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Forth200x enhanced locals implementation

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The proposal for the Forth200x enhanced locals proposal does not
contain a portable implementation, even though implementing the syntax
is possible portably (increasing the number of locals, also contained
in that proposal, requires carnal knowledge).

So I implemented the X:locals syntax portably, and you can find the
result in compat/xlocals.fs in
<http://www.complang.tuwien.ac.at/forth/compat.zip>.

There is an interesting insight in this implementation: I started out
with the <http://www.complang.tuwien.ac.at/forth/anslocal.fs> code
inspired by John Hayes' paper on implementing the { ... } syntax and
added the "|" option and some error checking.

The interesting change is that I switched from BL WORD COUNT to using
PARSE-NAME.  This significantly simplified the implementation, as I
did not need to save and restore >IN, and reparse each local, but
could just keep the parsed string descriptors around.

The central words in the implementations are:

\ old                                \ new
: {helper ( -- final-offset )        : {helper ( f "name1"..."namen" -- ) 
  >in @                                parse-name1                        
  bl word count                        2dup s" |" compare 0= if           
  2dup s" --" compare 0= if              2drop drop true parse-name1 then 
    2drop [char] } parse 2drop true    2dup s" --" compare 0= if          
  else                                   2drop drop parse-rest exit then  
    s" }" compare 0=                   2dup s" :}" compare 0= if          
  then                                   2drop drop exit then             
  if                                   rot dup if \ we are in the | part  
    drop >in @                           0 postpone literal then          
  else                                 recurse (local) ;                  
    recurse
    swap >in ! local
  then ;

- anton
-- 
M. Anton Ertl  http://www.complang.tuwien.ac.at/anton/home.html
comp.lang.forth FAQs: http://www.complang.tuwien.ac.at/forth/faq/toc.html
     New standard: http://www.forth200x.org/forth200x.html
   EuroForth 2013: http://www.euroforth.org/ef13/

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Forth200x enhanced locals implementation anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-10-30 17:03 +0000
  Re: Forth200x enhanced locals implementation "Alex McDonald" <blog@rivadpm.com> - 2013-10-30 22:23 +0000
    Re: Forth200x enhanced locals implementation anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-10-31 12:06 +0000
      Re: Forth200x enhanced locals implementation "Alex McDonald" <blog@rivadpm.com> - 2013-10-31 18:01 +0000
        Re: Forth200x enhanced locals implementation anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-11-01 08:46 +0000
          Re: Forth200x enhanced locals implementation "Alex McDonald" <blog@rivadpm.com> - 2013-11-01 10:36 +0000
  Re: Forth200x enhanced locals implementation albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-10-31 14:21 +0000
  Re: Forth200x enhanced locals implementation anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-11-03 14:22 +0000

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