Incomplete gamma integral and its complement
real gammaIncompleteCompl (
) pure nothrow @nogc @safe;
These functions are defined by
gammaIncomplete = ( ∫0x e-t ta-1 dt )/ Γ(a)
gammaIncompleteCompl(a,x) = 1 - gammaIncomplete(a,x) = (∫x∞ e-t ta-1 dt )/ Γ(a)
In this implementation both arguments must be positive. The integral is evaluated by either a power series or continued fraction expansion, depending on the relative values of a and x.
Stephen L. Moshier (original C code). Conversion to D by Don Clugston