if your making a new language make sure to keep me informed... i have lots of suggestions on that topic 
<{POST_SNAPBACK}>
It is more like an old language. I'd be creating an HP49 language (HP calls it RPL) that uses the stack. This is different than most languages. I'll still keep you informed for suggestions and ideas
It would be very very nice if you could put HP CAS functions in CP.
oohhhhhhhhhh. I know this is impossible 
Finally I'll buy a HP49G+
<{POST_SNAPBACK}>
Oh, its possible all right, and I plan on doing it.
I have to create my own funtions for manipulating the stack, like DUP, SWAP, ROT. I also have to create functions that manipulate objects on the stack. For example LIST-> expands a list to the stack and leaves the list size on level 1 of the stack.
Since I have to create and handle my own functions, there is no reason why I can add
any function. In essence, The CP48 add-in will be a superset of the ClassPad. If I can manage it, you'll be able to write user defined programs or functions in Casio Basic
or in RPL (the HP49's language). This opens up a whole set of new code to the ClassPad. Anything that is written in RPL could be run on the ClassPad too

.
NOTE: When I use the term RPL, I mean user-RPL. User-RPL is the subset that is available directly on the calculator. System-RPL is the superset that is available if you write a library for the HP48/49 on the PC.
BTW, if anyone wants to see the prototype let me know. It has a full stackand editline, and has all the basic RPL stack functions like DUP, SWAP, ROT, etc.. It also handles all the ClassPad functions in RPN. For example you can enter...
X DUP SIN SWAP 2 ^ +
and get out sin(x)+x^2