Re: exercise in double number arithmetic

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