We review some of the history of the computability theory of functionals of higher types, and we will demonstrate how contributions from logic and theoretical computer science hav...
We give a self-contained and streamlined version of the classification of the provably computable functions of PA. The emphasis is put on illuminating as good as seems possible th...
We show that each of the five basic theories of second order arithmetic that play a central role in reverse mathematics has a natural counterpart in the language of nonstandard ari...