https://github.com/takamin/lex-bnf

General-purpose recursive descent parser and evaluator
https://github.com/takamin/lex-bnf

analyzer bnf bnf-parser javascript lex-bnf lexical-analysis npm parser-generator

Last synced: about 2 months ago
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General-purpose recursive descent parser and evaluator

• Host: GitHub
• URL: https://github.com/takamin/lex-bnf
• Owner: takamin
• License: mit
• Created: 2018-07-04T11:39:29.000Z (over 6 years ago)
• Default Branch: master
• Last Pushed: 2024-09-28T05:59:16.000Z (3 months ago)
• Last Synced: 2024-10-16T12:03:11.863Z (2 months ago)
• Topics: analyzer, bnf, bnf-parser, javascript, lex-bnf, lexical-analysis, npm, parser-generator
• Language: JavaScript
• Homepage:
• Size: 1.45 MB
• Stars: 8
• Watchers: 2
• Forks: 4
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
Lex-BNF

=======

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This is a **general-purpose recursive descent parser and evaluator**.

Using this module, You can:

1. Defines a syntax rule such as programming languages, expressions, or structured statements.

1. Parses the code written based on the rules.

1. Evaluates the result of the parsing.

__NOTE: The class `BNF` exported in v0.3.3 is deprecated and it can be used as `Language.BNF`.__

Create A `Language` Definition

----

The parser is defined as an instance of `Language` class by using objects of BNF-like

notation and its evaluator functions. Those can run in dynamically and immediately.

The `Language` constructor takes one array of syntax rule.

To create the syntax rule, use `Language.syntax()` function.

__Paramters of `Language.syntax()`:__

1. A name of the syntax rule.

1. An array of a rule which is an array of terms.

    * A character '*' at the end of a rule name as an element of the terms is __Repetition Specifier__ that means the rule is repeatable.

    * See the rule declaration part of `additive-expression` in [sample/calc.js](https://github.com/takamin/lex-bnf/blob/master/sample/calc.js) to use the feature.

1. An evaluator function (optional). It can be omitted when the second parameter contains only one rule which containing only one other name of syntax rule.

Demo: Evaluating arithmetic expression

----

With following files, those shows how define a syntax of language.

* [sample/eval-expr.js](https://github.com/takamin/lex-bnf/blob/master/sample/eval-expr.js)  

A simple calculator script to parse and evaluate an expression from CLI.

* [sample/calc.js](https://github.com/takamin/lex-bnf/blob/master/sample/calc.js)  

An implementation of the calculator syntax.

__run on bash__

```bash

$ node sample/eval-expr.js '(1 + 2) * ((3 + 4) / 2)'

10.5

$

```

Documents

----

* [GitHub Pages](https://takamin.github.io/lex-bnf/)

* API Reference

    * [v1.1.1](https://takamin.github.io/lex-bnf/docs/lex-bnf/1.1.1/)

        * Fix the issue [#16](https://github.com/takamin/lex-bnf/issues/16)

    * [v1.1.0](https://takamin.github.io/lex-bnf/docs/lex-bnf/1.1.0/)

        * Repetition specifier `*` is available for the rule name. It is important for getting correct answer of multi term arithmetic expressions such as `1 - 2 - 3 = ?`.

    * [v1.0.1](https://takamin.github.io/lex-bnf/docs/lex-bnf/1.0.1/)

    * [v1.0.0](https://takamin.github.io/lex-bnf/docs/lex-bnf/1.0.0/)

LICENSE

-------

This software is released under the MIT License, see [LICENSE](LICENSE)