Unifying Structured Recursion Schemes Ralf Hinze Nicolas Wu Jeremy Gibbons Department of Computer Science, University of Oxford, Wolfson Building, Parks Road, Oxford, OX1 3QD, England {ralf.hinze,nicolas.wu,jeremy.gibbons}@cs.ox.ac.uk Abstract Folds over inductive datatypes are well understood and widely used. In their plain form, they are quite restricted; but many dis- parate generalisations hav