https://github.com/tomprimozic/type-systems

Implementations of various type systems in OCaml.
https://github.com/tomprimozic/type-systems

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Implementations of various type systems in OCaml.

• Host: GitHub
• URL: https://github.com/tomprimozic/type-systems
• Owner: tomprimozic
• License: unlicense
• Created: 2014-01-30T00:17:18.000Z (over 10 years ago)
• Default Branch: master
• Last Pushed: 2015-08-31T06:47:52.000Z (about 9 years ago)
• Last Synced: 2024-05-12T12:37:25.981Z (4 months ago)
• Language: OCaml
• Size: 440 KB
• Stars: 1,515
• Watchers: 57
• Forks: 73
• Open Issues: 8
• Metadata Files:
  • Readme: README.md

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• awesome-list - type-systems

README

        
Grow Your Own Type System

=========================

This repository contains implementations of different type systems in OCaml.

It is meant to help out anyone who wants to learn more about advanced type systems and

type inference or experiment by extending or implementing their own. The implementations

are minimal and contain code that is (hopefully) simple and clear.

-   [**algorithm_w**](https://github.com/tomprimozic/type-systems/tree/master/algorithm_w)

    contains one of the most basic yet efficient implementation of Damas-Hindley-Milner

    type inference algorithm (used in functional languages such as OCaml, Haskell and Elm)

    called *Algorithm W*. Uses references to simulate type substitutions and assigns

    ranks/levels to type variables to simplify let-generalization.

-   [**extensible_rows**](https://github.com/tomprimozic/type-systems/tree/master/extensible_rows)

    extends **algorithm_w** with type inference for extensible records/rows

    with scoped labels, based on Daan Leijen's excellent [paper][extensible_rows]. Although

    this is just one way of implementing extensible records, it's extremly simple and

    surprisingly useful, and was incorporated into the programming language

    [Elm](http://elm-lang.org/learn/Records.elm).

-   [**extensible_rows2**](https://github.com/tomprimozic/type-systems/tree/master/extensible_rows2)

    is an optimized implementation of **extensible_rows**.

-   [**first_class_polymorphism**](https://github.com/tomprimozic/type-systems/tree/master/first_class_polymorphism)

    extends **algorithm_w** with type checking and partial type inference for first-class

    and higher-rank polymorphism, based on another one of Daan Leijen's [papers][hmf].

    This system requires slightly more type annotations than other attempts at type inference for

    first-class polymorphism, such as MLF, but is considerably simpler to implements

    and use.

-   [**gradual_typing**](https://github.com/tomprimozic/type-systems/tree/master/gradual_typing)

    is another simple extension of **algorithm_w** based on a [paper][gradual] by Jeremy G. Siek

    and Manish Vachharajani. Gradual typing combines the benefits of static and dynamic typing,

    allowing programmers to make dynamic programs safer by adding static type information, and

    make static programs more flexible by delaying type-checking until runtime when necessary.

-   [**refined_types**](https://github.com/tomprimozic/type-systems/tree/master/refined_types)

    is an experiment that extends the HM type system with dependent types in the form of function

    contracts. It uses an external automatic theorem prover to verify that function contracts are

    satisfied, to prevent many of the most common software errors, such

    as division by zero and out-of-bounds array access.

[extensible_rows]: http://research.microsoft.com/apps/pubs/default.aspx?id=65409

[hmf]: http://research.microsoft.com/apps/pubs/default.aspx?id=132621

[gradual]: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.84.8219&rep=rep1&type=pdf