In contrast with the built-in iOS calculator? RPN and unit conversions, primarily, but also occasionally other functions like exponentiation, etc.
The built in iOS calculator does have exponentiation (in landscape mode), FYI.
My question was more 'what are you doing that need complex calculations?'
I don't know what RPN is btw.
"Reverse Polish Notation"[0], commonly used on Hewlett-Packard calculators, and considered a superior means of entering calculations on a calculator versus the way most calculators work. Considered by many to be reason enough to switch calculators.