Re: [Haskelldb-users] What about introducing a Connection type declaration?

[Bjorn B. <bri...@cs...>]

On Aug 6, 2006, at 5:15 PM, Marc Weber wrote:

> eg mysqlConnect is of type:
> mysqlConnect :: MonadIO m =3D> MySQLOptions -> (Database -> m a) -> m =
a
>
> Typical usage looks like this, doesn't it?
>
>
> 	doSomething :: MonadIO m =3D> (Database -> m a) -> m a -> IO () =
-- <<
> 	main=3Ddo
> 		con <- mysqlConnect Options
> 		doSomething con ..
>
> Wouln't it be mucht clearer to use another typedef to write =20
> something like this ?
>
>
> 	newtype CConnection :: MonadIO m =3D> (Database -> m a) -> m a
> 	doSomething :: CConnection -> IO ()  -- <<  much shorter and =
clearer
> 	main=3Ddo
> 		con <- mysqlConnect Options
> 		doSomething con ..
>
> The first C migt indicate that it's a "connected" connection =20
> (parameters have already been applied)..
> Or does this already exist?
>
> I'd like to provide a patch if you consider it useful
>
> Greetings
> Marc Weber

Hi Marc,

I'm not sure that I completely understand your example. I think that =20
there is something wrong with the types.

Here's how I think a typical application looks with the current types:

options :: MysqlOptions
options =3D ...

doSomething :: Database -> IO ()
doSomething db =3D ...

main :: IO ()
main =3D mysqlConnect options doSomething


I probably misunderstood what you want to do though.

/Bj=F6rn