Hi, I was reading the paper "Total Functional Programming" [1]. I encountered an interesting note on p. 759 that primitive recursion in a higher-order language allows defining much larger set of function than classical primitive recursion (which, for example, cannot define Ackermann's function). And that this is studied in in Gödel's System T. It also states that this larger set of primitive functions includes all functions whose totality can be proved in first order logic. I was searching the Internet but I couldn't find a resource (a paper, a book) that would explain this in detail, give proofs etc. I'd be happy if someone could give me some directions. Thanks, Petr [1] http://www.jucs.org/jucs_10_7/total_functional_programming/jucs_10_07_0751_0...