GrammKit

GrammKit is a tool for generating syntax diagrams (also known as railroad diagrams) for parser grammars. Check out the online version.

Currently these grammar formats are supported:

• PEG.js - it is parsed into internal AST of PEG.js which is then translated using peg-rd.js.
• EBNF defined in W3C standards - it parsed into AST using parse-ebnf.pegjs
• Ohm - translation is done using semantic actions in ohm-rd.js

Is uses the railroad-diagrams library to generate SVG images.

Use the command line utility

npm install -g grammkit

To generate static html page run grammkit yourgrammar.peg.

To generate markdown file run grammkit -t md yourgrammar.peg. This will generate separate SVG files and a markdown file that includes them.

Use the library

npm install grammkit

var grammkit = require('grammkit');
var parse = require('pegjs/lib/parser').parse;

var grammar = parse('start = left ("+" / "-") right');
grammkit.diagram(grammar.rules[0]);
// => '<svg>...</svg>'

The SVG renders as:

Development

Clone repo and install dependencies with npm install.

Run npm run dev and open browser at http://localhost:1234 .

Here is an overview how the format conversion works:

Changelog

v0.7.1

• Bumped up dependencies to make npm audit happy (#20)
• Removed references to rawgit.com since it shut down (#21)

v0.7.0

• Fixed compatibility with latest version of pegjs (v0.10.0)

v0.6.3

• Fix onclick events for SVG elements (#13)

v0.6.2

• Bump dependencies to satisfy npm audit

v0.6.1

• Update ohm dependency

v0.6.0

• Add support for ohm grammars
• Choose different formats in web app and cli

Related projects

List of other project worth checking out.

• Jison debugger - interesting visualization of a parse tree for jison grammars
• Ohm interactive editor - online editor for ohm grammars that also visualizes parse tree
• AST Explorer
• Godbolt Compiler Explorer