GBNF

A library for parsing .gbnf grammar files in Javascript.

Install

``bash
npm install gbnf
`

Usage

Pass your grammar to GBNF:

`javascript
import GBNF from 'gbnf';
const state = GBNF(
root ::= "yes" | "no"
)
`

If the grammar is invalid, GBNF will throw.

GBNF returns a state representing the parsed state:

`javascript
import GBNF from 'gbnf';
const state = GBNF(
root ::= "yes" | "no"
)
for (const rule of state) {
console.log(rule);
// { type: "CHAR", value: ["y".charCodeAt(0)]}
// { type: "CHAR", value: ["n".charCodeAt(0)]}
}
`

state can be iterated over. (You can also call the iterator method directly with state.rules()). state cannot be indexed directly, but can easily be cast to an array with [...state] and indexed that way.

States are _immutable_. To parse a new token, call state.add():

`javascript
import GBNF from 'gbnf';
let state = GBNF(
root ::= "I like green eggs and ham"
)
console.log([...state]); // [{ type: "CHAR", value: ["I".charCodeAt(0)]}]
state = state.add("I li");
console.log([...state]); // [{ type: "CHAR", value: ["k".charCodeAt(0)]}]
state = state.add("ke gree");
console.log([...state]); // [{ type: "CHAR", value: ["n".charCodeAt(0)]}]
`

The possible rules returned include:

- CHAR - contains an array of either numbers representing code points to match, _or_ an array of two numbers denoting a range within which a code point may appear.
- CHAR_EXCLUDED - contains an array of numbers representing code points _not_ to match, _or_ an array of two numbers denoting a range within which a code point may _not_ appear.
- END` - denotes a valid end of a string.