An Algebra for Higher-Order Terms

Lars Hupel with contributions from Yu Zhang

15 January 2019


In this formalization, I introduce a higher-order term algebra, generalizing the notions of free variables, matching, and substitution. The need arose from the work on a verified compiler from Isabelle to CakeML. Terms can be thought of as consisting of a generic (free variables, constants, application) and a specific part. As example applications, this entry provides instantiations for de-Bruijn terms, terms with named variables, and Blanchette’s λ-free higher-order terms. Furthermore, I implement translation functions between de-Bruijn terms and named terms and prove their correctness.
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