Hi,
The runtime behaviour of the two modules below *seems* to be the same.
Is this correct?
I am not trying to say "every building is a shelter", rather "anything that is a building must provide sheltering services".
I think that the use of sub-classes makes this explicit, but it *seems* that one gets the same results without the subclass.
Any clarification welcome.
Regards,
Pat
-- ========================================
module WithSubclass where
data SomeWhereToShelter = SomeWhereToShelter
class Shelter shelter where
s :: shelter -> String
class Shelter building => Building building where
b :: building -> String
class Shelter house => House house where
h :: house -> String
instance Shelter SomeWhereToShelter where
s x = "Shelters afford basic sheltering"
instance Building SomeWhereToShelter where
b x = (s x) ++ ", Buildings afford better sheltering"
instance House SomeWhereToShelter where
h x = (s x) ++ (b x) ++ ", Houses afford even better sheltering"
-- =======================================
module WithoutSubclass where
data SomeWhereToShelter = SomeWhereToShelter
class Shelter shelter where
s :: shelter -> String
class Building building where
b :: building -> String
class House house where
h :: house -> String
instance Shelter SomeWhereToShelter where
s x = "Shelters afford basic sheltering"
instance Building SomeWhereToShelter where
b x = (s x) ++ ", Buildings afford better sheltering"
instance House SomeWhereToShelter where
h x = (s x) ++ (b x) ++ ", Houses afford even better sheltering"
The runtime behaviour of the two modules below *seems* to be the same.
Is this correct?
I am not trying to say "every building is a shelter", rather "anything that is a building must provide sheltering services".
I think that the use of sub-classes makes this explicit, but it *seems* that one gets the same results without the subclass.
Any clarification welcome.
Regards,
Pat
-- ========================================
module WithSubclass where
data SomeWhereToShelter = SomeWhereToShelter
class Shelter shelter where
s :: shelter -> String
class Shelter building => Building building where
b :: building -> String
class Shelter house => House house where
h :: house -> String
instance Shelter SomeWhereToShelter where
s x = "Shelters afford basic sheltering"
instance Building SomeWhereToShelter where
b x = (s x) ++ ", Buildings afford better sheltering"
instance House SomeWhereToShelter where
h x = (s x) ++ (b x) ++ ", Houses afford even better sheltering"
-- =======================================
module WithoutSubclass where
data SomeWhereToShelter = SomeWhereToShelter
class Shelter shelter where
s :: shelter -> String
class Building building where
b :: building -> String
class House house where
h :: house -> String
instance Shelter SomeWhereToShelter where
s x = "Shelters afford basic sheltering"
instance Building SomeWhereToShelter where
b x = (s x) ++ ", Buildings afford better sheltering"
instance House SomeWhereToShelter where
h x = (s x) ++ (b x) ++ ", Houses afford even better sheltering"
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