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List:       haskell
Subject:    RE: Singletons and Reflection
From:       "Daan Leijen" <daan () cs ! uu ! nl>
Date:       1999-12-15 12:48:49
Message-ID: 000401bf46fa$6699ff80$9650d383 () cs ! uu ! nl
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> If we had implicit parameters then all graphics functions 
> would have types
> (? context :: Context) => (explicit arguments) => IO (result) 
> and the main 
> function would be something like
>    do 
>       context <- getContext
>       doBusiness with context=context
> 

The catch is off course that every function with an explicit
type signature:

> explicit arguments -> IO result

needs a new type signature:

>  (?context :: Context) => explicit arguments -> IO result

Here, partial type declarations proposed by Koen Claessen would help.
Those declarations are quite usefull if one plans to use implicit
parameters a lot, allthough they improve flexibility in general. 
i.e. one could write:

... => explicit arguments -> IO result

all the time and add any extra implicit arguments as needed 
without change to existing source code.

All the best,
	Daan.






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