Tests a regular expression for recognising binary numbers that are divisible by 3.

three_test.rb

your_re = // # <= YOUR REGEX GOES BETWEEN THESE SLASHES*************************
#Example: /.*/
# This wraps your regex so the whole binary string has to match it
@re = /^(#{your_re})$/

# Helper code to convert numbers to binary strings
class Fixnum
  def to_bin_s
    return '0' if self == 0
    s = ''
    n = self

    while n > 0
      s = (n % 2).to_s << s
      n = n >> 1
    end
    s
  end
end

def test(limit)
  incorrect = {:neg => [], :pos => []}
  limit.times do |n|
    multiple_of_3 = n%3 == 0
    incorrect[:pos] << n if @re.match(n.to_bin_s) and !multiple_of_3
    incorrect[:neg] << n if !@re.match(n.to_bin_s) and multiple_of_3
  end
  passed = (incorrect[:pos].empty? and incorrect[:neg].empty?)
  passed ? 'Pass =]' : incorrect
end

result = test 50 # <= INCREASE THIS NUMBER TO RUN FOR MORE CASES****************

# Print the results
puts result unless result.class == {}.class
if result.class == {}.class
  puts "\nFalse Positives:"
  print_bin = lambda {|n| print "  #{n.to_bin_s}" }
  result[:pos].each &print_bin
  puts "\n\nFalse Negatives:"
  result[:neg].each &print_bin
  puts "\n\nTotal: #{result[:neg].length + result[:pos].length}"
end