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gammap() double gammap ( double  a, double  x  ) Normalized incomplete gamma function P(a, x) Purpose gammap computes the normalized incomplete gamma function P(a, x). P(a, x) = γ(a, x)/Γ(a) = (1/Γ(a))∫ t^(a-1)*exp(-t) dt [0, x] Returns Normalized incomplete gamma function P(a, x). Parameters [in] a Argument a. (a > 0) [in] x Argument x. (x >= 0) Error handling If a <= 0 or x < 0, domain error (EDOM) occurs. Range error (ERANGE) may occur. Reference boost/math/special_functions