intersect-range ( range1 range2 -- range3 )

Vocabulary

ranges.private

Inputs

range1	an object
range2	an object

Outputs

range3

an object

Definition

USING: kernel math math.order ranges sequences ;

IN: ranges.private

:: intersect-range ( range1 range2 -- range3 )
    range1 empty? range2 empty? or
    [ empty-range ] [
        range1 >forward-range< :> ( start1 stop1 step1 ) range2
        >forward-range< :> ( start2 stop2 step2 ) step1 step2
        gcd :> ( x g ) start1 start2 -
        g /mod :> ( z y ) y zero? not
        [ empty-range ] [
            start1 x z step1 * * - :> b step1 step2 lcm
            :> a start1 start2 [ b over - a rem + ] bi@ max
            :> m stop1 stop2 [ dup b - a rem - ] bi@ min
            :> n m n a <range>
        ] if
    ] if ;