[Haskell-beginners] Pipe and typeclasses

[Karol Samborski]

2013/7/23 Emmanuel Surleau <emmanuel.surleau at gmail.com>

> Hello,
>
> I have seen from time to time the pipe symbol in type signatures, like so:
>
>   class Monad m => MonadReader r m | m -> r where
>
> How should I interpret that ? Or more to the point, how does the compiler
> interpret it?
>

Hi Emmanuel!

The pipe symbol is for a functional dependency:
http://www.haskell.org/haskellwiki/Functional_dependencies

Karol
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