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A LargeScale Experiment in Executing Extracted Programs
"... It is a wellknown fact that algorithms are often hidden inside mathematical proofs. If these proofs are formalized inside a proof assistant, then a mechanism called extraction can generate the corresponding programs automatically. Previous work has focused on the difficulties in obtaining a program ..."
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It is a wellknown fact that algorithms are often hidden inside mathematical proofs. If these proofs are formalized inside a proof assistant, then a mechanism called extraction can generate the corresponding programs automatically. Previous work has focused on the difficulties in obtaining a program from a formalization of the Fundamental Theorem of Algebra inside the Coq proof assistant. In theory, this program allows one to compute approximations of roots of polynomials. However, as we show in this work, there is currently a big gap between theory and practice. We study the complexity of the extracted program and analyze the reasons of its inefficiency, showing that this is a direct consequence of the approach used throughout the formalization.
A ProofTheoretic Approach to Hierarchical Math Library Organization
, 2005
"... The relationship between theorems and lemmas in mathematical reasoning is often vague. No system exists that formalizes the structure of theorems in a mathematical library. Nevertheless, the decisions we make in creating lemmas provide an inherent hierarchical structure to the statements we prove. I ..."
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The relationship between theorems and lemmas in mathematical reasoning is often vague. No system exists that formalizes the structure of theorems in a mathematical library. Nevertheless, the decisions we make in creating lemmas provide an inherent hierarchical structure to the statements we prove. In this paper, we develop a formal system that organizes theorems based on scope. Lemmas are simply theorems with a local scope. We develop a representation of proofs that captures scope and present a set of proof rules to create and reorganize the scopes of theorems and lemmas. The representation and rules allow systems for formalized mathematics to more accurately reflect the natural structure of mathematical knowledge.
λµPRL – A Proof Refinement Calculus for Classical Reasoning
 in Computational Type Theory Diploma thesis, Institut für Informatik, Universität Potsdam
, 2009
"... Abstract. We present a hybrid proof calculus λµPRL that combines the propositional fragment of computational type theory with classical reasoning rules from the λµcalculi. The calculus supports the topdown development of proofs as well as the extraction of proof terms in a functional programming l ..."
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Abstract. We present a hybrid proof calculus λµPRL that combines the propositional fragment of computational type theory with classical reasoning rules from the λµcalculi. The calculus supports the topdown development of proofs as well as the extraction of proof terms in a functional programming language extended by a nonconstructive binding operator. It enables a user to employ a mix of constructive and classical reasoning techniques and to extract algorithms from proofs of specification theorems that are fully executable if classical arguments occur only in proof parts related to the validation of the algorithm. We prove the calculus sound and complete for classical propositional logic, introduce the concept of µsafe terms to identify proof terms corresponding to constructive proofs and show that the restriction of λµPRL to µsafe proof terms is sound and complete for intuitionistic propositional logic. We also show that an extension of λµPRL to arithmetical and firstorder expressions is isomorphic to Murthy’s calculus P ROGK.
RESTRUCTURING FORMAL MATHEMATICS FOR NATURAL TEXTS
, 2004
"... In the presence of growing collections of formal mathematics, and renewed interest in formal mathematics and automated theorem proving for new domains such as hardware or code verification, it is vital to be able to present formal content accessibly to broad audiences. We propose a novel approach to ..."
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In the presence of growing collections of formal mathematics, and renewed interest in formal mathematics and automated theorem proving for new domains such as hardware or code verification, it is vital to be able to present formal content accessibly to broad audiences. We propose a novel approach to constructing a content planner for formal mathematics produced by a tacticstyle prover which capitalizes on the inherent structure of the formal proofs. Though it had been posited that highlevel formal structure is unsuitable as a source of information for text generation, due to its heuristic nature and necessary lack of details, we are able to show that this is not the case. Tacticstyle proofs share significant structural commonality with the discourse structure of corresponding texts. These commonalities allow a content planner to be constructed which need only use lowlevel logical content as a supplementary information source to the generation process. To show that this is the case, we collected two corpora of texts generated to communicate the proof content of a series of formal proofs produced by the Nuprl