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On the synthesis of function inverses

Peter G. Harrison, Hessam Khoshnevisan

Journal Article
Acta Informatica
Volume 29
Issue 3
March, 1992
Springer Verlag
DOI 10.1007/BF01185679

We present a method for synthesising recursive inverses for first-order functions. Since inverse functions are not, in general, single-valued, we introduce a powerdomain to define their semantics, in terms of which we express their transformation into recursive form. First, inverses that require unification at run-time are synthesised and these are then optimised by term-rewriting based on a set of axioms that facilitates a form of compile-time unification. The optimisations reduce the dependency on run-time unification, in many instances removing it entirely to give a recursive inverse. The efficiency of the use of relations in two modes is thereby improved, so enhencing extended functional languages endowed with logical variables and narrowing semantics. Our function-level, axiomatised system is more generally applicable than previous approaches to this type of optimis tion, and in general induces more mechanisable transformation systems.

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