Rpn

This is reverse polish notation calculator.
Usage:     rpn [number | operator ...]
Example1   'rpn 2 3 +' will add 2 and 3. (2+3)
Example2   'rpn 2 3 4 + *' will add 3 and 4 and multiply with 2. (3+4)*2

Operators: * + / % - ^
Functions: sin random sqrt cos asin exp log negate tan atan acos
Constants: EUR e pi
All angles are in radians.