infix-postfix

This package allows you to convert infix expressions to postfix expressions.

Installation

npm install infix-postfix

Usage

Importing

import infixToPostfix from "infix-postfix";

or

const infixToPostfix = require("infix-postfix");

Converting

to a string

console.log(infixToPostfix("(a+2b)^-2").toString());

/* Output:
    a 2 b * + 2 − ^
*/

to an array

console.log(infixToPostfix("(a+2b)^-2").toArray());

/* Output:
    [
      'a', 2, 'b', '*',
      '+', 2, '−', '^'
    ]
*/

Examples

2+3*4 ▶ 2 3 4 * + a b(3+4)2 ▶ a b * 3 4 + * 2 * -12-3 ▶ 12 − 3 - 12^-2 ▶ 12 2 − ^ ((2cm+112)*12.2/3)^2 ▶ 2 cm * 112 + 12.2 * 3 / 2 ^

Features

Operator parsing

+, -, *, /, (), ^ get parsed to + (addition), - (subtraction), − (negation), * (multiplication), / (division) and ^ (exponentiation). The difference between - and − is, that − (negation) is an unary operator (e.g. -4 gets parsed to 4 −) and - (subtraction) is a binary operator (e.g. 2-6 gets parsed to 2 6 -). There is no unary + operator, because one can simply ignore such for mathematical reasons.

Operator reduction

Unnecessary operators get removed automatically. For example ---+4 gets parsed to 4 −, +(12) gets parsed to 12.

Number parsing support

Numbers get parsed. Obviously only works with the toArray() method.

Variable support

Any variable not containing operator characters (+, -, ...) is supported. For example a-6 gets parsed to a 6 -.

Multiplication shortcut support

A common parser would parse b/10b to b 10b / - which is unfortunately wrong. This parser recognizes that 10 and b are different operands. It parses the string to b 10 b * /. Added to that a b gets parsed to a b *. Furthermore a(3)2 is translated to a 3 * 2 *.