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Truncatable primes: Difference between revisions

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Truncatable primes (view source)

Revision as of 10:11, 13 April 2011

278 bytes removed ,  13 years ago
m
→‎{{header|Ruby}}: use Prime module from stdlib
(add Ruby)
m (→‎{{header|Ruby}}: use Prime module from stdlib)
Line 961:
n = trunc_func.call(n)
return true if n == 0
return false if not Prime.prime?(n)
end
end
 
#############
require 'prime'
def eratosthenes(n)
numsprimes = [0, 0] + Prime.each(2..n1_000_000).to_a.reverse
(2**2..n).step(2) {|m| nums[m] = 0}
(3..Math.sqrt(n).to_i).step(2) do |i|
if nums[i].nonzero?
(i**2..n).step(i) {|m| nums[m] = 0}
end
end
nums.find_all {|m| m.nonzero?}
end
 
def prime?(n)
$primes.include? n
end
 
#############
$primes = eratosthenes(1_000_000).reverse
 
p $primes.detect {|p| left_truncatable? p}
p $primes.detect {|p| right_truncatable? p}</lang>
 
returns
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