https://github.com/notJoon/lambda

λ-calculus parser made by rust
https://github.com/notJoon/lambda

json lambda-calculus parser rust

Last synced: about 2 months ago
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λ-calculus parser made by rust

• Host: GitHub
• URL: https://github.com/notJoon/lambda
• Owner: notJoon
• Created: 2023-04-12T04:48:14.000Z (about 1 year ago)
• Default Branch: main
• Last Pushed: 2023-04-21T03:47:44.000Z (about 1 year ago)
• Last Synced: 2024-02-05T02:48:35.981Z (5 months ago)
• Topics: json, lambda-calculus, parser, rust
• Language: Rust
• Homepage:
• Size: 17.6 KB
• Stars: 4
• Watchers: 1
• Forks: 0
• Open Issues: 2
• Metadata Files:
  • Readme: README.md

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• awesome-rust-formalized-reasoning - Lambda Calculus Parser - λ-calculus parser. (Projects / Libraries)

README

        
# Lambda Calculus Parser

This is a parser for **λ-calculus** expressions. It takes a  λ-terms as input, parses it and returns a JSON representation of the term. The parser currently supports  λ-abstractions, variables and function applications. It uses a recursive descent parsing technique.

## Features

- Parses λ-abstractions, variables and function applications

- Returns a JSON representation of the parsed λ-term

- Includes a REPL for interactive parsing

## Usage

The parser is implemented as a **`Parser`** struct with several methods. It uses a `Peekable` iterator to read the input string single characters at a time. The main parsing function, `parse_term`, loop over the input string and determine the appropriate parsing function to call based on the current character.

The parsing functions are:

- `parse_lambda` : Parsed a λ-abstraction(e.g., `λx.x`)

- `parse_application` : Parses a function application (e.g., `(f x)`)

- `parse_variable` : Parses a variable (e.g., `x`)

The parser returns an enum **`Term`**, which can be one of the following:

- `Lambda`: Represents a λ-abstraction with a binding variable and a body

- `Application`: Represents a function application with a function and an argument

- `Variable`: Represents a variable with a name

- `Null`: Represents an empty term or failed parsing

The parsed `Term` is then converted to a JSON format using the `term_to_json` function. which converts the `Term` to a `serde_json::Value` object.

## Example

Here's an example of how to parse a λ-term using the parser:

```rust

fn main() {

    let input = "λf. λx. (f x)";

    let term = parse(input);

    let json = term_to_json(&term);

    println!("{}", serde_json::to_string_pretty(&json).unwrap());

}

```

This will output:

```json

{

  "bind": "f",

  "body": {

    "bind": "x",

    "body": {

      "arg": {

        "name": "x",

        "tag": "var"

      },

      "func": {

        "name": "f",

        "tag": "var"

      },

      "tag": "application"

    },

    "tag": "lambda"

  },

  "tag": "lambda"

}

```

> **Note:** There is a problem that the position of the tag goes down when print the current JSON. This will be fixed in the future.

To use the REPL, run the following command:

```bash

cargo run

```

After that, you can enter a λ-term and press enter to parse it. The REPL will print the parsed JSON representation of the term.