86   static const StringWeight<L, S> &Zero() {  in Zero()  function
347     w = StringWeight<L, S>::Zero();
374   if (w1 == StringWeight<L, S>::Zero())  in Plus()
376   if (w2 == StringWeight<L, S>::Zero())  in Plus()
397   if (w1 == StringWeight<L, STRING_LEFT>::Zero())  in Plus()
399   if (w2 == StringWeight<L, STRING_LEFT>::Zero())  in Plus()
418   if (w1 == StringWeight<L, STRING_RIGHT>::Zero())  in Plus()
420   if (w2 == StringWeight<L, STRING_RIGHT>::Zero())  in Plus()
438   if (w1 == StringWeight<L, S>::Zero() || w2 == StringWeight<L, S>::Zero())  in Times()
439     return StringWeight<L, S>::Zero();  in Times()
465   if (w2 == StringWeight<L, S>::Zero())  in Divide()
467   else if (w1 == StringWeight<L, S>::Zero())  in Divide()
468     return StringWeight<L, S>::Zero();  in Divide()
495   if (w2 == StringWeight<L, STRING_RIGHT>::Zero())  in Divide()
497   else if (w1 == StringWeight<L, STRING_RIGHT>::Zero())  in Divide()
498     return StringWeight<L, STRING_RIGHT>::Zero();  in Divide()
525   if (w2 == StringWeight<L, STRING_RIGHT_RESTRICT>::Zero())  in Divide()
527   else if (w1 == StringWeight<L, STRING_RIGHT_RESTRICT>::Zero())  in Divide()
528     return StringWeight<L, STRING_RIGHT_RESTRICT>::Zero();  in Divide()