phi ( x -- value )

Vocabulary

picomath

Inputs

x

an object

Outputs

value

an object

Definition

USING: kernel math math.functions picomath.private ;

IN: picomath

:: phi ( x -- value )
    x 0 >= 1 -1 ? :> sign x abs 2 sqrt / :> x! p x * 1 +
    recip :> t a5 t * a4 + t * a3 + t * a2 + t * a1 + t *
    x x neg * e^ * 1 swap - :> y sign y * 1 + 2 / ;