After more tinkering in Ruby, I came across the need to use the Stack data structure. To my surprise, one was nowhere to be found. However, I was even more surprised when I found out that the Stack operations are implemented by the standard Ruby Array class.
# initialization stack = Array.new # pushing an item onto the stack stack.push("item") stack << "item2" # popping an item off the stack top_item = stack.pop # peeking at the top item puts stack.last puts stack[-1] # checking if the stack is empty puts stack.empty? # checking the size of the stack puts stack.size puts stack.count puts stack.length