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view src/delta_instance_monad.hs @ 49:ba7f0b5454ab

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Add description for DeltaM definition
author Yasutaka Higa <e115763@ie.u-ryukyu.ac.jp>
date Sun, 15 Feb 2015 14:07:07 +0900
parents c4da3e667aad
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))