Scallion is a library for writing parsers and pretty printers for LL(1) languages in Scala.

A comprehensive Scaladoc API is available online.

Scallion uses a novel parsing algorithm that we have described in the PLDI'20 paper: Zippy LL(1) Parsing with Derivatives. The algorithm has been formally proven correct in Coq.

• JSON: This example showcases how to build a basic JSON parser using Scallion.
• Lambda Calculus: This example shows how to get a pretty printer almost for free alongside your parser.
• Calculator: This example shows how to use the operators combinator to easily handle operators with various associativities and priorities.
• Roman Numerals: This example presents a simple parser and pretty printer for roman numerals.