Given a year, report if it is a leap year.
The tricky thing here is that a leap year in the Gregorian calendar occurs:
on every year that is evenly divisible by 4 except every year that is evenly divisible by 100 unless the year is also evenly divisible by 400
For example, 1997 is not a leap year, but 1996 is. 1900 is not a leap year, but 2000 is.
If your language provides a method in the standard library that does this look-up, pretend it doesn't exist and implement it yourself.
Though our exercise adopts some very simple rules, there is more to learn!
For a delightful, four minute explanation of the whole leap year phenomenon, go watch this youtube video.
For installation and learning resources, refer to the exercism help page.
For running the tests provided, you will need the Minitest gem. Open a terminal window and run the following command to install minitest:
gem install minitest
If you would like color output, you can
require 'minitest/pride' in
the test file, or note the alternative instruction, below, for running
the test file.
Run the tests from the exercise directory using the following command:
To include color from the command line:
ruby -r minitest/pride leap_test.rb
JavaRanch Cattle Drive, exercise 3 http://www.javaranch.com/leap.jsp
It's possible to submit an incomplete solution so you can see how others have completed the exercise.
require 'minitest/autorun' require_relative 'leap' # Common test data version: 1.1.0 7f4d0d8 class Date def leap? raise RuntimeError, "Implement this yourself instead of using Ruby's implementation." end alias gregorian_leap? leap? alias julian_leap? leap? end class YearTest < Minitest::Test def test_year_not_divisible_by_4_common_year # skip refute Year.leap?(2015), "Expected 'false', 2015 is not a leap year." end def test_year_divisible_by_4_not_divisible_by_100_leap_year skip assert Year.leap?(2020), "Expected 'true', 2020 is a leap year." end def test_year_divisible_by_100_not_divisible_by_400_common_year skip refute Year.leap?(2100), "Expected 'false', 2100 is not a leap year." end def test_year_divisible_by_400_leap_year skip assert Year.leap?(2000), "Expected 'true', 2000 is a leap year." end # Problems in exercism evolve over time, as we find better ways to ask # questions. # The version number refers to the version of the problem you solved, # not your solution. # # Define a constant named VERSION inside of the top level BookKeeping # module, which may be placed near the end of your file. # # In your file, it will look like this: # # module BookKeeping # VERSION = 1 # Where the version number matches the one in the test. # end # # If you are curious, read more about constants on RubyDoc: # http://ruby-doc.org/docs/ruby-doc-bundle/UsersGuide/rg/constants.html def test_bookkeeping skip assert_equal 3, BookKeeping::VERSION end end
class Year VERSION = 1 YEARS_TO_LOSE_ONE_SOLAR_DAY = 4 CENTURIES_TO_GAIN_THREE_SOLAR_DAYS = 4 CENTURY = 100 class << self def leap?(year) account_for_one_day_lost?(year) && !account_for_three_days_gained?(year) end private def account_for_one_day_lost?(year) year % YEARS_TO_LOSE_ONE_SOLAR_DAY == 0 end def account_for_three_days_gained?(year) year % CENTURY == 0 && year % (CENTURIES_TO_GAIN_THREE_SOLAR_DAYS * CENTURY) != 0 end end end
A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.
Here are some questions to help you reflect on this solution and learn the most from it.