class Haml::Parser

def filter(name)
  raise Error.new(Error.message(:invalid_filter_name, name)) unless name =~ /^\w+$/
  @filter_buffer = String.new
  if filter_opened?
    @flat = true
    # If we don't know the indentation by now, it'll be set in Line#tabs
    @flat_spaces = @indentation * (@template_tabs+1) if @indentation
  end
  ParseNode.new(:filter, @index, :name => name, :text => @filter_buffer)
end