class RubyParserStuff::StackState

def initialize name, debug=false
  @name = name
  @stack = [false]
  @debug = debug
end

def inspect
  "StackState(#{@name}, #{@stack.inspect})"
end

def is_in_state
  log :is_in_state if debug
  @stack.last
end

def lexpop
  raise if @stack.size == 0
  a = @stack.pop
  b = @stack.pop
  @stack.push(a || b)
  log :lexpop if debug
end

def log action
  c = caller[1]
  c = caller[2] if c =~ /expr_result/
  warn "%s_stack.%s: %p at %s" % [name, action, @stack, c.clean_caller]
  nil
end

def pop
  r = @stack.pop
  @stack.push false if @stack.empty?
  log :pop if debug
  r
end

def push val
  @stack.push val
  log :push if debug
end

def reset
  @stack = [false]
  log :reset if debug
end

def restore oldstate
  @stack.replace oldstate
  log :restore if debug
end

def store base = false
  result = @stack.dup
  @stack.replace [base]
  log :store if debug
  result
end