Naming conventions for newtype deconstructors (destructors?)

Posted by Petr Pudlák on Programmers See other posts from Programmers or by Petr Pudlák
Published on 2012-10-12T11:51:27Z Indexed on 2012/10/12 15:48 UTC
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coding-standards

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haskell

Looking into Haskell's standard library we can see:

newtype StateT s m a = StateT { runStateT :: s -> m (a, s) }

newtype WrappedMonad m a = WrapMonad { unwrapMonad :: m a }

newtype Sum a = Sum { getSum :: a }

Apparently, there (at least) 3 different prefixes used to unwrap a value inside a newtype: un-, run- and get-. (Moreover run- and get- capitalizes the next letter while un- doesn't.) This seems confusing.

Are there any reasons for that, or is that just a historical thing?
If I design my own newtype, what prefix should I use and why?

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