Leap Year Calculation with Lambdas

leap_year_spec.rb

#!/usr/bin/env rspec


def leap_year?(year)
  is_mult_of = ->(year, multiplier) { year % multiplier == 0 }
  return false unless is_mult_of.(year, 4)
  return true unless is_mult_of.(year, 100)
  return is_mult_of.(year, 400)
end


# This way is more verbose but might be clearer.
def leap_year_2?(year)
  fn_multiple_of = ->(multiplier) { ->(a_year) { a_year % multiplier == 0 } }
  mult_of_4   = fn_multiple_of.(4)
  mult_of_100 = fn_multiple_of.(100)
  mult_of_400 = fn_multiple_of.(400)

  return false unless mult_of_4.(year)
  return true unless mult_of_100.(year)
  return mult_of_400.(year)
  # mult_of_4.(year) && ((!mult_of_100.(year)) || (! mult_of_400.(year)))
end

describe 'leap_year?' do

  test_a_year = ->(year, expected_result) do
    specify "Year #{year} should return #{expected_result}" do
      leap_year?(year).should == expected_result
    end
  end

  test_a_year.(2000, true)
  test_a_year.(2001, false)
  test_a_year.(2004, true)
  test_a_year.(2100, false)
end