mathexpvalidator

Mathematical Expression Validator

Dependencies:

mathtokenizer: ^1.0.8

Library:

shunt: shunting function that takes string input and returns either 0 (if mismatched parentheses) or an array of objects {type, value}, an implementation of the shunting-yard algorithm (with unary operator, and nested function support)

validate: validating function that takes string input and returns an array: [0 || 1, "Error or Success message"] validate can also take optional arguments such as an array fuctions of accepted function names, and an array of variables: validate(expression, functions(optional),variables(optional))**

Examples:

To run these examples, just install the package in your directory:

npm i mathexpvalidator

And add the example code to your js file and then run it

Example 1:

const validator = require('mathexpvalidator');
let output = validator.shunt("-sin(1/x)");
/*
	output = [
	 token { type: 'number', value: '1' },
  	 token { type: 'variable', value: 'x' },
  	 token { type: 'operator', value: '/' },
  	 token { type: 'function', value: 'sin' },
  	 token { type: 'unary_operator', value: '-' }
	]
*/
let status = validator.validate("-sin(1/x)");
//status = [ 1, 'Valid expression' ]

Example 2:

const validator = require('mathexpvalidator');
let output = validator.shunt("(1+x)\*(x-");
//output = 0 (because of mismatched parentheses)
let status = validator.validate("(1+x)\*(x-");
//status = [ 0, 'Mismatched parenthesis' ]

Example 3:

const validator = require('mathexpvalidator');
let output = validator.shunt("x-1+");
/*
	output = [
  	 token { type: 'variable', value: 'x' },
  	 token { type: 'number', value: '1' },
	 token { type: 'operator', value: '-' },
	 token { type: 'operator', value: '+' }
	]
*/
let status = validator.validate("x-1+");
//status = [ 0, 'Insufficient operands' ]

Example 4: Using functions, variables optional arguments

const validator = require('mathexpvalidator');
const func = ["cos", "cosh", "acos", "sin", "sinh", "asin"];
const vari = ["x"];
let status = validator.validate("cosh(x)", func, vari);
//status = [1, 'Valid expression']

Example 5: Using the same func and vari arguments from example 4 but with an added variable t in the expression

const validator = require('mathexpvalidator');
const func = ["cos", "cosh", "acos", "sin", "sinh", "asin"];
const vari = ["x"];
let status = validator.validate("cosh(x*t)", func, vari);
//status = [0, 'Variable name not allowed']