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mpfr_libmpfr_lgamma Method (mpfr_t, Int32, mpfr_t, mpfr_rnd_t)
Set rop to the value of the logarithm of the absolute value of the Gamma function on op rounded in the direction rnd.

Namespace:  Math.Mpfr.Native
Assembly:  Math.Mpfr.Native (in Math.Mpfr.Native.dll) Version: 1.0.0.0 (1.0.0.0)
Syntax
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public static int mpfr_lgamma(
	mpfr_t rop,
	ref int signp,
	mpfr_t op,
	mpfr_rnd_t rnd
)

Parameters

rop
Type: Math.Mpfr.Nativempfr_t
The result floating-point number.
signp
Type: SystemInt32
The returned sign.
op
Type: Math.Mpfr.Nativempfr_t
The operand floating-point number.
rnd
Type: Math.Mpfr.Nativempfr_rnd_t
The rounding direction.

Return Value

Type: Int32
Return zero, a positive, or a negative value if rop is respectively equal to, greater than, or lower than the exact result. See GNU MPFR - Rounding Modes for details.
Remarks

The sign (1 or -1) of Gamma(op) is returned in the object pointed to by signp. When op is 1 or 2, set rop to +0 (in all rounding modes). When op is an infinity or a nonpositive integer, set rop to +Inf. When op is NaN, -Inf or a negative integer, signp is undefined, and when op is ±0, signp is the sign of the zero.

Examples
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// Create, initialize, and set a new floating-point number op to 10.4.
mpfr_t op = new mpfr_t();
mpfr_lib.mpfr_init2(op, 64U);
Assert.IsTrue(mpfr_lib.mpfr_set_d(op, 10.4, mpfr_rnd_t.MPFR_RNDN) == 0);

// Create and initialize a new floating-point number rop.
mpfr_t rop = new mpfr_t();
mpfr_lib.mpfr_init2(rop, 64U);

// Set rop to log(|Gamma(op)|).
int sign = 0;
Assert.IsTrue(mpfr_lib.mpfr_lgamma(rop, ref sign, op, mpfr_rnd_t.MPFR_RNDN) == -1);

// Assert the value of rop and sign.
Assert.IsTrue(rop.ToString() == "0.137108263716202786516e2" && sign == 1);

// Release unmanaged memory allocated for rop and op.
mpfr_lib.mpfr_clears(rop, op, null);
See Also