Ruby Quiz #6: Too Simple?

Matt Secoske and I were pairing last night and we decided to work on quiz #6 from the Ruby Quiz book. Here's our code complete with tests.

require 'test/unit'
require 'test/unit/ui/console/testrunner'

module Enumerable
  def in?(candidate)
    any? {|any| any.in? candidate}
  end
end


class Fixnum
  def in?(candidate)
    equal? candidate
  end
end


class Range
  def in?(candidate)
    include? candidate
  end
end


class BuildRegexp
  GUARD = /^[0123456789]+$/
  
  def initialize(candidates)
    @candidates = candidates
  end
  
  def =~(candidate)
    GUARD =~ candidate && (@candidates.in? candidate.to_i)
  end
end

class Regexp
  def self.build(*candidates)
    BuildRegexp.new(candidates)
  end
  
end


class BuildTest < Test::Unit::TestCase
  def test_lucky()
    lucky = Regexp.build(3,7)
    assert('7' =~ lucky)
    assert(!('13' =~ lucky))
    assert('3' =~ lucky)
  end
  
  def test_month()
    month = Regexp.build(1..12)
    assert(!('0' =~ month))
    assert('1' =~ month)
    assert('12' =~ month)
  end
  
  def test_day()
    day = Regexp.build(1..31)
    assert('6' =~ day)
    assert('16' =~ day)
    assert(!('Tues' =~ day))
  end
  
  def test_year()
    year = Regexp.build(98,99,2000..2005)
    assert(!('04' =~ year))
    assert('2004' =~ year)
    assert('98' =~ year)
  end
  
  def test_num()
    num = Regexp.build(0..1_000_000)
    assert(!('-1' =~ num))
  end
  
end

Test::Unit::UI::Console::TestRunner.new(BuildTest.suite()).start()

Of course, we excitedly looked up the answer in the book and were shocked. Their final answer was longer and harder to understand. Our code uses less of the regular expression class. In fact, we only used it as a guard to make sure we could convert the input to a number. We also made heavy use of polymorphism and duck typing(in?, =~). As you can see the code is very short.

The quiz was to build a Regexp to handle any list or range of numbers. The tests are taken exactly from the book and of course, we wrote them first. Well, actually, we wrote them at each stage. At one point, we were using Regexp extensively until we hit the last test. And that is when the change in requirements caused all of the code you see above.

How fun! We looked at each other and wondered, "Was our solution too simple?" We then laughed and said, "Nah." We were both proud for our simple and readable solution.