Safe Haskell  SafeInfered 

Documentation
module Control.Arrow.Writer.Class
newtype WriterT w r a b Source
WriterT  

(Monoid w, Arrow r) => ArrowWriter w (WriterT w r)  
Monoid w => ArrowTransformer (WriterT w)  
(Monoid w, Arrow r) => Arrow (WriterT w r)  
(Monoid w, ArrowZero r) => ArrowZero (WriterT w r)  
(Monoid w, ArrowPlus r) => ArrowPlus (WriterT w r)  
(Monoid w, ArrowChoice r) => ArrowChoice (WriterT w r)  
(Monoid w, ArrowApply r) => ArrowApply (WriterT w r)  
(Monoid w, ArrowLoop r) => ArrowLoop (WriterT w r)  
(Monoid w, Arrow r) => Category (WriterT w r) 