pre-js-py v1.2.0

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PreJsPy

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What is this?

PreJsPy is highly configurable a precedence-based parser written in both Python and JavaScript. The default grammar is based on a subset of JavaScript but can be adapted to a lot of different scenarios.

.. code:: python

from PreJsPy import PreJsPy parser = PreJsPy() parser.parse("6 9 == 42") {'type': 'BinaryExpression', 'operator': '==', 'right': {'type': 'Literal', 'raw': '42', 'value': 42.0}, 'left': {'type': 'BinaryExpression', 'operator': '', 'right': {'type': 'Literal', 'raw': '9', 'value': 9.0}, 'left': {'type': 'Literal', 'raw': '6', 'value': 6.0}}}

.. code:: js

var PreJsPy = require('pre-js-py').PreJsPy; parser = new PreJsPy() parser.parse('6 9 == 42') { type: 'BinaryExpression', operator: '==', left: { type: 'BinaryExpression', operator: '', left: { type: 'Literal', value: 6, raw: '6' }, right: { type: 'Literal', value: 9, raw: '9' } }, right: { type: 'Literal', value: 42, raw: '42' } }

The JavaScript version of this library has been adapted from the JavaScript library JSEP which is (c) 2013 Stephen Oney, http://jsep.from.so/ and has been published under the terms of the MIT license. The code has been ported to Python and a lot of utility functions have been added.

Grammar Features

• Symbolic Values
  • Constants
    • such as true, false and null
    • configurable: Arbitrary constants can be added
  • Identifiers
    • may contain $,_ or alphanumeric chacraters but may not start with a number
    • can include property names and accessors, for example foo, bar.baz, foo['bar'].baz
• Various types of literals
  • Numeric Literals (42.001)
    • decimal notation (-42)
    • exponential notation (6.7E-10)
  • String Literals ("Hello world")
    • can be either double or single quotes
    • special characters can be escaped
  • Array Literals ([1, 2, 3])
    • must be surrounded by square brackets
    • can be nested
• Multiple types of operators
  • Unary operators
    • by default -, !, ~ and +
    • custom operators can be added, existing ones can be removed
  • Binary operators
    • precedence based
    • by default contains all JavaScript operators
    • custom ones can be added with custom precedences
    • brackets can be used to override precedences
  • JavaScript Conditional operator
    • single ternary operator a ? b : c
• Call Expressions
  • must use round brackets
  • for example Math.cos(x)

API

The API in JavaScript and python are almost identical. The only differences come from the features of the languages themselves.

.. code:: javascript

var parser = new PreJsPy(); // creates a new parser

parser.getConstants() // returns an object containing constants parser.setConstants(d) // sets the current constants know to the parser

parser.getUnaryOperators() // gets an array of unary operators parser.setUnaryOperators(ary) // sets an array of unary operators

parser.getBinaryOperators() // returns an object mapping binary operators to their precedence parser.setBinaryOperators(ary) // sets the binary operators to precedence mapping

parser.parse(s) // parses a string into a AST

.. code:: python

parser = PreJsPy() # creates a new parser

parser.getConstants() # returns an object containing constants parser.setConstants(d) # sets the current constants know to the parser

parser.getUnaryOperators() # gets an array of unary operators parser.setUnaryOperators(ary) # sets an array of unary operators

parser.getBinaryOperators() # returns an object mapping binary operators to their precedence parser.setBinaryOperators(ary) # sets the binary operators to precedence mapping

parser.parse(s) # parses a string into a AST

Install

This package is published on the Python Package Index <https://pypi.python.org/pypi/pre_js_py>_ Installation can be done simply via pip:

.. code:: bash

pip install pre_js_py

It is also published on Nodejs Package Manager <https://www.npmjs.com/package/pre-js-py>_ Installation can be done simply via npm:

.. code:: bash

npm install pre-js-py

License + Acknowledgements

This module and associated documentation is Copyright (c) Tom Wiesing 2016 and licensed under the MIT license, see license <LICENSE>_ for details.