Why do commands behave inconsistently?

[Joe Horn]

(03-25-2020 03:50 PM)Orome Wrote:  

victorvbc Wrote:  If you press Enter after selecting Sort, doesn't it sort the list?

Yes. The question is why selecting [REVERSE] reverses immediately, while [SORT] places SORT() in the command line (requiring a subsequent [ENTER]).

Just a hypothesis: Perhaps it's because REVERSE always and only allows one argument, but SORT allows either one or two arguments (see its Help screen). In RPN, REVERSE can assume that it will always and only take one argument from the stack. But SORT can only know whether to take one or two arguments if you tell it to, by typing SORT(1) or SORT(2), respectively. My hypothesis can be tested by seeing if similar behavior occurs with other single-argument functions and other multiple-argument functions.