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Automatic Synthesis of Recursive Programs: The ProofPlanning Paradigm
, 1997
"... We describe a proof plan that characterises a family of proofs corresponding to the synthesis of recursive functional programs. This plan provides a significant degree of automation in the construction of recursive programs from specifications, together with correctness proofs. This plan makes use o ..."
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Cited by 21 (2 self)
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We describe a proof plan that characterises a family of proofs corresponding to the synthesis of recursive functional programs. This plan provides a significant degree of automation in the construction of recursive programs from specifications, together with correctness proofs. This plan makes use of metavariables to allow successive refinement of the identity of unknowns, and so allows the program and the proof to be developed hand in hand. We illustrate the plan with parts of a substantial example  the synthesis of a unification algorithm.
Type Inference Verified: Algorithm W in Isabelle/HOL
, 1997
"... This paper presents the first machinechecked verification of Milner's type inference algorithm W for computing the most general type of an untyped term enriched with letexpressions. This term language is the core of most typed functional programming languages and is also known as MiniML. We ..."
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Cited by 15 (1 self)
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This paper presents the first machinechecked verification of Milner's type inference algorithm W for computing the most general type of an untyped term enriched with letexpressions. This term language is the core of most typed functional programming languages and is also known as MiniML. We show how to model all the concepts involved, in particular types and type schemes, substitutions, and the thorny issue of "new" variables. Only a few key proofs are discussed in detail. The theories and proofs are developed in Isabelle/HOL, the HOL instantiation of the generic theorem prover Isabelle.
Program verification
 Journal of Automated Reasoning
, 1985
"... Computer programs may be regarded as formal mathematical objects whose properties are subject to mathematical proof. Program verification is the use of formal, mathematical techniques to debug software and software specifications. 1. Code Verification How are the properties of computer programs prov ..."
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Cited by 14 (4 self)
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Computer programs may be regarded as formal mathematical objects whose properties are subject to mathematical proof. Program verification is the use of formal, mathematical techniques to debug software and software specifications. 1. Code Verification How are the properties of computer programs proved? We discuss three approaches in this article: inductive invariants, functional semantics, and explicit semantics. Because the first approach has received by far the most attention, it has produced the most impressive results to date. However, the field is now moving away from the inductive invariant approach. 1.1. Inductive Assertions The socalled FloydHoare inductive assertion method of program verification [25, 33] has its roots in the classic Goldstine and von Neumann reports [53] and handles the usual kind of programming language, of which FORTRAN is perhaps the best example. In this style of verification, the specifier "annotates " certain points in the program with mathematical assertions that are supposed to describe relations that hold between the program variables and the initial input values each time "control " reaches the annotated point. Among these assertions are some that characterize acceptable input and the desired output. By exploring all possible paths from one assertion to the next and analyzing the effects of intervening program statements it is possible to reduce the correctness of the program to the problem of proving certain derived formulas called verification conditions. Below we illustrate the idea with a simple program for computing the factorial of its integer input N flowchart assertion start with input(N) input N A: = 1 N = 0 yes stop with? answer A
LCF Examples in HOL
 The Computer Journal
, 1994
"... The LCF system provides a logic of fixed point theory and is useful to reason about nontermination, recursive definitions and infinitevalued types such as lazy lists. Because of continual presence of bottom elements, it is clumsy for reasoning about finitevalued types and strict functions. The ..."
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Cited by 12 (4 self)
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The LCF system provides a logic of fixed point theory and is useful to reason about nontermination, recursive definitions and infinitevalued types such as lazy lists. Because of continual presence of bottom elements, it is clumsy for reasoning about finitevalued types and strict functions. The HOL system provides set theory and supports reasoning about finitevalued types and total functions well. In this paper a number of examples are used to demonstrate that an extension of HOL with domain theory combines the benefits of both systems. The examples illustrate reasoning about infinite values and nonterminating functions and show how domain and set theoretic reasoning can be mixed to advantage. An example presents a proof of correctness of a recursive unification algorithm using wellfounded induction.
Induction Proofs with Partial Functions
 Journal of Automated Reasoning
, 1998
"... In this paper we present a method for automated induction proofs about partial functions. We show that most wellknown techniques developed for (explicit) induction theorem proving are unsound when dealing with partial functions. But surprisingly, by slightly restricting the application of these te ..."
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Cited by 5 (4 self)
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In this paper we present a method for automated induction proofs about partial functions. We show that most wellknown techniques developed for (explicit) induction theorem proving are unsound when dealing with partial functions. But surprisingly, by slightly restricting the application of these techniques, it is possible to develop a calculus for automated induction proofs with partial functions. In particular, under certain conditions one may even generate induction schemes from the recursions of nonterminating algorithms. The need for such induction schemes and the power of our calculus have been demonstrated on a large collection of nontrivial theorems (including Knuth and Bendix' critical pair lemma). In this way, existing induction theorem provers can be directly extended to partial functions without major changes of their logical framework.