Walkthrough of an RPL program for an RPN programmer

[Albert Chan]

Hi, rprosperi and Thomas Klemm:

Thank you both. I think I get the gist of it.

RPL scoping rule have to think in reverse too.

For Lua, we open the scope *before* local variables: do local x, y, z = 1, 2, 3; ... ; end

For RPL, above is done in reverse: -> x y z << ... >>

Also, << ... >> have double meaning.
If preceded by locals setup, it open the scope.
If not, it turn whatever inside, as code object.

Double meaning also apply with +
If 2 items on stack is number, it replace them with their sum
If 2 items on stack is list, it replace them with concatenated list (just like Python)

Possibly even more than double meaning for +, say for string arguments ...