mr-parser

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> Parses mathematical expressions and outputs an AST

- Description
- why?
- Grammar
- Install
- Usage
- API
- Parser = require('mr-parser').Parser
- Parser.parse(expression)

Description

mr-parser is a lightweight mathematical parser inspired by [math.js expression parser][math-js], unlike [math.js expression parser][math-js] the AST nodes contain no info on how to compile a node which makes the parser modular

$3

I felt that I had to make another parser because:

- math-parser is too simple for me, it just operates on numbers and has the following operators +, -, *, / and ^ and doesn't have variable substitution
- [math.js expression parser][math-js] is perfect but it's not modularized yet, to use it one would have to include all the source code of math.js
- [math.js expression parser][math-js] AST nodes have info about how to compile a node, I think it's better to let another module do that

$3

``text
program : block (; block)*

block : assignment

assignment : ternary
| symbol = assignment

ternary : logicalOR
| logicalOR ? ternary : ternary

logicalOR : logicalXOR
| logicalXOR (||,or) logicalOR

logicalXOR : logicalAND
: logicalAND xor logicalXOR

logicalAND : bitwiseOR
| bitwiseOR (&&,and) logicalAND

bitwiseOR : bitwiseXOR
| bitwiseXOR | bitwiseOR

bitwiseXOR : bitwiseAND
| bitwiseAND ^| bitwiseXOR

bitwiseAND : relational
| relational & bitwiseAND

relational : shift
| shift (!= | == | > | '<' | '<=' |'>=') shift)

shift : additive
| additive (>> | << | >>>) shift

additive : multiplicative
| multiplicative (+ | -) additive

multiplicative : unary
| unary (* | / | %) multiplicative
| unary symbol

unary : pow
| (- | + | ~) unary

pow : factorial
| factorial (^, '**') unary

factorial : symbol
| symbol (!)

symbol : symbolToken
| symbolToken functionCall
| string

functionCall : ( )
| ( ternary (, ternary)* )

string : ' (character)* '
: " (character)* "
| array

array : [ ]
| [ assignment (, assignment)* ]
| number

number : number-token
| parentheses

parentheses : ( assignment )
: end

end : null-token
`

Install

`sh
$ npm install --save mr-parser
`

Usage

`js
var Parser = require('mr-parser').Parser;
Parser.parse('1 (2 + 3) 4')

// returns
{
blocks:[{
op: '*',
args: [{
value: '1',
valueType: 'number'
}, {
op: '*',
args: [{
op: '+',
args: [
{ value: '2', valueType: 'number' },
{ value: '3', valueType: 'number' }
]
}, {
value: '4',
valueType: 'number'
}]
}]
}]
}

Parser.parse('2x')

// returns
{
blocks: [{
op: '*',
args: [
{ value: '2', valueType: 'number' },
{ name: 'x' }
]
}]
}
`

API

$3

#### Parser.parse(expression)

params
* expression` {string} the expression to be parsed

returns
* Returns an array of possibly nested nodes which is the AST that represents the expression

[math-js]: http://mathjs.org/docs/expressions/index.html

2015 MIT © [Mauricio Poppe]()