20 Sep
2011
20 Sep
'11
7:31 p.m.
On Wednesday 21 September 2011, 01:02:52, wagnerdm@seas.upenn.edu wrote:
Would it be possible to have no command at all? Types are distinguished by upper-case letters, so it should be possible to tell whether a given expression is a value-level or a type-level expression.
Unless I'm misunderstanding, no: {-# LANGUAGE TypeFamilies #-} module TFEx where type family F a type instance F Int = Bool type instance F Bool = Int type instance F (a, b) = (F a, F b) data Foo a = F a deriving Show data Moo = Int | Bool deriving Show *TFEx> F (Int,Bool) F (Int,Bool) *TFEx> :t F (Int,Bool) F (Int,Bool) :: Foo (Moo, Moo) *TFEx> :t undefined :: F (Int,Bool) undefined :: F (Int,Bool) :: (Bool, Int) *TFEx>