If you are implementing a stack oriented interpreter, you may want to
take look at the lagnuage Forth (used to be very hot about 15 ago). Take
a look at the operators they use for expressions, stack manipulation,
flow control, etc. This will give you some ideas. I presume you can also
get a free implementation of Forth and play with it.

http://www.forth.org/

Tal

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Spehro Pefhany
> Sent: Friday, May 30, 2003 5:57 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]: Parser
>
>
> At 12:12 PM 5/30/2003 +0200, you wrote:
> > > You can implement what you want as bytecode in the eeprom and a
> > > bytecode interpreter that runs in the pic and executes
> it. Eg. for
> > > the expression above it would be in byte code something
> like (after
> > > correcting the & in the middle to && which is likely what you
> > > wanted):
> > >
> > > !fetch var1 !fetch var2 !and !sgn !fetch var3 !literal
> > > 0x0C !sub !sgn !and !if !literal DoSomething !acall !fi
> > >
> > > where each word would take one EEPROM cell or more (you
> can compress
> > > some of it).
> >
> >Ok, It sounds cool!
> >Instead of coding a complex parser it would be a good idea
> to store in
> >eeprom some commands like you explained. To do 'If ((Var1 &
> >Var2)&(Var3<0x0C))' I will store in eeprom something like:
>
> Yes, the parsing could be done off-line on a PC and a
> simulated stack machine could be coded on the PIC using
> bytecodes/tokens stored in the EEPROM. I've done this (not
> with a PIC, but it's no different).
>
> Best regards,
>
> Spehro Pefhany --"it's the network..."            "The
> Journey is the reward"
> speff@interlog.com             Info for manufacturers:
http://www.trexon.com
Embedded software/hardware/analog  Info for designers:
http://www.speff.com

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