Slide 13
Slide 13 text
Tic Tac Toe
placeMark : (freePos: List Pos) -> Pos-> List Pos
vs
placeMark : (freePos: Vect (S n) Pos) // available positions, (S n) means n+1
-> (p: Pos) // position to be marked
-> (Elem p freePos) // proof that position p is in freePos
-> Vect n Pos // remaining positions, 1 less than input