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Structural Recursive Definitions in Type Theory
 Automata, Languages and Programming, 25th International Colloquium, ICALPâ€™98
, 1998
"... We introduce an extension of the Calculus of Construction with inductive and coinductive types that preserves strong normalisation for a lazy computation relation. This extension considerably enlarges the expressiveness of the language, enabling a direct translation of recursive programs, while kee ..."
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We introduce an extension of the Calculus of Construction with inductive and coinductive types that preserves strong normalisation for a lazy computation relation. This extension considerably enlarges the expressiveness of the language, enabling a direct translation of recursive programs, while keeping a relatively simple collection of typing rules. 1 Introduction The last twenty five years have seen an increasing development of different proof environments based on type theory. Several type theories have been proposed as a foundation of such proof environments [15, 6, 16], trying to find an accurate compromise between two criteria. On the one hand, we search for extensions of type theory that preserve its conceptual simplicity of type theory (a few primitive constructions, a small number of typing rules) and metatheoretical properties ensuring its soundness and a direct mechanisation (strong normalisation, decidability of typechecking, etc). On the other hand, we would like to pro...
Monotone Inductive and Coinductive Constructors of Rank 2
 Proceedings of CSL 2001
, 2001
"... A generalization of positive inductive and coinductive types to monotone inductive and coinductive constructors of rank 1 and rank 2 is described. The motivation is taken from initial algebras and nal coalgebras in a functor category and the CurryHowardcorrespondence. The denition of the system as ..."
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Cited by 10 (4 self)
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A generalization of positive inductive and coinductive types to monotone inductive and coinductive constructors of rank 1 and rank 2 is described. The motivation is taken from initial algebras and nal coalgebras in a functor category and the CurryHowardcorrespondence. The denition of the system as a calculus requires an appropriate denition of monotonicity to overcome subtle problems, most notably to ensure that the (co)inductive constructors introduced via monotonicity of the underlying constructor of rank 2 are also monotone as constructors of rank 1. The problem is solved, strong normalization shown, and the notion proven to be wide enough to cover even highly complex datatypes. 1
Parigot's Second Order λμCalculus and Inductive Types
, 2001
"... . A new proof of strong normalization of Parigot's (second order) calculus is given by a reductionpreserving embedding into system F (second order polymorphic calculus). The main idea is to use the least stable supertype for any type. These nonstrictly positive inductive types and their associat ..."
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Cited by 1 (0 self)
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. A new proof of strong normalization of Parigot's (second order) calculus is given by a reductionpreserving embedding into system F (second order polymorphic calculus). The main idea is to use the least stable supertype for any type. These nonstrictly positive inductive types and their associated iteration principle are available in system F, and allow to give a translation vaguely related to CPS translations (corresponding to the Kolmogorov embedding of classical logic into intuitionistic logic). However, they simulate Parigot's reductions whereas CPS translations hide them. As a major advantage, this embedding does not use the idea of reducing stability (:: ! ) to that for atomic formulae. Therefore, it even extends to noninterleaving positive xedpoint types. As a nontrivial application, strong normalization of calculus, extended by primitive recursion on monotone inductive types, is established. 1 Introduction calculus [12] essentially is the extension of nat...