Cypress

A parser library inspired by a scaled down derivative of the FParsec combinator library in F#.

I was also inspired by chumsky a very elegant parser combinator library which I have enjoyed using!

The goal of this project was to develop a simple parser combinator library with which people can write and parse expressive languages with ease. It is still a work in progress and there are areas that still need to be cleaned up but I believe that I have achieved my goal.

Features

• Expressive combinators
• Labelling parser for easier debugging
• Generic over input and output
• Macros for ergonomic parsing for common tasks

Example

I have populated /examples with a parser of certain simple languages, along with an evaluator for a select few, to show using this library by example. I hope to populate one or two more sophisticated implementations soon. Below is a simple parser for BrainFuck which seems to be the go to simple language parser that libraries refer to, so here it is.

use cypress::prelude::*;

#[derive(Debug, Clone, PartialEq)]
enum Instruction {
    Left,
    Right,
    Increment,
    Decrement,
    Read,
    Write,
    Loop(Vec<Self>),
}

fn bf_parser<'a>() -> impl Parser<'a, u8, Vec<Instruction>> {
    recursive(|expr| {
        let instr = choice!(
            select! {
                '<' => Instruction::Left
                '>' => Instruction::Right
                '+' => Instruction::Increment
                '-' => Instruction::Decrement
                ',' => Instruction::Read
                '.' => Instruction::Write
            }
            expr.many()
                .between(just('['), just(']'))
                .map(Instruction::Loop)
        );

        Box::new(instr)
    })
    .many()
    .until_end()
}

let input = b"+++++[>>+<<-]".into_input();

// parse bf input
bf_parser.parse(input);

Note

This is my first published project so if you have thoughts please feel free to open an issue or a PR with ideas and fixes!

License

cypress is licensed under the BSD 3 license (see LICENSE in the main repository).