There is no single quantifier that means “exactly m or n times”. The way you are doing it is fine.
An alternative is:
X{m}(X{k})?
where m < n and k is the value of n-m.
There is no single quantifier that means “exactly m or n times”. The way you are doing it is fine.
An alternative is:
X{m}(X{k})?
where m < n and k is the value of n-m.