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DOI: 10.4230/LIPIcs.TYPES.2023.2

Finite Combinatory Logic with Predicates

Authors: Andrej Dudenhefner, Christoph Stahl, Constantin Chaumet, Felix Laarmann, and Jakob Rehof

Published in: LIPIcs, Volume 303, 29th International Conference on Types for Proofs and Programs (TYPES 2023)

Abstract

Type inhabitation in extensions of Finite Combinatory Logic (FCL) is the mechanism underlying various component-oriented synthesis frameworks. In FCL inhabitant sets correspond to regular tree languages and vice versa. Therefore, it is not possible to specify non-regular properties of inhabitants, such as (dis)equality of subterms. Additionally, the monomorphic nature of FCL oftentimes hinders concise specification of components. We propose a conservative extension to FCL by quantifiers and predicates, introducing a restricted form of polymorphism. In the proposed type system (FCLP) inhabitant sets correspond to decidable term languages and vice versa. As a consequence, type inhabitation in FCLP is undecidable. Based on results in tree automata theory, we identify a fragment of FCLP with the following two properties. First, the fragment enjoys decidable type inhabitation. Second, it allows for specification of local (dis)equality constraints for subterms of inhabitants. For empirical evaluation, we implement a semi-decision procedure for type inhabitation in FCLP. We compare specification capabilities, scalability, and performance of the implementation to existing FCL-based approaches. Finally, we evaluate practical applicability via a case study, synthesizing mechanically sound robotic arms.

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Andrej Dudenhefner, Christoph Stahl, Constantin Chaumet, Felix Laarmann, and Jakob Rehof. Finite Combinatory Logic with Predicates. In 29th International Conference on Types for Proofs and Programs (TYPES 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 303, pp. 2:1-2:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{dudenhefner_et_al:LIPIcs.TYPES.2023.2,
  author =	{Dudenhefner, Andrej and Stahl, Christoph and Chaumet, Constantin and Laarmann, Felix and Rehof, Jakob},
  title =	{{Finite Combinatory Logic with Predicates}},
  booktitle =	{29th International Conference on Types for Proofs and Programs (TYPES 2023)},
  pages =	{2:1--2:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-332-4},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{303},
  editor =	{Kesner, Delia and Reyes, Eduardo Hermo and van den Berg, Benno},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.TYPES.2023.2},
  URN =		{urn:nbn:de:0030-drops-204808},
  doi =		{10.4230/LIPIcs.TYPES.2023.2},
  annote =	{Keywords: combinatory logic, inhabitation, intersection types, program synthesis}
}

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DOI: 10.4230/LIPIcs.FSCD.2022.14

Restricting Tree Grammars with Term Rewriting

Authors: Jan Bessai, Lukasz Czajka, Felix Laarmann, and Jakob Rehof

Published in: LIPIcs, Volume 228, 7th International Conference on Formal Structures for Computation and Deduction (FSCD 2022)

Abstract

We investigate the problem of enumerating all terms generated by a tree-grammar which are also in normal form with respect to a set of directed equations (rewriting relation). To this end we show that deciding emptiness and finiteness of the resulting set is EXPTIME-complete. The emptiness result is inspired by a prior result by Comon and Jacquemard on ground reducibility. The finiteness result is based on modification of pumping arguments used by Comon and Jacquemard. We highlight practical applications and limitations. We provide and evaluate a prototype implementation. Limitations are somewhat surprising in that, while deciding emptiness and finiteness is EXPTIME-complete for linear and nonlinear rewrite relations, the linear case is practically feasible while the nonlinear case is infeasible, even for a trivially small example. The algorithms provided for the linear case also improve on prior practical results by Kallat et al.

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Jan Bessai, Lukasz Czajka, Felix Laarmann, and Jakob Rehof. Restricting Tree Grammars with Term Rewriting. In 7th International Conference on Formal Structures for Computation and Deduction (FSCD 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 228, pp. 14:1-14:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{bessai_et_al:LIPIcs.FSCD.2022.14,
  author =	{Bessai, Jan and Czajka, Lukasz and Laarmann, Felix and Rehof, Jakob},
  title =	{{Restricting Tree Grammars with Term Rewriting}},
  booktitle =	{7th International Conference on Formal Structures for Computation and Deduction (FSCD 2022)},
  pages =	{14:1--14:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-233-4},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{228},
  editor =	{Felty, Amy P.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSCD.2022.14},
  URN =		{urn:nbn:de:0030-drops-162953},
  doi =		{10.4230/LIPIcs.FSCD.2022.14},
  annote =	{Keywords: tree automata, tree grammar, term rewriting, normalization, emptiness, finiteness}
}

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Documents authored by Laarmann, Felix

Finite Combinatory Logic with Predicates

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Restricting Tree Grammars with Term Rewriting

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