Pears - A parser combinator library for Gleam

🚧️ This library is in early development. Expect breaking changes. 🚧

Installation

gleam add pears

Usage

import pears.{type Parser, Parsed}
import pears/chars.{type Char, number}
import pears/combinators.{alt, between, just, lazy, map, sep_by0}

pub type Tree(a) {
  Leaf(a)
  Node(List(Tree(a)))
}

fn tree_parser(p: Parser(Char, a)) -> Parser(Char, Tree(a)) {
  let tree = lazy(fn() { tree_parser(p) })
  let leaf = map(p, Leaf)
  let node =
    tree
    |> sep_by0(just(","))
    |> between(just("["), just("]"))
    |> map(Node)
  alt(leaf, node)
}

pub fn main() {
  let parse_result =
    "[1,[2,3],4]"
    |> chars.input()
    |> tree_parser(number())

  let assert Ok(Parsed([], Node([Leaf(1), Node([Leaf(2), Leaf(3)]), Leaf(4)]))) =
    parse_result
}

Further documentation can be found at https://hexdocs.pm/pears.

See the test directory for more examples.

What’s missing?

• Proper error handling
• Test helpers
• …

Development

gleam test  # Run the tests
gleam shell # Run an Erlang shell