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Groups > comp.lang.forth > #20427

Re: Reverse factorial

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Ed wrote:

> 15 set-precision
> 
> 1e9 fconstant #digits
> 
> : N! ( -- )
>   0.0e ( N)
>   0.0e ( A)
>   begin
>     fswap 1.0e f+ fswap
>     fover flog f+
>     fdup [ #digits 1.0e f- ] fliteral f< 0=
>   until
>   ( N A) fdrop f.
> ;
> 
> : run ( -- )
>   cr cr ." Smallest number with a factorial of at least "
>   #digits fs. ." digits is ... " cr n!
> ;
> 
> run
> 
> --
> 
> DX-Forth 3.98  2012-06-26
> 
> Forth-94
> 80387 15-digit floating point (common stack)
> 
> include n!
> 
> Smallest number with a factorial of at least 1.E9 digits is ...
> 130202809.  ok

Factor:

USING: locals math.functions ;

CONSTANT: #digits 1e9

:: N! ( -- )
  0.0 :> n!
  0.0 :> a!
  [ n 1.0 +  n!
    a n log10 +  a!
    a #digits 1.0 - <
  ]
  loop
  n .
;

N!
130202809.0

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Reverse factorial "Ed" <invalid@nospam.com> - 2012-06-29 11:51 +1000
  Re: Reverse factorial mhx@iae.nl (Marcel Hendrix) - 2012-06-30 02:05 +0200
    Re: Reverse factorial "Ed" <invalid@nospam.com> - 2012-06-30 12:26 +1000
    Re: Reverse factorial "Ed" <invalid@nospam.com> - 2012-07-01 23:17 +1000
      Re: Reverse factorial mhx@iae.nl (Marcel Hendrix) - 2012-07-01 16:51 +0200
        Re: Reverse factorial "Ed" <invalid@nospam.com> - 2012-07-02 05:40 +1000
          Re: Reverse factorial Paul Rubin <no.email@nospam.invalid> - 2012-07-02 22:08 -0700
            Re: Reverse factorial "Ed" <invalid@nospam.com> - 2012-07-03 17:02 +1000
            Re: Reverse factorial mhx@iae.nl (Marcel Hendrix) - 2012-07-03 21:14 +0200
              Re: Reverse factorial Paul Rubin <no.email@nospam.invalid> - 2012-07-03 12:44 -0700
                Re: Reverse factorial mhx@iae.nl (Marcel Hendrix) - 2012-07-03 22:37 +0200
                Re: Reverse factorial "Ed" <invalid@nospam.com> - 2012-07-05 23:14 +1000
  Re: Reverse factorial "WJ" <w_a_x_man@yahoo.com> - 2013-03-08 09:14 +0000

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