I'm not sure if you got my previous message, as I was having some problems posting to the list...
Putting in a nutshell, I generalize an extensional defined function definition into a recursive one. This is done in a number of steps by modifying expressions and exploiting type information of sub-expressions. For example:
rev [] = [] rev [a] = [a] rev [a,b] = [b,a] rev [a,b,c] = [c,b,a]
~~>
rev x = y
~~>
rev [] = [] rev (x:xs) = (y:ys)
~~>
rev [] = [] rev (x:xs) = (last (x:xs)) : (reverse (x:xs))
The initial set of rules is given by the user (in a file, via IO, ...). The problem later is to infer the type of an intermediate variable, e.g. 'y'.
I'm still not entirely sure what you want to do here. But it sounds like HaRe could already do most of this for you via a sequence of folds, unfolds, introduce pattern matching and generative folding. HaRe already has built-in support for some symbolic evaluation, which is already used in the generative fold refactoring, and has type checking support too. http://www.cs.kent.ac.uk/projects/refactor-fp/hare.html If it doesn't do exactly what you want out of the tin, it does have a large API for designing transformations over Haskell code. http://www.cs.kent.ac.uk/projects/refactor-fp/hare/haddock/RefacUtils.html Chris.
Thanks,
Martin
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