Efficient Mendler-Style Lambda-Encodings in Cedille

Efficient lambda encodings for Mendler-style coinductive types in Cedille

In the calculus of dependent lambda eliminations (CDLE), it is possible to define inductive datatypes via lambda encodings that feature constant-time destructors and a course-of-values induction scheme. This paper begins to address the missing derivations for the dual, coinductive types. Our derivation utilizes new methods within CDLE, as there are seemingly fundamental difficulties in adapting previous known approaches for deriving inductive types. The lambda encodings we present implementing coinductive types feature constant-time constructors and a course-of-values corecursion scheme. Coind…

Simulating Large Eliminations in Cedille

Large eliminations provide an expressive mechanism for arity- and type-generic programming. However, as large eliminations are closely tied to a type theory's primitive notion of inductive type, this expressivity is not expected within polymorphic lambda calculi in which datatypes are encoded using impredicative quantification. We report progress on simulating large eliminations for datatype encodings in one such type theory, the calculus of dependent lambda eliminations (CDLE). Specifically, we show that the expected computation rules for large eliminations, expressed using a derived type of …

Elaborating Inductive Definitions and Course-of-Values Induction in Cedille

In the Calculus of Dependent Lambda Eliminations (CDLE), a pure Curry-style type theory, it is possible to generically λ-encode inductive datatypes which support course-of-values (CoV) induction. We present a datatype subsystem for Cedille (an implementation of CDLE) that provides this feature to programmers through convenient notation for declaring datatypes and for defining functions over them by case analysis and fixpoint-style recursion guarded by a type-based termination checker. We demonstrate that this does not require extending CDLE by showing how datatypes and functions over them elab…

Cedille 中的单调递归类型与递归数据表示

Monotone recursive types and recursive data representations in Cedille

本文在 Cedille 中基于 Tarski 不动点定理推导单调递归类型，并应用于 Parigot 和 Scott 编码，证明归纳性质并给出高效唯一的迭代与原始递归方案。

A Weakly Initial Algebra for Higher-Order Abstract Syntax in Cedille

Cedille is a relatively recent tool based on a Curry-style pure type theory, without a primitive datatype system. Using novel techniques based on dependent intersection types, inductive datatypes with their induction principles are derived. One benefit of this approach is that it allows exploration of new or advanced forms of inductive datatypes. This paper reports work in progress on one such form, namely higher-order abstract syntax (HOAS). We consider the nature of HOAS in the setting of pure type theory, comparing with the traditional concept of environment models for lambda calculus. We s…