Finitary Corecursion for the Infinitary Lambda Calculus

Authors Stefan Milius, Thorsten Wißmann

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Stefan Milius
Thorsten Wißmann

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Stefan Milius and Thorsten Wißmann. Finitary Corecursion for the Infinitary Lambda Calculus. In 6th Conference on Algebra and Coalgebra in Computer Science (CALCO 2015). Leibniz International Proceedings in Informatics (LIPIcs), Volume 35, pp. 336-351, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)


Kurz et al. have recently shown that infinite lambda-trees with finitely many free variables modulo alpha-equivalence form a final coalgebra for a functor on the category of nominal sets. Here we investigate the rational fixpoint of that functor. We prove that it is formed by all rational lambda-trees, i.e. those lambda-trees which have only finitely many subtrees (up to isomorphism). This yields a corecursion principle that allows the definition of operations such as substitution on rational lambda-trees.
  • rational trees
  • infinitary lambda calculus
  • coinduction


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