methods

# Methods: functions that belong to a type.

struct Rectangle
  getter width : Float64
  getter height : Float64

  def initialize(@width : Float64, @height : Float64)
  end

  def area : Float64
    width * height
  end

  def square? : Bool
    width == height
  end

  # A method can take arguments like any function.
  def scale(factor : Float64) : Rectangle
    Rectangle.new(width * factor, height * factor)
  end
end

r = Rectangle.new(3.0, 4.0)
puts r.area
puts r.square?
puts r.scale(2.0).area

# Methods on the built-in types work the same way.
puts "iyi".upcase
puts 3.7.round
puts [1, 2, 3].sum