Rather Ian with harder/stronger I than John.
Well Polish it is not that hard.
It's only second hardest language on the world (China I look at you)
If it is hard for you. Well try to spell this thing correctly
"Zażółć żółtą jaźń" or "Chrząszcz brzmi w trzcinie"
Sorry for OT.
All thing look really amaizing. I'd love to see more in this topic.
After I got used to RPN (I had a lovely old HP-21) I found it much more intuitive. Stack-based thinking. No parentheses! (And I've used LISP for years, but that's entirely different.)
RPN vs Infix/Algebraic used to be a holy-war topic. Like emacs vs vi, or iPhone vs Android.
The one issue I've already had with RPN is that you require a separator between numbers anyways - in RPN it's too easy to parse "23 4 +" as "2 34 +", for example, especially if you're writing quickly.
On the HP calculators the separator would usually be the enter key. I think the old ones displayed just the top entry of the stack, on the newer ones with bigger display you see the stack with each entry on one line.
The joke has been going on for quite some time now - Lisp and related languages use Polish Notation everywhere.
(The main benefit is that (R)PN is parenthesis-free, so it makes it easier for a calculator to process expressions with multiple operators. The use in programming languages is nonexistent but to make clear that +, *, .. are just like any other function call, where you would naturally use polish notation.)
Forth is arguably the best language in terms of expressive power/language complexity, though that's largely due to the denominator.
It's a great choice for tightly constrained devices, though far fewer devices have such constraints now. The mental overhead of having to track stack-effects for each function makes it difficult to scale to large systems and maintain productivity, but if you're trying to eke every iota of power out of a chip with a tiny amount of ROM, it's hard to beat a direct-threaded (or token-threaded...) Forth.
I don't know about less ambiguous, it can still require only single token lookahead and be context-free without any parentheses, but Lisp-ish languages are easier to parse because you have fewer productions to worry about compared to more complex languages.