Andrej Bauer, Martin Hofmann and Aleksandr Karbyshev. On Monadic Parametricity of Second-Order Functionals. In Frank Pfenning, editor, FoSSaCS, volume 7794 of Lecture Notes in Computer Science, pages 225-240, March 2013. Springer.

How can one rigorously specify that a given ML functional $f : (int \to int) \to int$ is pure, i.e., $f$ produces no computational effects except those produced by evaluation of its functional argument? In this paper, we introduce a semantic notion of monadic parametricity for second-order functionals which is a form of purity. We show that every monadically parametric $f$ admits a question-answer strategy tree representation. We discuss possible applications of this notion, e.g., to the verification of generic fixpoint algorithms. The results are presented in two settings: a total set-theoretic setting and a partial domain-theoretic one. All proofs are formalized by means of the proof assistant Coq.

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