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Message from discussion RTX2000 optimization
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Bernd Paysan  
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 More options Nov 4 2012, 12:41 pm
Newsgroups: comp.lang.forth
From: Bernd Paysan <bernd.pay...@gmx.de>
Date: Sun, 04 Nov 2012 18:40:57 +0100
Local: Sun, Nov 4 2012 12:40 pm
Subject: Re: RTX2000 optimization
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Marcel Hendrix wrote:
> The online version is around 35 lines, so I am really curious how
> Bernd got less than 16. Also, the online version does not work
> 'in reverse' and can't use HOLD, so I guess it was reworked.
> Below is my take.

That was my take on it (the timestamp is my last change to it which was
using <<# #> #>> nestable pictured numeric output):

\ roman numbers                                        07aug10py

Variable column#
: symbol ( off -- ) column# @ + s" IVXLCDM  " drop +  c@ hold ;
: oner   ( -- )    0  symbol ;
: fiver  ( -- )    1  symbol ;
: almost ( q -- )  1+ symbol  oner ;

: oners  ( n -- )  0 ?DO  oner  LOOP ;
: digit ( digit -- )  5 /mod over 4 =  IF  almost drop
  ELSE  swap oners  IF  fiver  THEN  THEN ;
: #r  ( digit -- digit' )  10 /mod swap  digit  2 column# +! ;
: roman ( number -- )
  column# off  <<# #r #r #r #r 0 #>  type #>> ;

This is slightly overfactored, so if you just want to have a low number
of lines, it becomes:

Variable column#
: symbol ( off -- ) column# @ + s" IVXLCDM  " drop +  c@ hold ;
: digit ( digit -- )  5 /mod over 4 =  IF  1+ symbol 0 symbol drop
  ELSE  swap 0 ?DO 0 symbol LOOP  IF  1 symbol  THEN  THEN ;
: #r  ( digit -- digit' )  10 /mod swap  digit  2 column# +! ;
: roman ( number -- )
  column# off  <<# #r #r #r #r 0 #>  type #>> ;

--
Bernd Paysan
"If you want it done right, you have to do it yourself"
http://bernd-paysan.de/


 
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