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Description
An example of the composite pattern implemented simply with functions and object expressions
Source code
type Point = Point of int * int type DrawingInstruction = Line of Point * Point type Shape = abstract Draw: unit -> DrawingInstruction list abstract HitTest: Point -> bool let line (p1:Point) (p2:Point) = { new Shape with member this.Draw() = [Line(p1, p2)] member this.HitTest(point) = true } let compositeShape (shapes:Shape list) = { new Shape with member this.Draw() = [ for shape in shapes do for instr in shape.Draw() do yield instr ] member this.HitTest(point) = shapes |> List.exists(fun shape -> shape.HitTest(point)) }
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patterns
patterns
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