Free42: Unlimited-length strings and other type extensions

[Thomas Okken]

(01-25-2021 03:24 AM)Paul Dale Wrote:  I do wonder if Free42 is becoming more RPL like over time. When thinking about extending the WP 34S, I started to understand the decisions behind the 28 series. The more I dug into it, the more RPL looked like the most natural successor to RPN.

I agree about RPL being the natural successor to RPN. Thinking about Free42 internals has made me come to understand and appreciate the logic behind the RPL design a lot more.

However, I don't want to create an RPL clone. I do still find keystroke programming easier, probably because it's just a better fit for the limitations of a small screen and keyboard. When editing RPL, the calculator always feels cramped and I find myself wishing for a QWERTY keyboard and a screen that can display way more text. And the absence of goto, break, and continue is annoying.

So I'm coming at is from the opposite direction: what can I add to Free42 to make it more capable, while maintaining the HP-42S look and feel? The big RTN stack and local variables address the inability to write recursive functions or create complex programs without littering the catalogs with variables, and SST→ and SST↑ were necessary because debugging long programs was just too painful without them. And FUNC helps create easily reusable functions.

With the things I'm working on now, my motivation is a bit different, since those are mostly features that I have often been asked to implement, not features that I myself have a need for... but once I started thinking about how to implement them, once again I found myself thinking of RPL, because lists suddenly appear to be very useful. I'm also reminded of the HP-42S design, in that some RPL features can be useful for implementing things behind the scenes, without necessarily making them available in user code.

Before I go crazy adding new functions, I am going to have to think about how to extend the raw file format, because the gaps left in the HP-42S opcode space are starting to fill up. Plenty of XROMs, of course, but functions with parameters are trickier...