I didn't test it, but you might want to look into the 'rebindable syntax'
extension and its 'ifThenElse' feature.
Nicolas
On Sep 2, 2013 12:51 AM, "Wvv"
I think it is an old idea, but nevertheless. Now we have next functions:
if (a :: Bool) then x else y
case b of a1 :: Bool -> x1 a2 :: Bool -> x2 ...
Let we have generic conditions for 'if' and 'case':
class Boolean a where toBool :: a -> Bool
instance Boolean Bool where toBool = id
instance Boolean [a] where toBool [] = False toBool _ = True
instance Boolean (Maybe a) where toBool Nothing = False toBool _ = True
instance Boolean Int where toBool 0 = False toBool _ = True
if' (a :: Boolean b) then x else y
case' d of a1 :: Boolean b1 -> x1 a2 :: Boolean b2 -> x2 ...
It is very easy to implement to desugar: if' a then ... == if toBool ( a ) then ...
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