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Re: Rosetta code binomial coefficient

Newsgroups comp.lang.forth
Date 2015-11-06 23:24 -0800
References <4fa62f0c-dab1-4bc0-bbda-8c250a6955d4@googlegroups.com>
Message-ID <ee23c48f-c19b-460e-89cd-34443ae08512@googlegroups.com> (permalink)
Subject Re: Rosetta code binomial coefficient
From mhx@iae.nl

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On Saturday, November 7, 2015 at 7:05:04 AM UTC+1, krishna...@ccreweb.org wrote:
> The Forth entry on Rosetta Code for computing the binomial
> coefficient is beautiful. Compare its compactness of 
> implementation with those in other languages. This is 
> a very nice code example in Forth. Although it meets 
> the requirements of the entry, single integers for 32 
> bit word size quickly lead to failure, e.g. "60 30 
> choose". The implementation is better suited for 64-bit 
> word size.
> 
> : choose ( n k -- nCk ) 1 swap 0 ?do over i - i 1+ */ loop nip ;
> 
> Good job, whoever submitted this to Rosetta Code!

This algorithm must be quite common, in Forth or elsewhere --
I have it in Euler158.frt (2008) as 

: binomial ( n k -- d )
	LOCALS| k n |
	1  k 1+ 1 DO  n I - 1+  I */  LOOP ; 

In Euler113.frt (2008) it is defined using arbitrary precision:

-- result in binom
: binomial ( n k -- binom )
	LOCALS| k n |
	1 binom V!
	k 1+ 1 DO  binom  n I - 1+ VS*
		   binom  I VS/MOD DROP  
	     LOOP 
	binom ; PRIVATE

-marcel

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Thread

Rosetta code binomial coefficient krishna.myneni@ccreweb.org - 2015-11-06 22:05 -0800
  Re: Rosetta code binomial coefficient mhx@iae.nl - 2015-11-06 23:24 -0800
    Re: Rosetta code binomial coefficient Albert van der Horst <albert@spenarnc.xs4all.nl> - 2015-11-07 10:58 +0000
  Re: Rosetta code binomial coefficient "WJ" <w_a_x_man@yahoo.com> - 2015-11-07 08:14 +0000
    Re: Rosetta code binomial coefficient "WJ" <w_a_x_man@yahoo.com> - 2015-11-07 14:05 +0000
      Re: Rosetta code binomial coefficient "WJ" <w_a_x_man@yahoo.com> - 2015-11-15 06:18 +0000
  Re: Rosetta code binomial coefficient Paul Rubin <no.email@nospam.invalid> - 2015-11-07 00:23 -0800
    Re: Rosetta code binomial coefficient Bernd Paysan <bernd.paysan@gmx.de> - 2015-11-07 15:11 +0100
      Re: Rosetta code binomial coefficient krishna.myneni@ccreweb.org - 2015-11-07 07:49 -0800
      Re: Rosetta code binomial coefficient krishna.myneni@ccreweb.org - 2015-11-07 08:10 -0800
      Re: Rosetta code binomial coefficient Paul Rubin <no.email@nospam.invalid> - 2015-11-07 08:50 -0800
        Re: Rosetta code binomial coefficient Bernd Paysan <bernd.paysan@gmx.de> - 2015-11-07 20:20 +0100
          Re: Rosetta code binomial coefficient krishna.myneni@ccreweb.org - 2015-11-07 17:45 -0800
          Re: Rosetta code binomial coefficient Paul Rubin <no.email@nospam.invalid> - 2015-11-07 19:50 -0800
            Re: Rosetta code binomial coefficient "WJ" <w_a_x_man@yahoo.com> - 2015-11-08 15:35 +0000
              Re: Rosetta code binomial coefficient "WJ" <w_a_x_man@yahoo.com> - 2015-11-25 20:29 +0000
                Re: Rosetta code binomial coefficient Paul Rubin <no.email@nospam.invalid> - 2015-11-25 12:43 -0800
            Re: Rosetta code binomial coefficient Bernd Paysan <bernd.paysan@gmx.de> - 2015-11-08 18:51 +0100
              Re: Rosetta code binomial coefficient Albert van der Horst <albert@spenarnc.xs4all.nl> - 2015-11-08 18:51 +0000
              Re: Rosetta code binomial coefficient Paul Rubin <no.email@nospam.invalid> - 2015-11-08 19:55 -0800
  Re: Rosetta code binomial coefficient krishna.myneni@ccreweb.org - 2015-11-08 07:03 -0800
  Re: Rosetta code binomial coefficient krishna.myneni@ccreweb.org - 2015-11-09 06:57 -0800
    Re: Rosetta code binomial coefficient krishna.myneni@ccreweb.org - 2015-11-10 03:49 -0800
      Re: Rosetta code binomial coefficient Ron Aaron <rambamist@gmail.com> - 2015-11-10 14:01 +0200
        Re: Rosetta code binomial coefficient krishna.myneni@ccreweb.org - 2015-11-10 19:13 -0800
          Re: Rosetta code binomial coefficient Ron Aaron <rambamist@gmail.com> - 2015-11-11 07:38 +0200
  Re: Rosetta code binomial coefficient glidedog@gmail.com - 2015-11-14 05:26 -0800
    Re: Rosetta code binomial coefficient krishna.myneni@ccreweb.org - 2015-11-14 06:19 -0800
      Re: Rosetta code binomial coefficient krishna.myneni@ccreweb.org - 2015-11-14 06:22 -0800
      Re: Rosetta code binomial coefficient glidedog@gmail.com - 2015-11-14 08:16 -0800
        Re: Rosetta code binomial coefficient krishna.myneni@ccreweb.org - 2015-11-14 11:16 -0800
  Re: Rosetta code binomial coefficient "WJ" <w_a_x_man@yahoo.com> - 2016-06-28 00:02 +0000

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