Re: [COFF] [TUHS] The most surprising Unix programs

On Fri, 20 Mar 2020, Grant Taylor via COFF wrote: [a] [square] [enter] [b] [square] [+] [sqrt] (You don't need those extra "enter" keys, as the display is implicitly the top of the stack.) 7. Well, "square" also needs the orange "shift" key, so that's really 9, but the number of keystrokes ain't exactly the point; it's not a race, but a method of thinking. [...] Well, it really comes down to the calculation that you are trying to perform. Trivial example: 1 + 1 = -> 4 keys. 1 enter 1 add -> 4 keys. I don't have an algebraic calculator right to hand, but I'd imagine that solving a second-order polynomial (without a built-in program!) would involve fewer keys when using RPN because of the stack for intermediate results; a quick estimate is around 30 keys (with single-digit numbers) to get one of the roots, and you could probably save the result of most of it on the stack for re-use to get the other root (and the 42S groks complex numbers as a bonus[*], but that's hardly as a result of RPN). The 42S also has a handy "swap x/y" if the operands are the wrong way around, another one to rotate the stack, etc. You don't do Computer Science without being exposed to RPN, and I had to wait for a salary-in-lieu payout (long story) before I could afford the 42S that I'd been drooling over (and forget the overpriced IR printer[#]). [*] 1 +/- SQRT => "0.00 i1.00" (I have the display precision set to 2 because I use it for monetary stuff a lot; the internal precision is 15 digits). [#] A dream of mine is to reverse-engineer the printer protocol, then grab it using a laptop camera. Here endeth today's HP-42S lesson... -- Dave