Operators are just methods

overwrite_subtract.rb

# Operators are just methods. We can define and overwrite them just like any other.
# By operators I mean things like +, -, *, /, and the list goes on. But these
# are the most common.
#
# The goal for this program is to overwrite the subtract
# method. For RightTriangle. The result should be a RightTriangle whose sides
# are the result of performing subtraction (I know that's weird wording).




RightTriangle = Struct.new(:leg1, :leg2, :hypotenuse) do
  # Overwrite - method
  def -(right_triangle)
    # Return a smaller RightTriangle
    RightTriangle.new(self.leg1 - right_triangle.leg1, self.leg2 - right_triangle.leg2)
  end
end

# Pythagoras stays the same
class Pythagoras
  def self.theorem(right_triangle)
    hypotenuse = Math.sqrt((right_triangle.leg1 ** 2) + (right_triangle.leg2 ** 2))
    right_triangle.hypotenuse = hypotenuse
  end
end

r = RightTriangle.new(3, 4)
r2 = RightTriangle.new(1, 2)

# Using our new method. This is the same as doing r - r2. Ruby implements what's
# known as "syntactic sugar" that enables us to do things like this more elegantly.
# Below is the dot notation for calling methods that we've been using all along.
new_triangle = r.-(r2)

Pythagoras.theorem(r)
Pythagoras.theorem(r2)
Pythagoras.theorem(new_triangle)

p new_triangle

p new_triangle.hypotenuse