3,339 research outputs found
Syntax for free: representing syntax with binding using parametricity
We show that, in a parametric model of polymorphism, the type ββΞ±.β((Ξ±βββΞ±)βββΞ±)βββ(Ξ±βββΞ±βββΞ±)βββΞ± is isomorphic to closed de Bruijn terms. That is, the type of closed higher-order abstract syntax terms is isomorphic to a concrete representation. To demonstrate the proof we have constructed a model of parametric polymorphism inside the Coq proof assistant. The proof of the theorem requires parametricity over Kripke relations. We also investigate some variants of this representation
Scalar and Vectorial mu-calculus with Atoms
We study an extension of modal -calculus to sets with atoms and we study
its basic properties. Model checking is decidable on orbit-finite structures,
and a correspondence to parity games holds. On the other hand, satisfiability
becomes undecidable. We also show expressive limitations of atom-enriched
-calculi, and explain how their expressive power depends on the structure
of atoms used, and on the choice between basic or vectorial syntax
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