AnthonyMikh/polygon_area.hs

## polygon_area.hs
import Control.Arrow ((***), (&&&))

shift = go
    where
        go [] = []
        go (x:xs) = xs ++ [x]

shiftedZipWith f = uncurry (zipWith f) . (&&&) id shift
shiftedSum = shiftedZipWith (+)
shiftedFSub = shiftedZipWith (flip (-))

polygonArea = curry $ (/2) . abs . sum . uncurry (zipWith (*)) . (***) shiftedSum shiftedFSub

main = print $ polygonArea [0, 0, 2] [0, 2, 0]
	import Control.Arrow ((***), (&&&))

	shift = go
	where
	go [] = []
	go (x:xs) = xs ++ [x]

	shiftedZipWith f = uncurry (zipWith f) . (&&&) id shift
	shiftedSum = shiftedZipWith (+)
	shiftedFSub = shiftedZipWith (flip (-))

	polygonArea = curry $ (/2) . abs . sum . uncurry (zipWith ()) . (**) shiftedSum shiftedFSub

	main = print $ polygonArea [0, 0, 2] [0, 2, 0]