Triangle Classification Lab

Learning Goals

• Define a custom error class and use it

Instructions

Write a Triangle class that accepts three arguments on initialization. Each argument is a length of one of the three sides of the triangle.

Define an instance method, #kind that returns, as a symbol, its type. The valid types are:

• :equilateral
• :isosceles
• :scalene

The #kind method should raise a custom error, TriangleError if the triangle is invalid. Check out the hint below to understand what makes a triangle valid.

Write a custom error class, TriangleError and inherit it from StandardError. This custom error class should be defined in the same file as the Triangle class, inside the Triangle class definition, like this:

# lib/triangle.rb

class Triangle
  # triangle code

  class TriangleError < StandardError
    # triangle error code
  end
end

Note: Several of the tests will be looking for the TriangleError to be raised. If you implement a rescue for it, however, the tests will not recognize that the error was raised. For purposes of this lab, therefore, you should not include a rescue.

Identifying Valid Triangles

A valid triangle must meet the following criteria:

• Each side must be larger than 0.

• The sum of the lengths of any two sides of a triangle always exceeds the length of the third side. This is a principle known as the triangle inequality.

Resources

• Exception Handling
• Basic Mathematics - Types of Triangles