[Coco] Mod10 Suggestions

[William Mikrut]

I am definitely going to try it later.

I won't be near my console until tomorrow... but believe me, I am dying to
code/try it!

On Feb 17, 2017 10:15 PM, "Brett Gordon" <beretta42 at gmail.com> wrote:

> Ok.. this actually works on a calculator on my bank card.  A zero is
> prepended so it shifts the odd/even digits around, and we do need to add
> digits of shifted bytes ;(
>
>    Ldy #num     y points to beg of number
>    Ldx #0           x is an 16 bit accumulator
> loop:
>    ldd ,y++      get next word
>     abx             accum even digit
>    lsla             shift odd digit
>     cmpa #10 add digits if > 9
>     blo skip
>     suba #9
> skip:
>    tfr a,b            no aax ;(
>   abx              accum odd byte
>    cmpy #num+16
>    bne loop
> * find mod
>    tfr x,d        full bit tests only in D :(
> again
>    subd #10   subtract 10 until we go neg
>    bpl again
>    addd #10  went too far! Add back last 10
> * result in D (0= good cksum)
>    beq beep   like at the supermarket
>    bra boop   bad swipe
>
> I get ~34 bytes of code + 16 data + 0 stack. Although the pcr addressing
> would add a few bytes of code and data.
>
> cheers
>
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