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  1. require "prime"
  2.  
  3. def truncatable?(prime)
  4.   string = prime.to_s
  5.   string.length.times do |index|
  6.     ltr = string[index..-1].to_i
  7.     rtl = string[0..-1 - index].to_i
  8.  
  9.     return false unless Prime.prime?(ltr)
  10.     return false unless Prime.prime?(rtl)
  11.   end
  12.  
  13.   true
  14. end
  15.  
  16. primes = Prime.each.lazy
  17.   .drop(4) # skip 2, 3, 5, 7
  18.   .select { |prime| truncatable?(prime) }
  19.   .take(11)
  20.   .force
  21.  
  22. puts primes
  23.  
Runtime error #stdin #stdout #stderr 0.02s 7696KB
comments (?)
stdin 
Standard input is empty
stdout 
Standard output is empty
stderr 
prog.rb:17:in `<main>': undefined method `lazy' for #<Prime::EratosthenesGenerator:0x8775198> (NoMethodError)
https://ideone.com/gKxHcm
language:
Ruby (ruby 2.5.5)
created:
10 years ago
visibility:
public

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