// and N2.
//
// e ( NI ) o -> e ( NI ) o

// getStrongTypeN0 maps character's directional code to strong type as required
// by rule N0.
//
// TODO: have separate type for "strong" directionality.
func (p *bracketPairer) getStrongTypeN0(index int) Class {
	switch p.codesIsolatedRun[index] {
	// in the scope of N0, number types are treated as R