009d5c81 ​

type Mark =
  | A of [[black, blue, black], [blue, blue, blue], [black, blue, black]]
  | B of [[blue, black, blue], [black, blue, black], [blue, blue, blue]]
  | C of [[blue, blue, blue], [blue, black, blue], [black, blue, black]]

let g: Grid
let p: Loc
let s: Mark

let input =
  grid p s g

let output =
  gmap (λc. if (c == black) black (match s with
    | A -> red
    | B -> green
    | C -> orange
  )) g