Reverse Polish Lisp, aka Reverse Polish Lisp, is a historical programming language created in 1984. RPL (derived from Reverse Polish Lisp according to its original developers, whilst for a short while in 1987 HP marketing attempted to coin the backronym ROM-based Procedural Language for it) is a handheld calculator operating system and application programming language used on Hewlett-Packard's scientific graphing RPN (Reverse Polish Notation) calculators of the HP 28, 48, 49 and 50 series, but it is also usable on non-RPN calculators, such as the 38, 39 and 40 series. RPL is a structured programming language based on RPN, but equally capable of processing algebraic expressions and formulae, implemented as a threaded interpreter. RPL has many similarities to Forth, both languages being stack-based, as well as the list-based LISP. Read more on Wikipedia...

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Example code from the Hello World Collection:

Hello World in RPL for the HP-28, HP-48, HP-49 and HP-50 series pocket calculators. No comments possible.

<<
    "HELLO WORLD"
    1 DISP
    60 FREEZE
>>

Example code from Wikipedia:

« 
   0       @ Start with zero on the stack
   1 10    @ Loop from 1 to 10
   FOR I   @ "I" is the local variable
      I +  @ Add "I" to the running total
   NEXT    @ Repeat...
»

Last updated November 16th, 2019