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Fix layouts
author Yasutaka Higa <e115763@ie.u-ryukyu.ac.jp>
date Mon, 16 Feb 2015 15:05:11 +0900
parents ba7f0b5454ab
children
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headDelta :: Delta a -> a
headDelta (Mono  x)   = x
headDelta (Delta x _) = x

tailDelta :: Delta a -> Delta a
tailDelta (Mono x)     = Mono x
tailDelta (Delta _ ds) = ds


instance Monad Delta where
  return x = Mono x
  (Mono x) >>= f     = f x
  (Delta x d) >>= f  = Delta (headDelta (f x))
                             (d >>= (tailDelta . f))