def inspect
      expr = @expr || @unit.expr
      expr = (expr) ? ","+expr.inspect : ""
      sufx = (@@verbose_inspect) ? " "+@unit.inspect : ""
      self.class.to_s+"["+Unit::Utils.num_inspect(@value)+expr+"]"+sufx
    end
def inspect
      expr = @expr || @unit.expr
      expr = (expr) ? ","+expr.inspect : ""
      sufx = (@@verbose_inspect) ? " "+@unit.inspect : ""
      self.class.to_s+"["+Unit::Utils.num_inspect(@value)+expr+"]"+sufx
    end
Inspect String.
 @return [String]