99b1bc43 ​

let g1: OList OList Bool
let g2: OList OList Bool

let input = flat [map (map (λb. if b blue black)) g1, [fill 4 yellow], map (map (λb. if b red black)) g2]

let output = zip (zip (λa. λb. if (a == b) black green)) g1 g2