log-gamma ( x -- value )


Vocabulary
picomath

Inputs and outputs
xan object
valuean object


Definition


:: log-gamma ( x -- value )
x 0 <= [ "Invalid input" throw ] when x 12 <
[ x gamma abs log ] [
1.0 x x * / :> z 7 c nth 7 <iota> reverse
[ [ z * ] [ c nth ] bi* + ] each x / :> series x 0.5 -
x log * x - halfLogTwoPi + series +
] if ;