Hi Scott.

You are absolutely right. I didn't say actually 2 clocks did I ? ;)
I was thinking about extending previous case by one more command.

2x-1 = 2(x-1)+1

which Ruben Jvnsson has perfectly found.

decf    X,F     ;0 -> 0xFF
setc
rlf     X,F     ;0xFF<1 -> Cy=1,0xFF


WBR Dmitry.


Scott Dattalo wrote:
>
> On Thu, 6 Jun 2002, Dmitriy A. Kiryashov wrote:
>
> > Hi Scott.
> >
> > >    decf  x,w    ;w = x-1
> > >    addwf x,f    ;x = x+x-1 = 2*x-1
> >
> > What about case when x == 0 ?
> >
> > 0 + 0xFF = 0xFF and Cy=0 (should be Cy==1(borrow) )
>
> I'm not going to play anymore if you change the rules :) (In other words,
> I can't see a 2-instruction solution that handles the carry as you request
> here.)
>
> Scott

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