Re: [Haskell-cafe] subclasses and classes with same type in instance

2011-10-18 Thread Albert Y. C. Lai 

On 11-10-16 01:56 PM, Patrick Browne wrote:

I get the same results from Listing 1 and Listing 2 below.


I carefully diff'ed the two listings and found no difference except for 
comments.



-- Listing 1- Subclass
data Shed = Shed

class Building building where
  addressB :: building - Integer
  addressB b = 1

--  subclass, but none in Listing 2
class Building house = House house where
  addressH :: house - Integer
  addressH b = 0

instance Building Shed where
instance House Shed where


-- Listing 2 -- No subclass
data Shed = Shed

class Building building where
  addressB :: building - Integer
  addressB b = 1

-- No subclass
class Building house = House house where
  addressH :: house - Integer
  addressH b = 0

instance Building Shed where
instance House Shed where


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[Haskell-cafe] subclasses and classes with same type in instance

2011-10-16 Thread Patrick Browne 
Hi,Does the subclass relation have any meaning when two classes have instances with the same type?I get the same results from Listing 1 and Listing 2 below.Regards,Pat-- Listing 1- Subclassdata Shed = Shed class Building building where addressB :: building - Integer addressB b = 1--  subclass, but none in Listing 2class Building house = House house where addressH :: house - Integer addressH b = 0instance Building Shed whereinstance House Shed where-- Listing 2 -- No subclassdata Shed = Shed class Building building where addressB :: building - Integer addressB b = 1-- No subclass class Building house = House house where addressH :: house - Integer addressH b = 0instance Building Shed whereinstance House Shed where-- Test runs give same result for Listing 1 and Listing 2--  addressH Shed--  addressB Shed

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