( --- Complex integer arithmetic --- )

: c* ( x1 y1 x2 y2 -- x3 y3 )
        swap -rot               ( x1 x2 y1 y2 )
        2dup * negate           ( x1 x2 y1 y2 -y1y2 )
        4 pick 4 pick * +       ( x1 x2 y1 y2 (x1x2-y1y2))
        4 roll 2 roll *         ( x2 y1 (x1x2-y1y2) x1y2 )
        3 roll 3 roll * +       ( (x1x2-y1y2) (x1y2+x2y1) )
;

: c+ ( x1 y1 x2 y2 -- x3 y3 )
        rot +
        -rot +
        swap
;

: csq 2dup c* ;

: cmagsq ( x1 y1 -- mag )
        csq abs
;

( --- Mandelbrot set calculations  --- )

: iterate ( cr ci zr zi -- cr ci z'r z'i )
        csq c+
;

: inSet? ( cr ci -- res )
    
    100 0 DO

        2SWAP 2DUP 5 ROLL 5 ROLL
        iterate
        2DUP cmagsq
        100 > IF
            LEAVE
        THEN

    LOOP
;