RPL

A truly horrible brain-damaged programming language used by HP48's. RPL is an unholy union between reverse polish notation and LISP. Either alone would be fine, LISP is a good programming language, RPN is good for calculations, but when they are combined, you have a hellish nightmare.

Stay away if you value your soul.

RPL is a decendant of Forth with the added benefit that it uses lambda bindings, like LISP and Scheme. It was specifically as a mathematical control language for the Hewlett Packard calculator series, and was introduced with the HP-18C Business Consultant calculator Used as the operating system, it offers tremendous calculator expandability; it is also a very funny language to hack in.