3 ms·

So are array languages polish notation? +/!100 feels like the opposite way you'd write it in some kind of RPN concatenative language 100 ! [ + ] /

• Jtsummers 5y ago
  Not quite. + isn’t the last thing done (which it would be in Polish notation). Instead it’s done during the / operation. Polish notation would be lisp (or the notion most people have for lisp, special forms and macros break it up a bit).
  • LAC-Tech 5y ago
    Lisp is polish notation for trees of variable arity. hence all the parens - you need some way to group them. So in some K flavoured LISP I think it would be ((/ +) (! 100))
    • zdkl 5y ago
      Or in clojure with the threading macro (->> 100 range (reduce +)) which is equivalent to this, without the macro (reduce + (range 100))
      • LAC-Tech 5y ago
        yes, quite a bit more long winded than K
• CraigJPerry 5y ago
  You read it strictly right to left, weird idea to me but it’s common in the array languages - j and APL do it this way too. I believe the reasoning is something like Iverson (or maybe Whitney) didn’t like the complexity of PEMDAS in maths so decided on this rule.
  • razetime 5y ago
    Iverson wanted consistent symbols and rules for math notation. So it's math first, then programming language next. Makes it extremely strong with describing algorithms, but gets a bit complicated for programming.
• tzs 5y ago
  In Polish notation all the operators are prefix operators. In APL family languages there are infix operators and prefix operators. Prefix operators take as their operand the result of everything to their right. Infix operators take as one operand everything to their right and take as their other operand the first thing on their left.