Frink is a practical calculating tool and programming language designed to make physical calculations simple, to help ensure that answers come out right, and to make a tool that's really useful in the real world. It tracks units of measure (feet, meters, kilograms, watts, etc.) through all calculations, allowing you to mix units of measure transparently, and helps you easily verify that your answers make sense. It also contains a large data file of physical quantities, freeing you from having to look them up, and freeing you to make effortless calculations without getting bogged down in the mechanics.

Here's a handy class for applications needing a way to deal with mathematical expressions input by the user. It accepts an NSString consisting of a well-formed mathematical expression, evaluates it, and returns the result. It supports arbitrary named variables, so it is also perfect for graph plotting applications.

A jQuery plugin to directly embed LaTeX into your website or blog