ruby - triangle

ruby/triangle/README.md

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+# Triangle
+
+Determine if a triangle is equilateral, isosceles, or scalene.
+
+An _equilateral_ triangle has all three sides the same length.
+
+An _isosceles_ triangle has at least two sides the same length. (It is sometimes
+specified as having exactly two sides the same length, but for the purposes of
+this exercise we'll say at least two.)
+
+A _scalene_ triangle has all sides of different lengths.
+
+## Note
+
+For a shape to be a triangle at all, all sides have to be of length > 0, and
+the sum of the lengths of any two sides must be greater than or equal to the
+length of the third side. See [Triangle Inequality](https://en.wikipedia.org/wiki/Triangle_inequality).
+
+## Dig Deeper
+
+The case where the sum of the lengths of two sides _equals_ that of the
+third is known as a _degenerate_ triangle - it has zero area and looks like
+a single line. Feel free to add your own code/tests to check for degenerate triangles.
+
+* * * *
+
+For installation and learning resources, refer to the
+[Ruby resources page](http://exercism.io/languages/ruby/resources).
+
+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:
+
+    ruby triangle_test.rb
+
+To include color from the command line:
+
+    ruby -r minitest/pride triangle_test.rb
+
+
+## Source
+
+The Ruby Koans triangle project, parts 1 & 2 [http://rubykoans.com](http://rubykoans.com)
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.

ruby/triangle/triangle.rb

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+# Triangle class
+class Triangle
+  def initialize(sides)
+    @sides = sides.sort
+  end
+
+  def equilateral?
+    @sides.uniq.length == 1 && triangle_equality?
+  end
+
+  def isosceles?
+    @sides.uniq.length < 3 && triangle_equality?
+  end
+
+  def scalene?
+    @sides.uniq.length == 3 && triangle_equality?
+  end
+
+  private
+
+  def triangle_equality?
+    @sides.min > 0 && @sides[0] + @sides[1] >= @sides[2]
+  end
+end

ruby/triangle/triangle_test.rb

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+require 'minitest/autorun'
+require_relative 'triangle'
+
+# Common test data version: 1.2.0 55f89ca
+class TriangleTest < Minitest::Test
+  def test_triangle_is_equilateral_if_all_sides_are_equal
+    # skip
+    triangle = Triangle.new([2, 2, 2])
+    assert triangle.equilateral?, "Expected 'true', triangle [2, 2, 2] is equilateral."
+  end
+
+  def test_triangle_is_not_equilateral_if_any_side_is_unequal
+    # skip
+    triangle = Triangle.new([2, 3, 2])
+    refute triangle.equilateral?, "Expected 'false', triangle [2, 3, 2] is not equilateral."
+  end
+
+  def test_triangle_is_not_equilateral_if_no_sides_are_equal
+    # skip
+    triangle = Triangle.new([5, 4, 6])
+    refute triangle.equilateral?, "Expected 'false', triangle [5, 4, 6] is not equilateral."
+  end
+
+  def test_all_zero_sides_are_illegal_so_the_triangle_is_not_equilateral
+    # skip
+    triangle = Triangle.new([0, 0, 0])
+    refute triangle.equilateral?, "Expected 'false', triangle [0, 0, 0] is not equilateral."
+  end
+
+  def test_equilateral_triangle_sides_may_be_floats
+    # skip
+    triangle = Triangle.new([0.5, 0.5, 0.5])
+    assert triangle.equilateral?, "Expected 'true', triangle [0.5, 0.5, 0.5] is equilateral."
+  end
+
+  def test_triangle_is_isosceles_if_last_two_sides_are_equal
+    # skip
+    triangle = Triangle.new([3, 4, 4])
+    assert triangle.isosceles?, "Expected 'true', triangle [3, 4, 4] is isosceles."
+  end
+
+  def test_triangle_is_isosceles_if_first_two_sides_are_equal
+    # skip
+    triangle = Triangle.new([4, 4, 3])
+    assert triangle.isosceles?, "Expected 'true', triangle [4, 4, 3] is isosceles."
+  end
+
+  def test_triangle_is_isosceles_if_first_and_last_sides_are_equal
+    # skip
+    triangle = Triangle.new([4, 3, 4])
+    assert triangle.isosceles?, "Expected 'true', triangle [4, 3, 4] is isosceles."
+  end
+
+  def test_equilateral_triangles_are_also_isosceles
+    # skip
+    triangle = Triangle.new([4, 4, 4])
+    assert triangle.isosceles?, "Expected 'true', triangle [4, 4, 4] is isosceles."
+  end
+
+  def test_triangle_is_not_isosceles_if_no_sides_are_equal
+    # skip
+    triangle = Triangle.new([2, 3, 4])
+    refute triangle.isosceles?, "Expected 'false', triangle [2, 3, 4] is not isosceles."
+  end
+
+  def test_sides_that_violate_triangle_inequality_are_not_isosceles_even_if_two_are_equal_1
+    # skip
+    triangle = Triangle.new([1, 1, 3])
+    refute triangle.isosceles?, "Expected 'false', triangle [1, 1, 3] is not isosceles."
+  end
+
+  def test_sides_that_violate_triangle_inequality_are_not_isosceles_even_if_two_are_equal_2
+    # skip
+    triangle = Triangle.new([1, 3, 1])
+    refute triangle.isosceles?, "Expected 'false', triangle [1, 3, 1] is not isosceles."
+  end
+
+  def test_sides_that_violate_triangle_inequality_are_not_isosceles_even_if_two_are_equal_3
+    # skip
+    triangle = Triangle.new([3, 1, 1])
+    refute triangle.isosceles?, "Expected 'false', triangle [3, 1, 1] is not isosceles."
+  end
+
+  def test_isosceles_triangle_sides_may_be_floats
+    # skip
+    triangle = Triangle.new([0.5, 0.4, 0.5])
+    assert triangle.isosceles?, "Expected 'true', triangle [0.5, 0.4, 0.5] is isosceles."
+  end
+
+  def test_triangle_is_scalene_if_no_sides_are_equal
+    # skip
+    triangle = Triangle.new([5, 4, 6])
+    assert triangle.scalene?, "Expected 'true', triangle [5, 4, 6] is scalene."
+  end
+
+  def test_triangle_is_not_scalene_if_all_sides_are_equal
+    # skip
+    triangle = Triangle.new([4, 4, 4])
+    refute triangle.scalene?, "Expected 'false', triangle [4, 4, 4] is not scalene."
+  end
+
+  def test_triangle_is_not_scalene_if_two_sides_are_equal
+    # skip
+    triangle = Triangle.new([4, 4, 3])
+    refute triangle.scalene?, "Expected 'false', triangle [4, 4, 3] is not scalene."
+  end
+
+  def test_sides_that_violate_triangle_inequality_are_not_scalene_even_if_they_are_all_different
+    # skip
+    triangle = Triangle.new([7, 3, 2])
+    refute triangle.scalene?, "Expected 'false', triangle [7, 3, 2] is not scalene."
+  end
+
+  def test_scalene_triangle_sides_may_be_floats
+    # skip
+    triangle = Triangle.new([0.5, 0.4, 0.6])
+    assert triangle.scalene?, "Expected 'true', triangle [0.5, 0.4, 0.6] is scalene."
+  end
+end