# File lib/amalgalite/boolean.rb, line 31
      def to_bool( val )
        return false if val.nil?
        unless defined? @to_bool
          @to_bool = {}
          true_values.each  { |t| @to_bool[t] = true  }
          false_values.each { |f| @to_bool[f] = false }
        end
        return @to_bool[val.to_s.downcase]
      end