[Coco] Does DEF FNX for Basic only take one parameter?

[Boisy G. Pitre]

John ,

After reading Art's reply, I realize that John was talking about DEF 
FN, and not DEFUSR.  Sorry for the apparent brain fart...  I guess my 
mind was so into the problem that I had, I saw "DEF" and went nuts :)

Boisy

On Mar 31, 2004, at 8:45 AM, Boisy G. Pitre wrote:

> John,
>
> I was looking at the USRx entry point routines myself recently.  
> However, instead of just passing one parameter, I need to pass about 5 
> or 6.  I found that USRx was just too limiting for what I needed, so I 
> just use wrote my assembly routine to live at $7000 and reserved some 
> parameter space in high RAM ($7100) where I POKE the parameter values. 
>  I then do an EXEC &H7000 from BASIC and wait for the routine to 
> finish.  When it does, it returns control to BASIC nicely.
>
> I have found the explanation of DEFUSR/USR in the CoCo 3 BASIC book to 
> be a bit terse, and lacking specifics.  For a better explanation, 
> check out the "Getting Started WIth EXTENDED Color BASIC" book that 
> came with most later CoCo 2s.  Its explanation of DEFUSR/USR on pages 
> 197-202 go into much more detail.
>
> As for passing a "parameter list", you could possibly pass the address 
> of an array using VARPTR.  The array could have two, three or twenty 
> values and the assembly routine could go down the list of them.  Still 
> a bit awkward, though.
>
> Also, you need to call INTCNV in BASIC ROM from your assembly routine 
> in order to use the passed value into USRx(), as the number passed is 
> in BASIC's floating point format.  INTCNV converts a BASIC number into 
> an integer and places it in reg D.
>
> Again, the CoCo 2 book has much better information on the use of these 
> calls.
>
> On Mar 30, 2004, at 11:08 PM, John Guin wrote:
>
>> Hello all,
>>
>> I was working on a basic program to do something like:
>> DEF FNX(A,B)= some function of A and B
>>
>> Basic gives a syntax error for this, but my Coco3 book says I can 
>> pass a
>> parameter list to it.
>>
>> I'm assuming the book is wrong, and DEF FNx can only take one 
>> paramater, but
>> does anyone know if that's right?
>>
>> Thanks,
>> John
>>
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>
>
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