openbios/fcode-utils/toke/examples/primes.fs

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• Hash : 837b7737
  Author :
  Date : 2006-08-18T09:07:34
  

  moving fcode suite to an extra directory git-svn-id: svn://coreboot.org/openbios/fcode-utils@74 f158a5a8-5612-0410-a976-696ce0be7e32

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• toke/examples/primes.fs

• \ primes.4th
  
  fcode-version2
  
  \ Example code for kForth
  \ Copyright (c) 1998 Creative Consulting for Research and Education
  \
  \ This program is free software; you may redistribute it under the terms of
  \ the GNU General Public License.  This program has absolutely no warranty.
  
  
  \ Test for a prime number. Return the largest divisor (< n ) 
  \ and a flag indicating whether the number is prime or not.
  
  : ?prime ( n -- m flag | is n a prime number? )
  \ if flag is false (0), m is the largest divisor of n
      abs
      dup 3 >		\ is n > 3 ?
      if
        dup 2 /mod
        swap 0= 
        if		\ is n divisible by 2 ?
          nip false
        else
          1-		\ check for divisibility starting	  
          begin		\ with n/2 - 1 and counting down
            2dup mod
            over 1 >
            and
          while
            1-
          repeat
          nip
          dup 1 <=
        then 
      else
        drop 1 true 
      then
  ;
  
  : test_prime ( n -- | test for prime number and display result )
      ?prime
      if
        ." is a prime number" drop
      else
        ." is NOT prime. Its largest divisor is " .
      then
      cr
  ;
  
  : list_primes ( n -- | list all the prime numbers from 1 to n )
      abs
      dup 0>
      if 
        1+ 1 do
          i ?prime 
  	if i . cr then 
  	drop
        loop
      else
        drop
      then
  ;
   
  10000 list_primes
  
  fcode-end
  
  

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