gamma
	static float coeff[6] =
		{ 76.18009172947146F,
		  -86.50532032941677F,
		  24.01409824083091F,
		  -1.23173972450155F,
		  0.1208650973866179E-2F,
		  -0.5395239384953E-5F};

	float val0 = x + 5.5F;
	val0 -= (x + 0.5F) * _STD log(val0);
	float val1 = 1.000000000190015F;
	float y = x + 1.0F;

	for (int i = 0; i < 6; ++i, y += 1.0)
		val1 += coeff[i] / y;
	return (-val0 + _STD log(2.5066282746310005F * val1 / x));
	}

double __CLRCALL_PURE_OR_CDECL _XLgamma(double x)
	{	// moderately accurate log gamma
	static double coeff[6] =
		{ 76.18009172947146,
		  -86.50532032941677,
		  24.01409824083091,
		  -1.23173972450155,
		  0.1208650973866179E-2,
		  -0.5395239384953E-5};

	double val0 = x + 5.5;
	val0 -= (x + 0.5) * _STD log(val0);
	double val1 = 1.000000000190015;
	double y = x + 1;

	for (int i = 0; i < 6; ++i, y += 1.0)
		val1 += coeff[i] / y;
	return (-val0 + _STD log(2.5066282746310005 * val1 / x));
	}

long double __CLRCALL_PURE_OR_CDECL _XLgamma(long double x)
	{	// moderately accurate log gamma
	static long double coeff[6] =
		{ 76.18009172947146,
		  -86.50532032941677,
		  24.01409824083091,
		  -1.23173972450155,
		  0.1208650973866179E-2,
		  -0.5395239384953E-5};

	long double val0 = x + 5.5;
	val0 -= (x + 0.5) * _STD log(val0);
	long double val1 = 1.000000000190015;
	long double y = x + 1;

	for (int i = 0; i < 6; ++i, y += 1.0)
		val1 += coeff[i] / y;
	return (-val0 + _STD log(2.5066282746310005 * val1 / x));
	}

	}	// namespace tr1
_STD_END
 #endif /* _HAS_TR1 */

/*
 * Copyright (c) 1992-2008 by P.J. Plauger.  ALL RIGHTS RESERVED.
 * Consult your license regarding permissions and restrictions.
V5.05:0009 */