A recursion theoretic foundation of computation over real numbers

10/02/2020

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by   Keng Meng Ng, et al.

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We define a class of computable functions over real numbers using functional schemes similar to the class of primitive and partial recursive functions defined by Gödel and Kleene. We show that this class of functions can also be characterized by master-slave machines, which are Turing machine like devices. The proof of the characterization gives a normal form theorem in the style of Kleene. Furthermore, this characterization is a natural combination of two most influential theories of computation over real numbers, namely, the type-two theory of effectivity (TTE) (see, for example, Weihrauch) and the Blum-Shub-Smale model of computation (BSS). Under this notion of computability, the recursive (or computable) subsets of real numbers are exactly effective Δ^0_2 sets.