48 lines
1.3 KiB
Factor
48 lines
1.3 KiB
Factor
! Copyright (C) 2009 Samuel Tardieu.
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! See http://factorcode.org/license.txt for BSD license.
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USING: kernel kernel.private locals math math.bitwise
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math.functions math.order math.ranges sequences
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sequences.private ;
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IN: math.primes.erato
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<PRIVATE
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CONSTANT: masks
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{ f 128 f f f f f 64 f f f 32 f 16 f f f 8 f 4 f f f 2 f f f f f 1 }
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: bit-pos ( n -- byte mask/f )
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{ fixnum } declare
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30 /mod masks nth-unsafe
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{ maybe{ fixnum } } declare ; inline
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: marked-unsafe? ( n sieve -- ? )
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[ bit-pos ] dip swap
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[ [ nth-unsafe ] [ mask zero? not ] bi* ] [ 2drop f ] if* ; inline
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: unmark ( n sieve -- )
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[ bit-pos swap ] dip pick
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[ [ swap unmask ] change-nth-unsafe ] [ 3drop ] if ; inline
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: upper-bound ( sieve -- n ) length 30 * 1 - ; inline
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:: unmark-multiples ( i upper sieve -- )
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i sieve marked-unsafe? [
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i sq upper i <range> [ sieve unmark ] each
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] when ; inline
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: init-sieve ( n -- sieve )
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30 /i 1 + [ 255 ] B{ } replicate-as ; inline
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PRIVATE>
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:: sieve ( n -- sieve )
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n integer>fixnum-strict init-sieve :> sieve
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sieve upper-bound >fixnum :> upper
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2 upper sqrt [a,b]
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[ upper sieve unmark-multiples ] each
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sieve ;
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: marked-prime? ( n sieve -- ? )
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2dup upper-bound 2 swap between? [ bounds-error ] unless
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over { 2 3 5 } member? [ 2drop t ] [ marked-unsafe? ] if ;
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