Re: [Haskell-cafe] How to organize code

2008-01-28 Thread Jonathan Cast 

On 27 Jan 2008, at 11:18 PM, L.Guo wrote:


Hi,

How do you organize code ?

Here is a sample.
Acturally, I am thinking about using this plan.

Any suggestions ?


-- BasicalType.hs
type Position = (Int,Int)
data Box = Box { pos :: Position }
data Chain = Chain { pos :: [Position] }



-- Object.hs
import BasicalType
class Object o where
  pos :: o - [Position]



-- Type.hs
import BasicalType
import Object
instance Object Box where
  pos = return . BasicalType.pos
instance Object Chain where
  pos = BasicalType.pos



-- Main.hs
import Type
...


I would recommend against this; Type.hs should define the types  
directly, and define or import the Object class.


In particular, IIRC GHC wants ever instance in the same module as  
either the type or the class definition, for performance reasons  
(this is the most common pattern, so it gets special optimizations).


jcc

___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe

[Haskell-cafe] How to organize code

2008-01-27 Thread L.Guo 
Hi,

How do you organize code ?

Here is a sample.
Acturally, I am thinking about using this plan.

Any suggestions ?

 -- BasicalType.hs
 type Position = (Int,Int)
 data Box = Box { pos :: Position }
 data Chain = Chain { pos :: [Position] }

 -- Object.hs
 import BasicalType
 class Object o where
   pos :: o - [Position]

 -- Type.hs
 import BasicalType
 import Object
 instance Object Box where
   pos = return . BasicalType.pos
 instance Object Chain where
   pos = BasicalType.pos

 -- Main.hs
 import Type
 ...

Regards
--
L.Guo
2008-01-28

___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe

Re: [Haskell-cafe] How to organize code

2008-01-27 Thread Tim Chevalier 
On 1/27/08, L.Guo [EMAIL PROTECTED] wrote:
 Hi,

 How do you organize code ?

 Here is a sample.
 Acturally, I am thinking about using this plan.

 Any suggestions ?

  -- BasicalType.hs
  type Position = (Int,Int)
  data Box = Box { pos :: Position }
  data Chain = Chain { pos :: [Position] }

  -- Object.hs
  import BasicalType
  class Object o where
pos :: o - [Position]

  -- Type.hs
  import BasicalType
  import Object
  instance Object Box where
pos = return . BasicalType.pos
  instance Object Chain where
pos = BasicalType.pos

  -- Main.hs
  import Type
  ...


Be careful not to confuse Haskell's type class system with the idea of
a class in object-oriented programming. I suggest you read this
article:
http://trevion.blogspot.com/2007/02/snowball-chance.html

Cheers,
Tim

-- 
Tim Chevalier * http://cs.pdx.edu/~tjc * Often in error, never in doubt
...It's a thin line between amateur and professional, a line mostly
emphasized by insecure professionals. -- Bob Franke
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe