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From: melahi_ahmed@yahoo.fr (Ahmed)
Newsgroups: comp.lang.forth
Subject: Re: exercise in double number arithmetic
Date: Sun, 7 Jul 2024 16:13:33 +0000
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On Sun, 7 Jul 2024 15:41:54 (UTC), mhx wrote:

> On Sun, 7 Jul 2024 11:24:35 (UTC), albert@spenarnc.xs4all.nl wrote:
>
>>>How many different ways can you choose 42 distinct objects, 21 at a
>>>time? This is "n choose k" or the binomial coefficent.
>>>
>>>Please show your code.
> [..]
>>  2 \ For N M return "N OVER M " (N/M)
>>  3 : CHS >R  R@ - 1 R> 1+ 1 ?DO   OVER I + I */ LOOP NIP ;
> [..]
>
> Really great!
>
> FORTH> 42 21 CHS . 538257874440  ok
> FORTH> 66 33 CHS . 7219428434016265740  ok
> FORTH> 68 34 CHS . ( ... )
>
> -marcel


Hi,

100 value N

create table N N * 2* cells allot


table N N * 2* cells erase
: table.init N 0 do 1. table i N * 2* cells + 2! loop ;
table.init
: table.calc N 1 do N 1 do table j 1 -   N * i 1 - + 2* cells + 2@
                             table j 1 - N * i     + 2* cells + 2@ d+
                             table j     N * i     + 2* cells + 2!
loop loop ;
table.calc

table 68 N * 34 + 2* cells + 2@ d.  28453041475240576740  ok

Wolfram alpha gives C(68,43) = 28453041475240576740


minforth version gives: 68 34 bcoef  28453041475240574976  ok (it is
different)


Ahmed