The :info command is a great help. Why does :info g 4 produce a parse error, while :t g 4 does not? Thanks for all your help, Pat On 13/08/2011 00:08, Brandon Allbery wrote:
Typeclasses are not independent of types, and are not inferred separately from types. If you want to know what typeclasses a type is a member of, use :info.
On 12/08/2011 23:52, Patrick Browne wrote:
Hi, Why does the Haskell :type command only sometimes print the type-class? Should I expect type-class inference as well as type inference? Maybe the type-class is inferred where possible, but not always printed?
Thanks, Pat
-- Code k x = x + 3
data T = T class A a where g::a -> a g a = a instance A T where instance A Integer where
-- The results from the above code. -- First in the case of a function. Inferred the Num class *Main> :t k k :: forall a. (Num a) => a -> a *Main> :t k 3 k 3 :: forall t. (Num t) => t -- Did not print type class *Main> :t k (3::Integer) k (3::Integer) :: Integer
-- Second in the case of a method of a type class. -- Inferred Num *Main> :t g 3 g 3 :: forall t. (A t, Num t) => t -- Did not print class A. *Main> :t g T g T :: T -- Did not print any class. *Main> :t g (3::Integer) g (3::Integer) :: Integer
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