(	)	*	+	?	\	a	d	|	other	ε
→ S	( alt0 ) mod seq alt					\ esc mod seq alt	a char mod seq alt	d char mod seq alt		other char mod seq alt	ε
alt0	( alt0 ) mod seq alt					\ esc mod seq alt	a char mod seq alt	d char mod seq alt		other char mod seq alt
alt		ε							| seq0 alt alt		ε
esc							a alpha	d digit
mod	ε	ε	* star	+ plus	? opt	ε	ε	ε	ε	ε	ε
seq0	( alt0 ) mod seq					\ esc mod seq	a char mod seq	d char mod seq		other char mod seq
seq	( alt0 ) mod seq seq	ε				\ esc mod seq seq	a char mod seq seq	d char mod seq seq	ε	other char mod seq seq	ε
terminal	pop	pop	pop	pop	pop	pop	pop	pop	pop	pop
Z0											accept