HKU PL Group

We are a group of programming language researchers who study topics about functional language design, type theory, compilers and program analysis.
The University of Hong Kong

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Disjoint Intersection Types

Calculi about disjoint intersection types enable an highly modular and compositional programming style that addresses the Expression Problem naturally, and allows for a much more dynamic form of inheritance.

Compositional Programming

Those works present a novel modular programming style.

Gradual Typing

This work presents a generalized definition of consistent subtyping that works for polymorphic types.

Dependent Types

Those works propose a unified syntax that accounts for types and terms which still preserves decidable type-checking.

Higher-Ranked Polymorphism

This paper provides the first mechanized formalization of type inference for higher-ranked polymorphism.

Kind Inference

This work proposes a solution of challenge of kind inference for datatype declarations for Haskell98 and modern Haskell.

Subtyping for Iso-recursive Types

A new iso-recursive subtyping formulation which takes advantage over other designs on both theoretical side and implementation side.

Bi-directional Type Checking

This paper presents a variant of bi-directional type checking where the type information flows from arguments to functions.

Intersection and Union Types

This paper proposes a novel methodology for designing subtyping relations that exploits duality between intersection types and union types.

Type-directed Operational Semantics

Type-directed operational semantics(TDOS) is a variant of small-step operational semantics. In TDOS, type annotations become operationally relevant and can affect the result of a program.

Seminar

  • Revisiting type disjointness
    Jul 27, 2021
    In this problem session, we will go over the existing definitions of type disjointness and discuss an alternative approach proposed by Jimmy.

  • Applicative Intersection Types
    Jul 6, 2021
    λi adopts a classical bidirectional type checking and gives rise to many type annotations in the process of function application. In this seminar talk, I will give an introduction to...

  • Type-Directed Operational Semantics for Gradual Typing
    Jun 22, 2021
    The semantics of gradually typed languages is typically given indirectly via an elaboration into a cast calculus. This contrasts with more conventional formulations of programming language semantics, where the semantics...

  • A Dependently Typed Calculus with Polymorphic Subtyping
    Jun 22, 2021
    A polymorphic subtyping relation, which relates more general types to more specific ones, is at the core of many modern functional languages. As those languages start moving towards dependently typed...

  • Revisiting Iso-recrusive Subtyping
    May 25, 2021
    The Amber rules are well-known and widely used for subtyping iso-recursive types. They were first briefly and informally introduced in 1985 by Cardelli in a manuscript describing the Amber language....

Gallery

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    Lab dinner 2019