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arXiv · 2102.08146

Nominal Unification and Matching of Higher Order Expressions with Recursive Let

Manfred Schmidt-Schauß·Temur Kutsia·Jordi Levy·Mateu Villaret·Yunus Kutz
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Abstract

A sound and complete algorithm for nominal unification of higher-order expressions with a recursive let is described, and shown to run in nondeterministic polynomial time. We also explore specializations like nominal letrec-matching for expressions, for DAGs, and for garbage-free expressions and determine their complexity. We also provide a nominal unification algorithm for higher-order expressions with recursive let and atom-variables, where we show that it also runs in nondeterministic polynomial time. In addition we prove that there is a guessing strategy for nominal unification with letrec and atom-variable that is a trade-off between exponential growth and non-determinism. Nominal matching with variables representing partial letrec-environments is also shown to be in NP.

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Manfred Schmidt-Schauß, Temur Kutsia, Jordi Levy, Mateu Villaret, Yunus Kutz. 2021-02-16. Nominal Unification and Matching of Higher Order Expressions with Recursive Let. https://doi.org/10.3233/fi-222110

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