xen is a high-level, interpreted language for analyzing and operating upon musical pitch structures within the context of "xenharmonic" microtonal theory. The interpreter is written in ES6 JavaScript and based off "AEL" by Peter Olson. xen is heavily reliant on tune.js, a library which models the xen data types as classes in JavaScript/TypeScript.
The online xen console includes the interpreter and can be used to evaluate expressions, like a sort of xenharmonic calculator.
Visit the Wiki for documentation.