evaluatex

This npm package is a placeholder for a coming, npm-optimized version of evaluatex.

arthanzel.github.io/evaluatex

Evaluatex

Evaluatex is a parser that reads and evaluates LaTeX and ASCII math. Use in Node, Angular, or with vanilla Javascript on both clients and servers.

Evaluatex can safely resolve math without relying Javascript's native eval() function. It can also support custom variables and functions, so you can pass in arbitrary values without having to hard-code the math.

Evaluatex is in development. It is in a functional state, but may do weird and unexpected things such as eating your cat.

Installation

$ npm install evaluatex # (coming soon!)
$ bower install evaluatex # (coming soon!)

// Node.js
var Evaluatex  = require("evaluatex");

// Angular V1
angular.module("myModule", ["evaluatex"])
.service("MyService", function(Evaluatex) {});

<!-- Vanilla JS -->
<script src="evaluatex.js"></script>
<script type="text/javascript">
	console.log(Evaluatex);
</script>

Building

npm test will run a set of unit tests defined in ./test/evaluatex.spec.js. These tests run in Node, and not in any browser runtime.

npm run compile will build the full script to ./evalulatex.js. You can include this in your HTML files.

Usage

> Evaluatex.evaluate("1 + 2 * 3 ^ 4")
163
> Evaluatex.evaluate("sin(0.5PI) + magic", { magic: 3 })
4

Features

By default, Evaluatex acts in ASCII mode. To use LaTeX-specific behaviour, pass in { latex: true } as the third argument to Evaluatex.evaluate. Read on to learn more.

Evaluatex supports all of the features you should expect from a simple calculator, including order of operations. Exponents use the ^ operator.

> Evaluatex.evaluate("1 + 2 * 3 ^ 4")
163

You can use variables in expressions that are visible to the expression only:

> Evaluatex.evaluate("1 + a / b", { a: 3, b: 4 })
1.75

Implicit multiplication with parens or variables is not a problem.

> Evaluatex.evaluate("4a(1+b)", { a: 3, b: 4 })
60

You have full access to Javascript's Math object, including all functions and constants.

> Evaluatex.evaluate("sin(0.5PI) + magic", { magic: 3 })
4

You can omit parens from simple functions, but be careful with implicit multiplication.

> Evaluatex.evaluate("sin 2PI") // Interpreted as sin(2) * PI
2.8566
> Evaluatex.evaluate("sin PI^2") // Interpreted as sin(PI^2)
-0.43

There is no globally-accepted standard for treating coefficients inside paren-less functions. Whenever in doubt, use parentheses.

You can even define custom functions.

> Evaluatex.evaluate("incr(4)", { incr: function(x) { return x + 1; } })
5

Multi-argument functions work just as well, but you need to include parentheses.

> Evaluatex.evaluate("hypot(3, 4)")
5
> Evaluatex.evaluate("min(5,4,3,2,1)")
1

There's even functions built right in to Evaluatex to help with logs, roots, and trig:

> Evaluatex.evaluate("logn(81, 3)")
4
> Evaluatex.evaluate("rootn(8, 3)")
2
> Evaluatex.evaluate("csc(0.25PI)")
1.414

Absolute values work like a charm...

> Evaluatex.evaluate("|5 - 20|")
15

...as do factorials, which round to the nearest integer before performing the calculation:

> Evaluatex.evaluate("3.6!")
24

LaTeX-specific behaviour

Turn on LaTeX idiosyncrasies with { latex: true } in the third parameter:

> Evaluatex.evaluate("x^24", { x: 2 }, { latex: true })
16

The previous example is evaluated as x^(2) * 4, since LaTeX often takes only the first digit of a number for such operations. Use curly braces ({ and }) to fix that:

> Evaluatex.evaluate("x^{24}", { x: 2 }, { latex: true })
16777216

If you try to use parens or square brackets, Evaluatex will complain.

> Evaluatex.evaluate("x^(24)", { x: 2 }, { latex: true })
Error!

LaTeX thinks that the above expression means x^'(' * 24), which is clearly bogus syntax. When in doubt, always use braces.

One more example:

> Evaluatex.evaluate("\\frac 123") // Interpreted as (1/2) * 3
1.5