package lrgrep

Syntax error analyser

This repository provides different tools to work on the error messages of a menhir-generated parser.

The main tool is lrgrep. It takes:

• a compiled Menhir grammar (a .cmly file, produced by passing --cmly flag to Menhir)
• a list of rules (usually a .lrgrep file).

If the list of rule is well-formed, it produces an OCaml module that can match the rules against the state of a parser at runtime.

By carefully crafting the rules, one can provide fine-grained message to explain syntax errors.

The repository is is structured as follow:

• the main tool, lrgrep, can be found in src/main.ml
• support implements the compact table representation shared by the generator and the generated analysers via the lrgrep.runtime library
• lib implements various algorithms used by other tools

Getting started with LRGrep codebase

I am trying to document the code. Each of the src, lib, and support directories contain a README.md that briefly explains the purpose of this directory.

External dependencies that are worth knowing:

• MenhirSdk is a part of the Menhir parser generator that allows external tool to post-process compiled grammars
• Cmon is a pretty-printer for recursive values
• Fix is a library for computing fixed points; it also provides a convenient representation of finite sets
• LRijkstra is taken from Menhir and implements the algorithm described in "Faster Reachability Analysis for LR(1) Parsers", though we apply it for a slightly different purpose than the one described in the articles