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arXiv 1611.09263cs.LOmath.CTmath.LO
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守护立方类型论

Guarded Cubical Type Theory

Lars Birkedal, Aleš Bizjak, Ranald Clouston, Hans Bugge Grathwohl, Bas Spitters, Andrea Vezzosi

摘要:

本文将保护依赖类型论(GDTT)与立方类型论(CTT)相结合,改进了GDTT中等式的处理. GDTT是一种具有保护递归类型的可拓类型论,它对于建立程序逻辑模型以及使用共归纳类型进行程序设计和推理是有用的。我们希望用可判定的类型检查实现GDTT,同时仍然支持非平凡的等式证明,这些证明是关于保护递归构造的扩展的原因。CTT是Martin-Löf类型论的变体,其中单位类型被项之间的抽象路径所取代。CTT提供了一个计算解释的功能扩展性,享有规范的自然数类型,并被构造为支持可判定的类型检查。我们的新类型论,守护立方类型论(GCTT),提供了一个计算解释的可拓性守护递归类型。这进一步扩展了CTT作为数学和计算机科学形式化基础的基础。我们提出的例子来证明我们的类型论,所有这些都已检查使用原型类型检查器实现的表达能力。我们表明,CTT可以给出语义的立方体范畴和一个小的类别与初始对象的产品上的预层。然后,我们表明,类别的立方体类别和欧米茄的产品上的预层提供GCTT的语义。

英文摘要:

This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of program logics, and for programming and reasoning with coinductive types. We wish to implement GDTT with decidable type checking, while still supporting non-trivial equality proofs that reason about the extensions of guarded recursive constructions. CTT is a variation of Martin-Löf type theory in which the identity type is replaced by abstract paths between terms. CTT provides a computational interpretation of functional extensionality, enjoys canonicity for the natural numbers type, and is conjectured to support decidable type-checking. Our new type theory, guarded cubical type theory (GCTT), provides a computational interpretation of extensionality for guarded recursive types. This further expands the foundations of CTT as a basis for formalisation in mathematics and computer science. We present examples to demonstrate the expressivity of our type theory, all of which have been checked using a prototype type-checker implementation. We show that CTT can be given semantics in presheaves on the product of the cube category and a small category with an initial object. We then show that the category of presheaves on the product of the cube category and omega provides semantics for GCTT.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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