triangle.rb

# Triangle Project Code.

# Triangle analyzes the lengths of the sides of a triangle
# (represented by a, b and c) and returns the type of triangle.
#
# It returns:
#   :equilateral  if all sides are equal
#   :isosceles    if exactly 2 sides are equal
#   :scalene      if no sides are equal
#
# The tests for this method can be found in
#   about_triangle_project.rb
# and
#   about_triangle_project_2.rb
#
require 'set'

def triangle(a, b, c)
  sides = Set.new [a, b, c]
  
  raise TriangleError if sides.any? { |s| s == 0 or s < 0 }
  fake_triangle = [[a + b, c], [a + c, b], [b + c, a]].any? { |x| x.first <= x.last }
  raise TriangleError if fake_triangle
  
  triangles = {1 => :equilateral, 2 => :isosceles, 3 => :scalene }
  return triangles[sides.length]
end

# Error class used in part 2.  No need to change this code.
class TriangleError < StandardError
end