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I was reading through HP's 35 year anniversary page when I noticed this description of the HP-28C, near the bottom:

1987 HP-28C: First full RPL calculator
In the late 1980s, HP developed a new programming language
for its new series of extremely powerful calculators. By
combing (sic) elements of RPN, Lisp and Forth, HP came up
with a language called RPL (or ROM-based Procedural Language).

Is this just a marketing goof or is their precedent for this expansion of "RPL?"


Hi Howard.

Even though I already heard about that weird definition (see for example: http://en.wikipedia.org/wiki/RPL_%28programming_language%29)

I'd rather stick to what William C. Wickes (the RPL "founding father" :) says in his book "RPL: A Mathematical Control Language":

Several existing operating systems and languages were considered, but none could meet all of the design objectives.
A new system was therefore developed, which merges the threaded interpretation of Forth with the functional approach of Lisp.
The resulting operating system, known unofficially as RPL (for Reverse-Polish Lisp), made its first public appearance in June of 1986 in the HP-18C Business Consultant calculator

I took the quote from RPLman, as, alas, I don't have a copy of Bill Wickes' book :(

Hope this helps.

Best regards.


From "A Guide to HP Handheld Calculators and Computers" by W. A. C. Mier-Jedrzejowicz:

RPL stands for Reverse Polish Lisp - it combined the RPN calculator language of earlier models with features of the Lisp and Forth programming languages. For a time HP explained the letters RPL as an acronym for "ROM-based Procedural Language."

So there is precedent for this within HP. Perhaps "Lisp" and "Forth" were (and maybe still are) subject to copyright or trademark restrictions, so the "official" line had to be that RPL stood for something else.

I have never heard of copyright restrictions on the names of programming languages before, so I don't think that's the reason. I think it is merely that HP thought (probably rightly) that the phrase "Reverse Polish Lisp" would strike fear and terror into the hearts of almost anyone! (Members of this forum excluded, of course ;-)


Some non-members will spell-check it as "reverse polish lips", what might be associated with some makeup trick, i.e.: the usage of lipstick by passing it backwards (or in other unorthodox manner) to make the mouth to have a shiny appeareance.

Oh, RPN stands for "Reversely Polished Nails", by the way...