RosettaCodeData/Task/Gamma-function/Forth/gamma-function-1.fth

16 lines
453 B
Forth

8 constant (gamma-shift)
: (mortici) ( f1 -- f2)
-1 s>f f+ 1 s>f
fover 271828183e-8 f* 12 s>f f* f/
fover 271828183e-8 f/ f+
fover f** fswap
628318530e-8 f* fsqrt f* \ 2*pi
;
: gamma ( f1 -- f2)
fdup f0< >r fdup f0= r> or abort" Gamma less or equal to zero"
fdup (gamma-shift) s>f f+ (mortici) fswap
1 s>f (gamma-shift) 0 do fover i s>f f+ f* loop fswap fdrop f/
;