context Board :: set(row : int, col : int, value : int) : int
let square : Square = self.getSquare(row, col) in:
post:
        if not (row>=1 and row<=6 and col>=1 and col<=6 and value>=0 and value<=6 and not
isRepeated(row, col, value))
        then
                result= -1
                square.value = square.value@pre
        else if self.areas->exists(a : Area | not r.isComplete()) then
                result = 0
                square.value = value
        else
                result = 2
                square.value = value
        endif
endif