Beta returns the value of the complete beta function B(a, b).

BetaInc returns the value of the regularized incomplete beta function Iₓ(a, b) = 1 / B(a, b) * ∫₀ˣ tᵃ⁻¹ (1-t)ᵇ⁻¹ dt.

Choose returns the binomial coefficient of n and k.

GammaInc returns the value of the incomplete gamma function (also known as the regularized gamma function): P(a, x) = 1 / Γ(a) * ∫₀ˣ exp(-t) t**(a-1) dt.

GammaIncComp returns the complement of the incomplete gamma function 1 - GammaInc(a, x).

Lchoose returns math.Log(Choose(n, k)).

Sign returns the sign of x: -1 if x < 0, 0 if x == 0, 1 if x > 0.