Mercurial > hg > Papers > 2015 > atton-thesis

view prepaper/src/delta_instance_monad.hs @ 63:c75ba6313e39

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Writing prepaper...
author Yasutaka Higa <e115763@ie.u-ryukyu.ac.jp>
date Tue, 17 Feb 2015 12:08:10 +0900
parents
children
line wrap: on
line source

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))