Re: 2ROT OR NOT TO 2ROT that is the question

hi
There's not enough stuff on the stack for a 2ROT. Use 2SWAP.
Or re-arrange to do the ALPHA * to the input first and add the (1-ALPHA) *
LAST-VAL after; then you don't need 2SWAP .

At 12:34 PM 7/23/02 -0700, Gene Silvernail wrote:
>The following code is for a simple exponential averaging filter. It
>doesn't work. As best as I can see the 2ROT screws up the first time
>through. Pre-loading LAST-VAL with 0. and giving ALPHA a value of 50 you
>can run successive 0. X1000 LAST-VAL 2@ D. and see the results.....
>We are running
>SwiftX AVR 3.1.4
>
>Any light would be helpful.
>
>Gene Silvernail
>
>AIM JULY 22, 2002 ok
> ok
> ok
>0. x1000 LAST-VAL 2@ D. 21561344 ok
>0. x1000 LAST-VAL 2@ D. 10780672 ok
>0. x1000 LAST-VAL 2@ D. 5390336 ok
>0. x1000 LAST-VAL 2@ D. 2695168 ok
>0. x1000 LAST-VAL 2@ D. 1347584 ok
>0. x1000 LAST-VAL 2@ D. 673792 ok
>0. x1000 LAST-VAL 2@ D. 336896 ok
>0. x1000 LAST-VAL 2@ D. 168448 ok
>0. x1000 LAST-VAL 2@ D. 84224 ok
>0. x1000 LAST-VAL 2@ D. 42112 ok
>0. x1000 LAST-VAL 2@ D. 21056 ok
>0. x1000 LAST-VAL 2@ D. 10528 ok
>0. x1000 LAST-VAL 2@ D. 5264 ok
>0. x1000 LAST-VAL 2@ D. 2632 ok
>0. x1000 LAST-VAL 2@ D. 1316 ok
>0. x1000 LAST-VAL 2@ D. 658 ok
>0. x1000 LAST-VAL 2@ D. 329 ok
>0. x1000 LAST-VAL 2@ D. 164 ok
>0. x1000 LAST-VAL 2@ D. 82 ok
>0. x1000 LAST-VAL 2@ D. 41 ok
>0. x1000 LAST-VAL 2@ D. 20 ok
>0. x1000 LAST-VAL 2@ D. 10 ok
>0. x1000 LAST-VAL 2@ D. 5 ok
>0. x1000 LAST-VAL 2@ D. 2 ok
>0. x1000 LAST-VAL 2@ D. 1 ok
>0. x1000 LAST-VAL 2@ D. 0 ok
>0. x1000 LAST-VAL 2@ D. 0 ok
>0. x1000 LAST-VAL 2@ D. 0 ok
>0. x1000 LAST-VAL 2@ D. 0 ok
>
>
>
>
>
>
>{
>========================================================================
>=
> Belhaven Applied Technologies Inc. -- G.P.Silvernail
>
> Created: 07-22-2002, 03:47 PM
>
> Project: AIM
> File: FILTERS.f
> Path: D:\ForthInc\ProjectS\AIM
>
> Comment: Filters, all use double numbers
>
> Exponential Averaging, y(n) = ALPHA * x(n) + (1-ALPHA) * y(n-1)
> where y(n-1) = last Exponential Average
>
>========================================================================
>= }
>
>SAVE-SECTIONS
>
>UDATA
>
>2VARIABLE LAST-VAL \ Holds the last value or y(n-1)
>VARIABLE ALPHA \ Holds 0 to 100
>
>RESTORE-SECTIONS
>
>: EXP-AVG ( d1 -- d2 ) \ Expects double d1 which is
>raw reading
> ;
>[DEBUG
>: X1000 ( d -- )
> LAST-VAL 2@
> 100 ALPHA @ - 100 M*/
> 2ROT \ <<<<<< 2ROT GETS CLOBBERED
>HERE FIRST TIME THROUGH >>>>>
> ALPHA @ 100 M*/
> D+ LAST-VAL 2!
>
> ;
>DEBUG]
>
>
>: INIT-MATH
> 50 ALPHA !
> 0. LAST-VAL 2!
> ;
>
>
>
>
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MrBill
~|:)>>>>
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Received on Tue Jul 23 2002 - 13:25:25 PDT