t-rex 2.2

This is a terminal curses RPN calculator similar to the traditional calculators from Hewlett Packard. See https://www.hpmuseum.org/rpn.htm for info on RPN (Reverse Polish Notation). New in 2.1: Added 'e' for entering exponents directly into X. 2.2: Allowing for negative exponents (use 'H' to enter a minus sign).