30 lines
706 B
Factor
30 lines
706 B
Factor
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! Copyright (C) 2009 Doug Coleman.
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! See http://factorcode.org/license.txt for BSD license.
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USING: combinators.short-circuit kernel math math.functions
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math.primes random ;
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IN: math.primes.safe
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<PRIVATE
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: safe-prime-candidate? ( n -- ? )
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1 + 6 divisor? ;
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: next-safe-prime-candidate ( n -- candidate )
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next-prime dup safe-prime-candidate?
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[ next-safe-prime-candidate ] unless ;
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PRIVATE>
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: safe-prime? ( q -- ? )
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{
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[ 1 - 2 / dup integer? [ prime? ] [ drop f ] if ]
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[ prime? ]
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} 1&& ;
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: next-safe-prime ( n -- q )
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next-safe-prime-candidate
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dup safe-prime? [ next-safe-prime ] unless ;
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: random-safe-prime ( numbits -- p )
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random-bits* next-safe-prime ;
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