Abstract. We propose a new language for writing programs with dependent types which can be elaborated into partial Coq terms. This language permits to establish a phase distinction between writing and proving algorithms in the Coq environment. Concretely, this means allowing to write algorithms as easily as in a practical functional programming language whilst giving them as rich a specification as desired and proving that the code meets the specification using the whole Coq proof apparatus. This is achieved by extending conversion to an equivalence which relates types and subsets based on them, a technique originating from the “Predicate subtyping ” feature of PVS and following mathematical convention. The typing judgements can be translated to the Calculus of (Co-)Inductive Constructions (Cic) by means of an interpretation which inserts coercions at the appropriate places. These coercions can contain existential variables representing the propositional parts of the final term, corresponding to proof obligations (or PVS type-checking conditions). A prototype implementation of this process is integrated with the Coq environment. 1

Abstract. In this paper, we show how Miquel’s Implicit Calculus of Constructions (ICC) can be used as a programming language featuring dependent types. Since this system has an undecidable type-checking, we introduce a more verbose variant, called ICC ∗ which fixes this issue. Datatypes and program specifications are enriched with logical assertions (such as preconditions, postconditions, invariants) and programs are decorated with proofs of those assertions. The point of using ICC ∗ rather than the Calculus of Constructions (the core formalism of the Coq proof assistant) is that all of the static information (types and proof objects) is transparent, in the sense that it does not affect the computational behavior. This is concretized by a built-in extraction procedure that removes this static information. We also illustrate the main features of ICC ∗ on classical examples of dependently typed programs. 1

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As programming languages become more complex, there is a growing call in the research community for machine-checked proofs about programming languages. A key obstacle to this goal is in formalizing name binding, where a new name is created in a limited scope. Name binding is used in almost every programming language to refer to the formal arguments to a function. For example, the function f (x) = x ∗ 2, which doubles its argument, binds the name x for its formal argument. Though this concept is intuitively straightforward, it is complex to define precisely because of the intended properties of name binding. For example, the above function is considered “syntactically equivalent ” to f (y) = y ∗ 2. It is the goal of this dissertation to posit a new technique for encoding name binding, called Higher-Order Encodings with Constructors or HOEC. HOEC encodes name binding with a construct called the ν-abstraction, which binds new constructors in a limited scope. These constructors can then be used to encode names. ν-abstractions already have the required properties of name bindings, so name binding need only be ii formalized once, in the definition of the ν-abstraction. The user thus then gets name

Abstract. We consider the Calculus of Constructions with typed beta-eta equality and an algorithm which computes long normal forms. The normalization algorithm evaluates terms into a semantic domain, and reifies the values back to terms in normal form. To show termination, we interpret types as partial equivalence relations between values and type constructors as operators on PERs. This models also yields consistency of the beta-eta-Calculus of Constructions. The model construction can be carried out directly in impredicative type theory, enabling a formalization in Coq. 1

Abstract. This paper reports on ongoing work on the project of representing the Kenzo system [15] in type theory [11].