[Coco] BASIC09 - unsigned INTEGERs?

[Allen Huffman]

> On Feb 1, 2015, at 5:53 AM, K. Pruitt <pruittk at roadrunner.com> wrote:
> 
>>> 
>>> On Jan 31, 2015, at 8:42 PM, Robert Gault <robert.gault at att.net <mailto:robert.gault at att.net>> wrote:
>>> 
>>> You don't need to go quite that far to just print the result. If you want to do 32-bit math you might need to separate the four bytes.
>>> As suggested by others, conversion of the hex words to reals might get around the negative integers.
>> 
>> Yes, I’d love to see someone who can figure this out. I tried all of that with no luck. Even did things like this:
>> <SNIP>
> 
> PROCEDURE filesize
> TYPE Registers=CC,A,B,DP:BYTE; X,Y,U:INTEGER
> DIM regs:Registers
> DIM path,callcode:BYTE
> OPEN #path,"test":READ
> callcode=$8D
> regs.A:=path
> regs.B=$02
> RUN SysCall(callcode,regs)
> CLOSE #path
> PRINT regs.U
> 
> It works.


Yes, if the file is less than 32767 bytes :) If it’s larger, it prints a negative number. And if it’s larger than 64K, that won’t work at all because the rest of the value is in X.

I am glad you are looking at this. We have THREE workarounds proposed now:

1. When creating a REAL that uses regs.X and regs.U, do a little check before deciding what to add: b < 0 then b=b+65536

2. Using the address of an INT variable and PEEKing out the bytes, and building it as three bytes manually.

3. Curtis thinks what they did was use BYTEs for the Registers structure:

TYPE Registers=CC,A,B,DP:BYTE; X1,X2,Y1,Y2,U1,U2:BYTE

I tried this tonight, and it worked fine. After the call, you put things back together like you want:

DIM filesize:REAL

filesize = x2 * 65536 + u1 * 256 + u2

…something like that.

#3 solves my situation, since I was really wanting to get the SysCall result back and use it. BUT, it doesn’t help with the general issue of dealing with INTEGERS. I guess the easiest thing to do is just use REAL if you need a value > 32767. :)

		— A