[Coco] DEF USR and strings?

[William Astle]

On 2025-10-29 14:48, Allen Huffman via Coco wrote:
> I could have swore I saw someone post (maybe on Facebook) that they realized the DEF USR could accept a string parameter. I had only known to use it like this:
> 
> A$=“STRING”
> X=USR0(VARPTR(A$))
> 
<snip>
> It looks like BEQ L8943 is where it goes if numeric, else it continues and gets the length and address of the string variable and continues.
> 
> What is the syntax to make this work?

First, you leave out VARPTR completely. It's not needed if you rely on 
USR to pass through a string parameter. (Under plain Color Basic, you 
can't pass a string in but Extended Basic lets you).

The biggest problem is that if you pass a string to USRn(), VALTYP will 
still be flagged as string when your USR routine returns and that will 
trigger a TM error on the assignment (to X in your example). Your 
handler routine will have to actually return a value instead of doing 
nothing with a simple RTS. Note that if you do things right, your USRn() 
handler can actually return a string but the how of that is beyond the 
scope of this email.

If you get a TM error *with* the VARPTR in there, then you have 
something else wrong.