hirarchical modules

[Iavor Diatchki]

hello,

Hal Daume III wrote:
> This was brought up before:
> 
>   http://www.haskell.org/pipermail/libraries/2002-February/000552.html
> 
> and then again before that I think I wrote something about it, but can't
> find the message.  Needless to say, I think this would be *very* nice, but
> there didn't seem to be support from the powers that be.

i am aware that there have been previous discussions on the subject,
but they seem to have had no results (who are the powers that be? :-). 
and i could see no good reason as to why. simply because simon doesn't 
mind writing out 40 character imports doesn't mean that we have a good 
design.

the flaws i pointed out seemed kind of obvious. perhaps i should be more 
concrete.  here is an example:

 > module Control.Monad.Experimental.State
 >   (State,
 >    Control.Monad.Experimental.State.runState,
 >    Control.Monad.Experimental.State.runStateS,
 >   module T) where
 >
 > import Control.Monad.Experimental.Identity
 > import Control.Monad.Experimental.StateT as S
 > import Control.Monad.Experimental.Trans as T
 >
 > type State s  = StateT s Identity
 >
 > runState      :: s -> State s a -> a
 > runState s m  = runIdentity (S.runState s m)
 >
 > runStateS     :: s -> State s a -> (a,s)
 > runStateS s m = runIdentity (S.runStateS s m)

suggestions on how to rewrite the imports/exports above more concisely 
are welcome.  by the way the changes i suggested before (and i am sure 
others must have pointed out) would allow me to write this module in the 
usual haskell way (which at least in this case seems vastly superior).
and then the module would be compatable with systems that do not 
implement the hirarchical module extension.

bye
iavor


> 
> As for moving things around, the suggestion I got was to use a quick
> 'grep' to change the module names :).  Very efficient.
> 
>  - Hal
> 
> --
>  Hal Daume III                                   | hdaume@isi.edu
>  "Arrest this man, he talks in maths."           | www.isi.edu/~hdaume
> 
> On Wed, 28 May 2003, Iavor Diatchki wrote:
> 
> 
>>hello,
>>
>>i was wondering how final is the design of the hirarchical module system 
>>for haskell?  i have been working on the monad library for the past week 
>>or so and this is my first experience with the hirarchical module system
>>in a real project. i must say that i find it very cumbersome.
>>
>>here is why:  the whole monadic library is in the same directory, but 
>>since there is no way to use relative names, all the imports use the 
>>rather long fully qualified name.  things like:
>>
>>import Control.Monad.X.ReaderT
>>
>>are very common. and if the hirarchy gets deeper, names will get longer.
>>while the verbosilty is annoying there is a more serious problem. 
>>moving code around is very work intensive (and error prone).  for 
>>example, when i decide that what i have is stable enough i'd like to 
>>move it to the Control.Monad part of the library (i.e. get rid of the 
>>X).  that means that i have to go and change all the imports, and all 
>>the module names.
>>
>>of course i have a haskell lexer at my disposition so i have a little 
>>program to do that for me, but that solution seems very unsatisfactory.
>>
>>and there seems to be a rather obvious solution to this problem:
>>1. allow for imports relative to the location of the importing module
>>2. remove the requirement that the path to a module is hardcoded in the 
>>module name.
>>
>>i am now hoping that someone will say: yes we already tought of that and 
>>it is indeed supported...
>>any thoughts?
>>
>>bye
>>iavor
>>
>>
>>
>>
>>
>>
>>
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> 
>