Re: [Amforth-devel] words: tuck/under etc

[Bernard M. <bme...@gm...>]

Hi Michael,

I implemented the "Elegant FSM" version of Julien's code Section 3.3 i.e:

The FSM is then defined as

4 WIDE FSM:
\ input:  |  other?  |  num?   |  minus?  |   dp?     |
\ state:  ---------------------------------------------
   ( 0 )     DROP >0    EMIT >1   EMIT >1     EMIT >2
   ( 1 )     DROP >1    EMIT >1   DROP >1     EMIT >2
   ( 2 )     DROP >2    EMIT >2   DROP >2     DROP >2 ;


That seems to me the most readable and flexible of all his examples.
I have given Mathias the code for including in the Lib.

Cheers,
Bernard.

On Thu, Jul 17, 2008 at 5:16 AM, Kalus Michael <mic...@on...>
wrote:

> Hi Bernard.
>
>
> Am 15.07.2008 um 03:03 schrieb Bernard Mentink:
>
> > And lastly, the FSM code is:
> >
> > : FSM:       ( width -- )  CREATE  ,  ]
> >         DOES>  ( n adr -- )
> >                TUCK  @  mystate @  *   +   CELLS   CELL+  +
> >                ( adr')  PERFORM  ;
> >
> >  I notice he enters into compile mode with the "]" word just before
> > the
> > DOES> word, is that necessary to do with the latest CREATE/DOES code?
>
> In the meantime I studied Nobles Code (1). Hope I got it right what
> he is doing there.
>
>
> This is what the ] does:
>
> He ceates a defining word called FSM: and during compiletime of FSM:
> the ] is compiled into the definition. At runtime of FSM: the ] is
> executed. Now this starts compilation of all the words following the
> word defined by the defining word until the closing ; enters
> execution again.
>
>
> In Nobles example "3.2. A Better FSM" FSM: defines <Fixed.Pt#> and
> thereafter compiles the list of execution tokens:
>
> 4 WIDE FSM: <Fixed.Pt#>   ( action# -- )
> \            other   num    -     .      \ state
>              DROP    (00)  (00)  (02)    \ 0
>              DROP    (00)  DROP  (02)    \ 1
>              DROP    (02)  DROP  DROP  ; \ 2
>
>
> If you do not want to use that ]-trick, because it makes your program
> code more mysterious,  you archive the same result this way:
>
> 4 WIDE FSM: <Fixed.Pt#>   ( action# -- )
> \              other       num        -        .         \ state
>              ' DROP ,    ' (00) ,  ' (00) ,  ' (02) ,    \ 0
>              ' DROP ,    ' (00) ,  ' DROP ,  ' (02) ,    \ 1
>              ' DROP ,    ' (02) ,  ' DROP ,  ' DROP ,    \ 2
>
> This way it is more obvious what comes into the array.
>
>
> So the use of ] has nothing to do with the CREATE/DOES Part of
> creating a new defining word. ok?
>
> Michael
>
>
> (1) Finite State Machines in Forth; J. V. Noble
>     http://dec.bournemouth.ac.uk/forth/jfar/index.html
>
>
>
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