Re: [Haskell-beginners] Decomposing recursion

Hello Russ Richard Kieburtz has a slightly smaller formulation of primitive recursion on page 13 of these slides - the fold-like argument 'h' doesn't appear to need a change of type: http://programatica.cs.pdx.edu/P/Programatica%20Logic1.pdf genPR :: (a -> Bool) -> (a -> a) -> c -> (a -> c -> c) -> a -> c genPR p b g h x = if p x then g else h x (genPR p b g h (b x)) -- factorial function: fact :: Integer -> Integer fact = genPR (==0) (subtract 1) 1 (*) Ignoring changes in argument order, the type of your recursionEngine is one term and one type variable larger: recursionEngine :: (a -> Bool) -> (a -> c) -> (b -> c -> c) -> (a -> b) -> (a -> a)-> a -> c Best wishes Stephen