log-factorial ( n -- value )

Vocabulary

picomath

Inputs

n

an object

Outputs

value

an object

Definition

USING: combinators kernel locals.backend math math.constants
math.functions picomath.private sequences ;

IN: picomath

: log-factorial ( n -- value )
    {
        { [ dup 0 < ] [ "invalid input" throw ] }
        {
            [ dup 254 > ]
            [
                1 + [
                    load-local 0 get-local 0.5 -
                    0 get-local log * 0 get-local - 0.5 2 pi *
                    log * + 1.0 12.0 0 get-local * / +
                    1 drop-locals
                ] call
            ]
        }
        [ lf nth ]
    } cond ;