the incomplete gamma function, denoted @samp{P(a,x)}. This is defined by
the integral,
@texline @math{P(a,x) = \left( \int_0^x t^{a-1} e^t dt \right) / \Gamma(a)}.
-@infoline @samp{gammaP(a,x) = integ(t@sup{a-1} exp@sup{t}, t, 0, x) / gamma(a)}.
+@infoline @samp{gammaP(a,x) = integ(t@sup{a-1} e@sup{t}, t, 0, x) / gamma(a)}.
This implies that @samp{gammaP(a,inf) = 1} for any @expr{a} (see the
definition of the normal gamma function).