[Coco] DEFUSRn parameters vs. Color Extended BASIC manual

[Joel Rees]

Thanks, Arthur and William, for the confirmation about the conversion
routines INTCNV and GIVABF.

I'm playing with the USRn interface and I think it is clear that the Color
Extended BASIC manual, in addition to containing typos, contains errors in
the descriptions.

When passing a string in, if you pass it with VARPTR giving the address, if
the return value is stored in a string varable, it says TM error (type
mismatch). But if you store it in a numeric, it doesn't complain. But the
value in X is not the address of the string.

If you pass it without VARPTR, if the return value is stored in a numeric,
it gives type mismatch. But if you store it in a string, it doesn't
complain, and the address in X is the address of the string, as described.

Since the VARPTR is an integer, I'm guessing that the address passed that
way gets passed as a numeric, requiring conversion by INTCNV to recover,
which would require the BASIC interpreter to do less magic interpretation
of user intent. I suppose I should test that after I get some sleep.

Typical Microsoft misspecification, really.

And it leaves me inclined to pass integers as hexadecimal numbers stored to
strings, rather than depend on INTCNV and GIVABF.