[Haskell-cafe] Adding state to a library

[Kevin Jardine]

My apologies. My last message was sent prematurely.

I have a library of functions that all take a config parameter (and usually
others) and return results in the IO monad.

It is sometimes useful to drop the config parameter by using a state-like
monad..

I have found that I can wrap all my functions like so:

withLibrary cfg f = f cfg

stateF a b c d =
   getConfig >>= \cfg -> liftIO $ withLibrary cfg
   libraryF a b c d

notice that I need stateF and libraryF lines, each with n parameters.

Upgrading my library like this is rather tedious.

I would prefer to just write something like

stateF = upgrade libraryF

but I can find no way to define the function upgrade in Haskell.

This must be a fairly common problem. Is there a simple solution?

On Sun, Dec 18, 2011 at 10:20 PM, Kevin Jardine <kevinjardine at gmail.com>wrote:

> I have a library of functions that all take cfg parameter (and usually
> others) and return results in the IO monad.
>
> It is sometimes useful to drop the config parameter by using a state-like
> monad..
>
> I have found that I can wrap all my functions like so:
>
> withLibrary cfg f = f cfg
>
> stateF a b c d =
>
>
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