scholarly journals Non-primitive Recursive Function Definitions

1995 ◽  
Vol 2 (36) ◽  
Author(s):  
Sten Agerholm
Keyword(s):  
Recursive Function ◽  
Higher Order ◽  
Order Logic ◽  
Domain Theory ◽  
Higher Order Logic ◽  
Primitive Recursive Function ◽  
Primitive Recursive

This paper presents an approach to the problem of introducing<br />non-primitive recursive function definitions in higher order logic. A<br />recursive specification is translated into a domain theory version, where<br />the recursive calls are treated as potentially non-terminating. Once we<br />have proved termination, the original specification can be derived easily.<br />A collection of algorithms are presented which hide the domain theory<br />from a user. Hence, the derivation of a domain theory specification<br />has been automated completely, and for well-founded recursive function<br />specifications the process of deriving the original specification from the<br />domain theory one has been automated as well, though a user must<br />supply a well-founded relation and prove certain termination properties<br />of the specification. There are constructions for building well-founded<br />relations easily.

scholarly journals A HOL Basis for Reasoning about Functional Programs

1994 ◽  
Vol 1 (44) ◽  
Author(s):  
Sten Agerholm
Keyword(s):  
Higher Order ◽  
Partial Orders ◽  
Order Logic ◽  
Domain Theory ◽  
Higher Order Logic ◽  
Unification Algorithm ◽  
Recursive Functions ◽  
Bottom Element ◽  
Definition Of ◽  
Primitive Recursive

Domain theory is the mathematical theory underlying denotational semantics. This thesis presents a formalization of domain theory in the Higher Order Logic (HOL) theorem proving system along with a mechanization of proof functions and other tools to support reasoning about the denotations of functional programs. By providing a fixed point operator for functions on certain domains which have a special undefined (bottom) element, this extension of HOL supports the definition of recursive functions which are not also primitive recursive. Thus, it provides an approach to the long-standing and important problem of defining non-primitive recursive functions in the HOL system.<br /> <br />Our philosophy is that there must be a direct correspondence between elements of complete partial orders (domains) and elements of HOL types, in order to allow the reuse of higher order logic and proof infrastructure already available in the HOL system. Hence, we are able to mix domain theoretic reasoning with reasoning in the set theoretic HOL world to advantage, exploiting HOL types and tools directly. Moreover, by mixing domain and set theoretic reasoning, we are able to eliminate almost all reasoning about the bottom element of complete partial orders that makes the LCF theorem prover, which supports a first order logic of domain theory, difficult and tedious to use. A thorough comparison with LCF is provided.<br /> <br />The advantages of combining the best of the domain and set theoretic worlds in the same system are demonstrated in a larger example, showing the correctness of a unification algorithm. A major part of the proof is conducted in the set theoretic setting of higher order logic, and only at a late stage of the proof domain theory is introduced to give a recursive definition of the algorithm, which is not primitive recursive. Furthermore, a total well-founded recursive unification function can be defined easily in pure HOL by proving that the unification algorithm (defined in domain theory) always terminates; this proof is conducted by a non-trivial well-founded induction. In such applications, where non-primitive recursive HOL functions are defined via domain theory and a proof of termination, domain theory constructs only appear temporarily.

scholarly journals Closed Structure

2021 ◽  
Author(s):  
Peter Fritz ◽  
Harvey Lederman ◽  
Gabriel Uzquiano
Keyword(s):  
Formal Language ◽  
Syntactic Structure ◽  
Natural Extension ◽  
Propositional Attitudes ◽  
Higher Order ◽  
Order Logic ◽  
Bertrand Russell ◽  
Structured Propositions ◽  
Higher Order Logic ◽  
Closed Structure

AbstractAccording to the structured theory of propositions, if two sentences express the same proposition, then they have the same syntactic structure, with corresponding syntactic constituents expressing the same entities. A number of philosophers have recently focused attention on a powerful argument against this theory, based on a result by Bertrand Russell, which shows that the theory of structured propositions is inconsistent in higher order-logic. This paper explores a response to this argument, which involves restricting the scope of the claim that propositions are structured, so that it does not hold for all propositions whatsoever, but only for those which are expressible using closed sentences of a given formal language. We call this restricted principle Closed Structure, and show that it is consistent in classical higher-order logic. As a schematic principle, the strength of Closed Structure is dependent on the chosen language. For its consistency to be philosophically significant, it also needs to be consistent in every extension of the language which the theorist of structured propositions is apt to accept. But, we go on to show, Closed Structure is in fact inconsistent in a very natural extension of the standard language of higher-order logic, which adds resources for plural talk of propositions. We conclude that this particular strategy of restricting the scope of the claim that propositions are structured is not a compelling response to the argument based on Russell’s result, though we note that for some applications, for instance to propositional attitudes, a restricted thesis in the vicinity may hold some promise.

Adapting functional programs to higher order logic

2008 ◽  
Vol 21 (4) ◽  
pp. 377-409 ◽  
Author(s):  
Scott Owens ◽  
Konrad Slind
Keyword(s):  
Higher Order ◽  
Order Logic ◽  
Higher Order Logic

scholarly journals “How did the serpent of inconsistency enter Frege’s paradise?”

2019 ◽  
pp. 411-436
Author(s):  
Crispin Wright
Keyword(s):  
Cardinal Number ◽  
Ordinal Number ◽  
Higher Order ◽  
Order Logic ◽  
Higher Order Logic ◽  
Indefinite Extensibility ◽  
Basic Law ◽  
Per Se

The paper explores the alleged connection between indefinite extensibility and the classic paradoxes of Russell, Burali-Forti, and Cantor. It is argued that while indefinite extensibility is not per se a source of paradox, there is a degenerate subspecies—reflexive indefinite extensibility—which is. The result is a threefold distinction in the roles played by indefinite extensibility in generating paradoxes for the notions of ordinal number, cardinal number, and set respectively. Ordinal number, intuitively understood, is a reflexively indefinitely extensible concept. Cardinal number is not. And Set becomes so only in the setting of impredicative higher-order logic—so that Frege’s Basic Law V is guilty at worst of partnership in crime, rather than the sole offender.

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