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From: dxf <dxforth@gmail.com>
Newsgroups: comp.lang.forth
Subject: Re: Parsing timestamps?
Date: Wed, 30 Oct 2024 11:31:10 +1100
Organization: i2pn2 (i2pn.org)
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On 30/10/2024 12:45 am, Hans Bezemer wrote:
> On 29-10-2024 10:25, dxf wrote:
>> On 29/10/2024 4:07 am, Hans Bezemer wrote:
>>> ...
>>> I have put the complication elsewhere. If we assume we're working in decimal, you don't even need >NUMBER:
>>>
>>> char 0 negate +constant 0-
>>>
>>> : /int    ( a1 n1 -- a2 n2 n3)
>>>    0 >r 1 >r 1- chars over +
>>>    begin
>>>     over 1- over <
>>>    while
>>>      dup c@ is-digit
>>>    while
>>>      dup c@ 0- r> tuck * r> + >r 10 * >r 1-
>>>    repeat over - rdrop r> -rot
>>> ;
>>> ...
>>
>> So that's how to convert a numeric string from the other end.
>> Nice!  Easier than I imagined it would be.
> 
> TORS is the multiplier, 2ORS is the accumulator. Normally, the multiplier is multiplied after each run with BASE @ - but that makes little sense when IS-DIGIT isn't properly adjusted. Would be a nice exercise, though.

Something like this...

\  \CHAR ( a u -- a u-1 c )
\  >DIGIT ( c base -- u -1 | c 0 )

: /INT ( a1 n1 -- a2 n2 u )                                     
  0 >r  1  begin  >r  dup while                                 
    \char  base @ >digit  while                                    
    r> tuck  *  r> + >r  base @ *                                  
  repeat  drop ( -1 /string)  then  rdrop  r> ;

OTOH the necessity to convert R-L is probably rare.