char
_lngamma(
floatnum x,
int digits)
{
floatstruct factor;
int infinity;
char result;
if (float_cmp(x, &c1) == 0 || float_cmp(x, &c2) == 0)
return _setzero(x);
float_create(&factor);
result = _lngamma_prim(x, &factor, &infinity, digits)
&& infinity == 0;
if (result)
{
float_abs(&factor);
_ln(&factor, digits + 1);
result = float_sub(x, x, &factor, digits+1);
}
float_free(&factor);
if (infinity != 0)
return _seterror(x, ZeroDivide);
if (!result)
float_setnan(x);
return result;
}
char
float_raisei(
floatnum power,
cfloatnum base,
int exponent,
int digits)
{
if (digits <= 0 || digits > maxdigits)
return _seterror(power, InvalidPrecision);
if (float_isnan(base))
return _seterror(power, NoOperand);
if (float_iszero(base))
{
if (exponent == 0)
return _seterror(power, OutOfDomain);
if (exponent < 0)
return _seterror(power, ZeroDivide);
return _setzero(power);
}
digits += 14;
if (digits > maxdigits)
digits = maxdigits;
float_copy(power, base, digits);
if (!_raisei(power, exponent, digits)
|| !float_isvalidexp(float_getexponent(power)))
{
if (float_getexponent(base) < 0)
return _seterror(power, Underflow);
return _seterror(power, Overflow);
}
return 1;
}
char
float_raise(
floatnum power,
cfloatnum base,
cfloatnum exponent,
int digits)
{
signed char sgn;
if (float_isnan(exponent) || float_isnan(base))
return _seterror(power, NoOperand);
if (digits <= 0 || digits > MATHPRECISION)
return _seterror(power, InvalidPrecision);
if (float_iszero(base))
{
switch(float_getsign(exponent))
{
case 0:
return _seterror(power, OutOfDomain);
case -1:
return _seterror(power, ZeroDivide);
}
return _setzero(power);
}
sgn = float_getsign(base);
if (sgn < 0)
{
if (!float_isinteger(exponent))
return _seterror(power, OutOfDomain);
if ((float_getdigit(exponent, float_getexponent(exponent)) & 1) == 0)
sgn = 1;
}
float_copy(power, base, digits+1);
float_abs(power);
if (!_raise(power, exponent, digits))
{
float_seterror(Overflow);
if (float_getexponent(base) * float_getsign(exponent) < 0)
float_seterror(Underflow);
return _setnan(power);
}
float_setsign(power, sgn);
return 1;
}
static char
_pochhammer_i(
floatnum x,
cfloatnum n,
int digits)
{
/* do not use the expensive Gamma function when a few
multiplications do the same */
/* pre: n is an integer */
int ni;
signed char result;
if (float_iszero(n))
return float_copy(x, &c1, EXACT);
if (float_isinteger(x))
{
result = -1;
float_neg((floatnum)n);
if (float_getsign(x) <= 0 && float_cmp(x, n) > 0)
/* x and x+n have opposite signs, meaning 0 is
among the factors */
result = _setzero(x);
else if (float_getsign(x) > 0 && float_cmp(x, n) <= 0)
/* x and x+n have opposite signs, meaning at one point
you have to divide by 0 */
result = _seterror(x, ZeroDivide);
float_neg((floatnum)n);
if (result >= 0)
return result;
}
if (float_getexponent(x) < EXPMAX/100)
{
ni = float_asinteger(n);
if (ni != 0 && ni < 50 && ni > -50)
return _pochhammer_si(x, ni, digits+2);
}
return _pochhammer_g(x, n, digits);
}