! Copyright (C) 2013 Dondy.
! See http://factorcode.org/license.txt for BSD license.
USING: kernel math math.functions locals vectors sequences prettyprint ;
IN: foobar

:: zig ( p1 p2 -- p3 )
    p1 first2 :> ( x1 y1 )
    p2 first2 :> ( x2 y2 )
    V{ } clone
    x1 x2 + y1 y2 - + 2 / suffix
    x2 x1 - y1 y2 + + 2 / suffix ;

:: zag ( p1 p2 -- p3 )
    p1 first2 :> ( x1 y1 )
    p2 first2 :> ( x2 y2 )
    V{ } clone
    x1 x2 + y1 y2 + - 2 / suffix
    x1 x2 - y1 y2 + + 2 / suffix ;

:: dragon ( p1 p2 p3 n seq -- seq )
    n 0 = [
        V{ } clone
        p1 suffix
        p2 suffix
        push-all
    ] [
        V{ } clone
        p1 p1 p2 zig p2 n 1 - dragon suffix
        p2 p2 p3 zag p3 n 1 - dragon suffix
        push-all
    ] if ;

: foobar ( -- )
    V{ } clone
    [let
        V{ 100 100 } :> p1
        V{ 356 100 } :> p2
        p1 p1 p2 zig p2 15 dragon ]
    . ;

MAIN: foobar