You're comparing infix with RPN. There are more factors there than just number of keystrokes; not everyone enjoys working with RPN or finds it comfortable. RPN is a deliberate tradeoff in favor of speed/efficiency at the expense of other things.
The calculator I used in school was infix but, unlike this calculator, had:
- single buttons for common operations like +, * or sqrt
- no shifted parentheses
- display-style input of fractions and exponential so you got some visual clue if your brackets weren’t totally wrong
- single (sometimes shifted) buttons for functions like cos/tan/arcsin/…
- specialised shift operators which mostly meant inverse or hyperbolic
GNU Calc has most of these (+ and * are still shifted but all common operations are shifted. Parentheses are not used because of RPN. Display-style (‘big’) presentation is optional but ugly ascii art. Press H for hyperbolic, I for inverse).
I think gnu Calc is lacking a bit in entry of algebraic expressions but I don’t think speed crunch is better. I’d like to see something that let you place a ‘(‘ somewhere ‘backwards’, or in other words a feature for ‘I would like to parenthetical use some of the past expressions. Please let me interactively choose them without fiddling with cursor movement commands.’
