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Object Oriented Programming

type Point = {x: Int, y: Int}

value moveX₀ =
   fun(p: Point, dx: Int) p.x := p.x + dx; p
value moveX =
   all[P <= Point] fun(p:P, dx: Int) p.x := p.x + dx; p

type Tile = {x: Int, y: Int, hor: Int, ver: Int}
moveX[Tile]({x = 0, y = 0, hor - 1, ver = 1}, 1).hor

• Result of moveX is same as argument type.
• moveX can be applied to objects of (yet) unknown type.