Commit 205f06a

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added: MonadWriter class

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Original file line number	Diff line number	Diff line change
`@@ -3,11 +3,13 @@ module WriterT where`
`3`	`3`
`4`	`4`	`import Control.Monad`
`5`	`5`	`import Control.Monad.Trans`
`6`		`-import Control.Monad.Writer`
`7`	`6`	`import Data.Monoid`
`8`	`7`
`9`	`8`	`newtype MyWriterT w m a = MyWriterT { runMyWriterT :: m (a,w) }`
`10`	`9`
	`10`	`+class Monad m => (MonadWriter w m) where`
	`11`	`+ tell :: (Monoid w, Monad m) => w -> MyWriterT w m ()`
	`12`	`+`
`11`	`13`	`instance (Monoid w, Monad m) => Functor (MyWriterT w m) where`
`12`	`14`	`fmap = liftM`
`13`	`15`

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