symbol_stack.rb

class StackEmptyError < StandardError
end
class StackOverflowError < StandardError
end

class SymbolStack
  def initialize
    @stack = []
  end

  def push(obj)
    raise ArgumentError unless obj.instance_of? Symbol
    raise StackOverflowError if @stack.size >= 10

    @stack.push(obj)
  end

  def pop
    raise StackEmptyError if @stack.empty?
    @stack.pop
  end

  def size
    @stack.size
  end
end