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It is possible to represent the terms of a syntax with binding constructors by a family of types, indexed by the free variables that may occur. This approach has been used several times for the study of syntax and substitution, but never for the formalization of the metatheory of a typing system. We describe a recent formalization of the metatheory of Pure Type Systems in Coq as an example of such...
The prototype of a content based search engine for mathematical knowledge supporting a small set of queries requiring matching and/or typing operations is described. The prototype — called Whelp — exploits a metadata approach for indexing the information that looks far more flexible than traditional indexing techniques for structured expressions like substitution, discrimination, or context trees...
Most approaches to the formal analysis of cryptography protocols make the perfect cryptographic assumption, which entails for example that there is no way to obtain knowledge about the plaintext pertaining to a ciphertext without knowing the key. Ideally, one would prefer to abandon the perfect cryptography hypothesis and reason about the computational cost of breaking a cryptographic scheme by achieving...
We present a formalization of a constructive proof of weak normalization for the simply-typed λ-calculus in the theorem prover Isabelle/HOL, and show how a program can be extracted from it. Unlike many other proofs of weak normalization based on Tait’s strong computability predicates, which require a logic supporting strong eliminations and can give rise to dependent types in the extracted program,...
This paper reports on the correctness proof of compiler optimizations based on data-flow analysis. We formulate the optimizations and analyses as instances of a general framework for data-flow analyses and transformations, and prove that the optimizations preserve the behavior of the compiled programs. This development is a part of a larger effort of certifying an optimizing compiler by proving semantic...
We discuss two complete formalisations of bitonic sort in constructive type theory. Bitonic sort is one of the fastest sorting algorithms where the sequence of comparisons is not data-dependent. In addition, it is a general recursive algorithm. In the formalisation we face two main problems: only structural recursion is allowed in type theory, and a formal proof of the correctness of the algorithm...
We propose a simple theory of monotone functions that is the basis for the implementation of a tactic that generalises one step conditional rewriting by “propagating” constraints of the form xRy where the relation R can be weaker than an equivalence relation. The constraints can be propagated only in goals whose conclusion is a syntactic composition of n-ary functions that are...
We give a formal model for a first order functional language to be executed on a stack machine and for a bytecode verifier that performs two kinds of static verifications : a type analysis and a shape analysis, that are part of a system used to ensure resource bounds. Both are instances of a general data flow analyzer due to Kildall. The generic algorithm and both of its instances are certified with...
In the paper we show, based on two problems in general topology (Kuratowski closure-complement and Isomichi’s classification of condensed subsets), how typed objects can be used instead of untyped text to better represent mathematical content understandable both for human and computer checker. We present mechanism of attributes and clusters reimplemented in Mizar fairly recently to fit authors’ expectations...
We present a tool for automated theorem proving in Agda, an implementation of Martin-Löf’s intuitionistic type theory. The tool is intended to facilitate interactive proving by relieving the user from filling in simple but tedious parts of a proof. The proof search is conducted directly in type theory and produces proof terms. Any proof term is verified by the Agda type-checker, which ensures soundness...
Surreal Numbers form a totally ordered (commutative) Field, containing copies of the reals and (all) the ordinals. I have encoded most of the Ring structure of surreal numbers in Coq. This encoding relies on Aczel’s encoding of set theory in type theory. This paper discusses in particular the definitional or proving points where I had to diverge from Conway’s or the most natural way, like separation...
We present four constructions for standard equipment which can be generated for every inductive datatype: case analysis, structural recursion, no confusion, acyclicity. Our constructions follow a two-level approach—they require less work than the standard techniques which inspired them [11,8]. Moreover, given a suitably heterogeneous notion of equality, they extend without difficulty to inductive...
Within a framework of correct code-generation from HOL-specifications, we present a particular instance concerned with the optimized compilation of a lazy language (called MiniHaskell) to a strict language (called MiniML). Both languages are defined as shallow embeddings into denotational semantics based on Scott’s cpo’s, leading to a derivation of the corresponding operational semantics in...
Peter Hancock and Anton Setzer developed the notion of interface to introduce interactive programming into dependent type theory. We generalise their notion and get an even simpler definition for interfaces. With this definition the relationship of interfaces to games becomes apparent. In fact from a game theoretical point of view interfaces are nothing other than special games. Programs are strategies...
We introduce a pure type system (PTS) λZ with four sorts and show that this PTS captures the proof-theoretic strength of Zermelo’s set theory. For that, we show that the embedding of the language of set theory into λZ via the ‘sets as pointed graphs’ translation makes λZ a conservative extension of IZ+AFA+TC (intuitionistic Zermelo’s set theory plus Aczel’s antifoundation axiom plus the axiom of transitive...
In this paper we use the Epigram language to define the universe of regular tree types—closed under empty, unit, sum, product and least fixpoint. We then present a generic decision procedure for Epigram’s in-built equality at each type, taking a complementary approach to that of Benke, Dybjer and Jansson [7]. We also give a generic definition of map, taking our inspiration from Jansson and Jeuring...
Baaz and Fermueller gave in 2003 an original characterization of constructive existence in classical logic [2]. In this note, we give a simple proof of this result based on cut-elimination in sequent calculus. The interest of this proof besides its simplicity is that it allows in particular to generalize the result to other logics enjoying cut-elimination. We also briefly discuss the significance...
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