Cobham recursive set functions

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Cobham recursive set functions
This paper introduces the Cobham Recursive Set Functions (CRSF) as a version of polynomial time computable functions on general sets, based on a limited (bounded) form of ∈-recursion. This is inspired by Cobham’s classic definition of polynomial time functions based on limited recursion on notation. We introduce a new set composition function, and a new smash function for sets which allows polynomial increases in the ranks and in the cardinalities of transitive closures. We bootstrap CRSF, prove closure under (unbounded) replacement, and prove that any CRSF function is embeddable into a smash term. When restricted to natural encodings of binary strings as hereditarily finite sets, the CRSF functions define precisely the polynomial time computable functions on binary strings. Prior work of Beckmann, Buss and Friedman and of Arai introduced set functions based on safe-normal recursion in the sense of BellantoniCook. We prove an equivalence between our class CRSF and a variant of ...
Arnold Beckmann, Sam Buss, Sy-David Friedman, Mori
Added 29 Mar 2016
Updated 29 Mar 2016
Type Journal
Year 2016
Where APAL
Authors Arnold Beckmann, Sam Buss, Sy-David Friedman, Moritz Müller, Neil Thapen
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