class Treetop::Compiler::Predicate

def assign_failure
  reset_index
  super(start_index_var)
end

def assign_success
  reset_index
  assign_result epsilon_node
end

def compile(address, builder, parent_expression)
  super
  begin_comment(parent_expression)
  use_vars :result, :start_index
  obtain_new_subexpression_address
  parent_expression.prefixed_expression.compile(subexpression_address, builder)
  builder.if__(subexpression_success?) { when_success }
  builder.else_ { when_failure }
  end_comment(parent_expression)
end