code: func (f *fieldVal) AddInt(ui uint) *fieldVal {
  	// Since the field representation intentionally provides overflow bits,
  	// it's ok to use carryless addition as the carry bit is safely part of
  	// the word and will be normalized out.
  	f.n[0] += uint32(ui)
  
  	return f
  }
docs: // AddInt adds the passed integer to the existing field value and stores the
  // result in f.  This is a convenience function since it is fairly common to
  // perform some arithemetic with small native integers.
  //
  // The field value is returned to support chaining.  This enables syntax like:
  // f.AddInt(1).Add(f2) so that f = f + 1 + f2.