Re: foild function for expressions

Hi! I'm a begginer in haskell and I have a problem with an exercise, I expect
someone could help me:

In one hand I have a declaration of an algebra data, like this:

data AlgExp a = AlgExp
{ litI  :: Int -> a,
  litB :: Bool -> a,
  add :: a -> a -> a,
  and :: a -> a -> a,
  ifte :: a -> a -> a -> a}

(being ifte an 'ifthenelse' expresion...)

What I want to do is to write a fold function for expressions, something
like this:

foldExp :: AlgExp a -> Exp -> a
foldExp alg (LitI i) = litI alg i
foldExp alg (LitB i) = litB alg i
foldExp alg (add exp1 exp2) = ¿¿¿???
foldExp alg (and exp1 exp2) = ¿¿¿???
foldExp alg (ifte exp1 exp2 exp3) = ¿¿¿???