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sieve.fs
1 (* Copyright (c) 2009 the authors listed at the following URL, and/or 2 the authors of referenced articles or incorporated external code: 3 http://en.literateprograms.org/Sieve_of_Eratosthenes_(Forth)?action=history&offset=20070516000916 4 5 Permission is hereby granted, free of charge, to any person obtaining 6 a copy of this software and associated documentation files (the 7 "Software"), to deal in the Software without restriction, including 8 without limitation the rights to use, copy, modify, merge, publish, 9 distribute, sublicense, and/or sell copies of the Software, and to 10 permit persons to whom the Software is furnished to do so, subject to 11 the following conditions: 12 13 The above copyright notice and this permission notice shall be 14 included in all copies or substantial portions of the Software. 15 16 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 17 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 18 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 19 IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 20 CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, 21 TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE 22 SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 23 24 Retrieved from: http://en.literateprograms.org/Sieve_of_Eratosthenes_(Forth)?oldid=10096 25 *) 26 27 7919 2/ CONSTANT maxp \ 2/ because we only count odd primes 28 29 : PRIMES ( -- n ) 30 HERE maxp 1 FILL 31 1 ( count, including 2 ) 32 maxp 0 DO 33 I HERE + C@ IF 34 I 2* 3 + ( dup .) DUP I + ( prime current ) 35 BEGIN DUP maxp U< 36 WHILE 0 OVER HERE + C! 37 OVER + 38 REPEAT 39 2DROP 1+ 40 THEN 41 LOOP ; 42 43 PRIMES . \ 1000 44
