Using Middle-Out Reasoning to Control the Synthesis of Tail-Recursive Programs

J. Hesketh, Alan Bundy, A. Smaill

Research output: Chapter in Book/Report/Conference proceedingConference contribution


We describe a novel technique for the automatic synthesis of tail-recursive programs. The technique is to specify the required program using the standard equations and then synthesise the tail-recursive program using the proofs as programs technique. This requires the specification to be proved realisable in a constructive logic. Restrictions on the form of the proof ensure that the synthesised program is tail-recursive.

The automatic search for a synthesis proof is controlled by proof plans, which are descriptions of the high-level structure of proofs of this kind. We have extended the known proof plans for inductive proofs by adding a new form of generalisation and by making greater use of middle-out reasoning. In middle-out reasoning we postpone decisions in the early part of the proof by the use of meta-variables which are instantiated, by unification, during later parts of the proof. Higher order unification is required, since these meta-variables can represent higher order objects.

The program synthesised is automatically verified to ensure that it satisfies its specification. This type of verification is contrasted with template-based transformation approaches which require proofs that the general transformations described by the templates preserve equivalence.
The technique described is more general than template-based approaches, since it is not tied to program patterns which must be specified in advance. Detailed information about proof structure enables it to use a wider repertoire of rewritings in a more goal-directed way than comparable transformational techniques.
Original languageEnglish
Title of host publicationAutomated Deduction—CADE-11
Subtitle of host publication11th International Conference on Automated Deduction Saratoga Springs, NY, USA, June 15–18, 1992 Proceedings
PublisherSpringer Berlin Heidelberg
Number of pages15
ISBN (Electronic)978-3-540-47252-0
ISBN (Print)978-3-540-55602-2
Publication statusPublished - 1992

Publication series

NameLecture Notes in Computer Science
PublisherSpringer Berlin Heidelberg
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


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