lex-bnf

Lex-BNF
=======

!version
!license

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

* sample/eval-expr.js
A simple calculator script to parse and evaluate an expression from CLI.
* 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
* API Reference
* v1.1.1
* Fix the issue #16
* v1.1.0
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
* v1.0.0

LICENSE
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This software is released under the MIT License, see LICENSE