def method

def method cheatsheet

def method_name(x1,x2,x3,x4)
def method_name(name,mode ='r')
def method_name(options)
def method_name(*points)

def story2(options={})
 options = { person: "Yankee Doodle", animal: "Tiger" }.merge(options)
 "#{options[:person]} went to town, riding on a #{options[:animal]}"
end

def distance4(*points)
 x1,y1,x2,y2 = points.flatten
 raise ArgumentError unless [x1,y1,x2,y2].all? { |e| Numeric === e }
 Math.hypot(x2 - x1, y2 - y1)
end

"This is a string".instance_eval do
 "O hai, can has reverse? #{reverse}. kthxbye"
 end