nearley-moo

moo (ultra-fast tokenizer) plugin for nearley :cow2:

install

with npm

1npm install nearley-moo --save

with yarn

1yarn add nearley-moo

usage

index.js

1const moo = require('moo')
2const nearley = require('nearley')
3const grammar = require('./grammar.js') // compiled from grammar.ne
4const tokens = require('./tokens.js')
5
6const nm = require('nearley-moo').parser(nearley, grammar) // curried
7
8let parser = nm(moo.compile(tokens))
9
10// ignored tokens will not be passed to nearley
11// helpful for whitespace and/or comments
12parser.ignore('whitespace') // may be Array<string> or String
13
14// feed your lexer+parser combo as normal
15parser.feed('if true then moomoomoo else cows')
16
17console.log(parser.results) // just like nearley

tokens.js

1module.exports = {
2  whitespace: /[ \t]+/,
3  moo: /(moo)+/,
4  cows: /cows/,
5  boolean: [ 'true', 'false' ],
6  keyword: [ 'if', 'then', 'else'],
7}

grammar.ne

1@{%
2
3const nm = require('nearley-moo')
4const tokens = require('./tokens.js')
5
6nm(tokens)
7
8%}
9
10main -> %keyword_if expression %keyword_then expression %keyword_else expression
11
12expression -> boolean
13            | %moo
14            | %cows
15
16boolean -> %boolean_true  {% d => true %}
17         | %boolean_false {% d => false %}