[jarrett]

> with records of closures.

Interesting. Can you point me to an example?

[Jtsummers]

http://c2.com/cgi/wiki?ClosuresAndObjectsAreEquivalent

http://okmij.org/ftp/Scheme/oop-in-fp.txt

http://stackoverflow.com/questions/2954642/methods-and-prope...

http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-20.html

Some examples. The first is a discussion on it. The second and third have examples in scheme. I'd type more but I'm on my iPad. If I get time later I'll steal time on someone's computer to type up more.

[dllthomas]

Jtsummers gave some links, but in the interest of having something here:

    data Surface = Surface -- presumably provided by drawing backend
    data Shape = Shape
        { shapeGetCenter :: (Int, Int)
        , shapeSetCenter :: Int -> Int -> Shape
        , shapeDraw :: Surface -> IO ()
        , shapeScale :: Double -> Shape
        , shapeGetAABB :: (Int, Int, Int, Int)
        , shapeShow :: String
        }

    instance Show Shape where
        show = shapeShow

    circle r x y = Shape
        { shapeGetCenter = (x, y)
        , shapeSetCenter = circle r
        , shapeDraw = undefined -- draw shape to surface
        , shapeScale = \ f -> circle (f * r) x y
        , shapeGetAABB =
            ( floor $ fromIntegral x - r/2
            , floor $ fromIntegral y - r/2
            , ceiling $ fromIntegral x + r/2
            , ceiling $ fromIntegral y + r/2
            )
        , shapeShow = unwords [ "circle", show r, show x, show y ]
        }

    box w h theta x y = Shape
        { shapeGetCenter = (x, y)
        , shapeSetCenter = box w h theta
        , shapeDraw = undefined -- draw shape to surface
        , shapeScale = \ f -> box (w * f) (h * f) theta x y
        , shapeGetAABB =
            let w' = h * abs (sin theta)
                    + w * abs (cos theta)
                h' = w * abs (sin theta)
                    + h * abs (cos theta)
             in ( floor $ fromIntegral x - w'/2
                , floor $ fromIntegral y - h'/2
                , ceiling $ fromIntegral x + w'/2
                , ceiling $ fromIntegral y + h'/2
                )
        , shapeShow = unwords [ "box", show w, show theta, show x, show y ]
        }