Hi,
I'm trying to write a generic nominal abstract syntax library, and I
ran into a problem using ext1T. I asked around at #haskell but no one
was able to help me, I hope this is not too off topic here.
substAbs works just fine by itself, but when I try to combine it with
something using ext1T, it stops working. I can't figure out what's the
problem with this, am I doing something wrong?
*Main> substAbs $ a :\\: a
Name "a" (Just 1) :\\: Name "a" (Just 1)
*Main> id `ext1T` substAbs $ a :\\: a
Name "a" Nothing :\\: Name "a" Nothing
Here is my code:
>{-# LANGUAGE DeriveDataTypeable #-}
>
>import Data.Generics
>
>data Name = Name String (Maybe Int)
> deriving (Eq, Show, Data, Typeable)
>
>refresh (Name s Nothing) = Name s (Just 1)
>refresh (Name s (Just i)) = Name s (Just $ i+1)
>
>data Abs a = Name :\\: a deriving (Eq, Show, Data, Typeable)
>
>swapName (a,b) x = if a == x then b else
> if b == x then a else x
>
>swap (a,b) = everywhere (mkT $ swapName (a,b))
>
>substAbs (n :\\: x) = (m :\\: (x'))
> where m = refresh n
> x' = swap (n,m) x
>
>a = Name "a" Nothing
>b = Name "b" Nothing
Thanks in advance,
Daniel.
