https://github.com/kseo/untyped

An implementation of untyped lambda calculus in Haskell
https://github.com/kseo/untyped

Last synced: about 2 months ago
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An implementation of untyped lambda calculus in Haskell

• Host: GitHub
• URL: https://github.com/kseo/untyped
• Owner: kseo
• License: bsd-3-clause
• Created: 2016-12-06T11:16:02.000Z (about 8 years ago)
• Default Branch: master
• Last Pushed: 2016-12-24T16:12:11.000Z (about 8 years ago)
• Last Synced: 2024-10-11T23:22:19.589Z (3 months ago)
• Language: Haskell
• Size: 19.5 KB
• Stars: 6
• Watchers: 3
• Forks: 3
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
untyped

=======

An implementation of untyped lambda calculus in Haskell

# Overview

`untyped` is an implementation of untyped lambda calculus presented by Benjamin C. Pierce in his [Types and Programming Languages][tapl]. I transliterated the original source code written in OCaml into Haskell except for the parser which I rewrote in [Parsec][parsec].

# Syntax

* Variables: `x`

* Applications: `x x`

* Lambda abstractions: `\x.x`

# Implementation Details

* The representation of a variable is a number - its De Brujin index

* Evaluation performs substitution

* Pretty printer removes redundant parenthesis

# REPL

`untypedi` is a REPL where you can input a lambda calculus term.

```

% (\x.x) (\x.x)

\x.x

% (\x.y)

Invalid lambda caluclus: (\x.y)

```

[parsec]: https://hackage.haskell.org/package/parsec

[tapl]: https://www.google.co.kr/search?q=tapl&oq=tapl&aqs=chrome..69i57j69i60l3j0l2.776j0j7&sourceid=chrome&ie=UTF-8#q=tapl+benjamin