Yacc is dead

TL;DR

This paper introduces two innovative parsing methods for context-free languages, extending derivatives to grammars and parser combinators, resulting in a compact, efficient parsing library suitable for practical use.

Contribution

It presents novel derivative-based parsing techniques for context-free grammars, enabling small, efficient, and easy-to-implement parsers in Scala and Haskell.

Findings

Parsed millions of tokens per second in experiments

The parsing library is less than 250 lines of code

Techniques are practical for real-world applications

Abstract

We present two novel approaches to parsing context-free languages. The first approach is based on an extension of Brzozowski's derivative from regular expressions to context-free grammars. The second approach is based on a generalization of the derivative to parser combinators. The payoff of these techniques is a small (less than 250 lines of code), easy-to-implement parsing library capable of parsing arbitrary context-free grammars into lazy parse forests. Implementations for both Scala and Haskell are provided. Preliminary experiments with S-Expressions parsed millions of tokens per second, which suggests this technique is efficient enough for use in practice.