#palindrome checker
def is_palindrome?(number)
    number == number.to_s.reverse.to_i
end


#primes will consists of all primes starting with 2
#i will be incrememented and each i will be checked for being prime
primes = [2]
i = 3

#we only want the first 100 palindromic primes
while primes.length < 100
    #test is false for a prime
    test = false
    #checks if i is divisible by any of the elements in the array
    primes.each { |n|
        if i % n == 0
            test = true
        end
    }
    #if i is prime that it is added to the primes array
    if test == false
        primes.push(i)
    end
    i += 1
end

#remove all non palindromic primes
primes.each { |n|
    if is_palindrome?(n) == false
        primes.delete(n)
    end
}

#puts palindromic primes
puts primes

#palindrome checker
def is_palindrome?(number)
    number == number.to_s.reverse.to_i
end


#primes will consists of all primes starting with 2
#i will be incrememented and each i will be checked for being prime
primes = [2]
i = 3

#we only want the first 100 palindromic primes
while primes.length < 100
    #test is false for a prime
    test = false
    #checks if i is divisible by any of the elements in the array
    primes.each { |n|
        if i % n == 0
            test = true
        end
    }
    #if i is prime that it is added to the primes array
    if test == false
        primes.push(i) if is_palindrome?(i) # This is the line I changed
    end
    i += 1
end


#puts palindromic primes
puts primes

require 'prime'

is_palindrome = -> i { i.to_s == i.to_s.reverse }
puts Prime.lazy.select(&is_palindrome).take(100).to_a

# 2
# 3
# 5
# 7
# 11
# 101
# 131
# 151
# 181
# 191
# 313
# 353
# 373
# 383
# 727
# 757
# 787
# 797
# 919
# 929
# 10301
# 10501
# 10601
# 11311
# 11411
# 12421
# 12721
# 12821
# 13331
# 13831
# 13931
# 14341
# 14741
# 15451
# 15551
# 16061
# 16361
# 16561
# 16661
# 17471
# 17971
# 18181
# 18481
# 19391
# 19891
# 19991
# 30103
# 30203
# 30403
# 30703
# 30803
# 31013
# 31513
# 32323
# 32423
# 33533
# 34543
# 34843
# 35053
# 35153
# 35353
# 35753
# 36263
# 36563
# 37273
# 37573
# 38083
# 38183
# 38783
# 39293
# 70207
# 70507
# 70607
# 71317
# 71917
# 72227
# 72727
# 73037
# 73237
# 73637
# 74047
# 74747
# 75557
# 76367
# 76667
# 77377
# 77477
# 77977
# 78487
# 78787
# 78887
# 79397
# 79697
# 79997
# 90709
# 91019
# 93139
# 93239
# 93739
# 94049

primes.each { |n|
    if is_palindrome?(n) == false
        primes.delete(n)
    end
}

primes.each { |n|
    if is_palindrome?(n)
      puts n
    end
}

>> arr = %w{John Paul George Ringo}
=> ["John", "Paul", "George", "Ringo"]
>> # Print each one out; delete if it contains "o"
>> arr.each {|e| puts e; arr.delete e if e =~ /o/}
John
George
=> ["Paul", "Ringo"]

primes.delete_if { |n| !is_palindrome?(n) }

#palindrome checker
def is_palindrome?(number)
  number == number.to_s.reverse.to_i
end


#primes will consists of all primes starting with 2
#i will be incrememented and each i will be checked for being prime
primes = [2]
i = 3

#we only want the first 100 palindromic primes
while primes.length < 100

  #checks if i is divisible by any of the elements in the array
  primes << i unless primes.any? { |n| i % n == 0 }

  i += 1
end

#remove all non palindromic primes
primes.delete_if { |n| is_palindrome?(n) == false }

#puts palindromic primes
puts primes

# >> 2
# >> 3
# >> 5
# >> 7
# >> 11
# >> 101
# >> 131
# >> 151
# >> 181
# >> 191
# >> 313
# >> 353
# >> 373
# >> 383

primes.delete_if { |n| !is_palindrome?(n) }

puts primes.select{ |n| n == n.to_s.reverse.to_i }

#primes will consists of all primes starting with 2
#i will be incrememented and each i will be checked for being prime
primes = [2]
i = 3

#we only want the first 100 palindromic primes
while primes.length < 100

  #checks if i is divisible by any of the elements in the array
  primes << i unless primes.any? { |n| i % n == 0 }

  i += 1
end

#puts palindromic primes
puts primes.select{ |n| n == n.to_s.reverse.to_i }

require 'prime'

e = Prime.each
100.times {begin i = e.next end until i.to_s == i.to_s.reverse; puts i}

2
3
5
7
11
101
131
151
181
191
313
353
373
383
727
...

e.class = Prime::EratosthenesGenerator

i = e.succ

is_palindrome = -> (i) { i.to_s == i.to_s.reverse }

def prime?(number)
  flag = true

  (2..number/2).each do |n|
    if (number%n) == 0
      flag = false
      break
    end
  end

 flag
end

palindromic_primes = -> (length) do
  2.upto(Float::INFINITY).lazy.select { |x| is_palindrome.call(x) && prime?(x)  }.first(length)
end

puts palindromic_primes.(5)

require 'prime'
p Prime.each.lazy.select{|x| x.to_s == x.to_s.reverse}.first(100)