Can a single quantifier match exactly n or m times in regular expressions?

Regex: Matching Exactly n or m Times

Consider the following regular expression:

X{n}|X{m}

where X represents any regular expression. This pattern aims to match a sequence where X occurs exactly n or m times.

Question:

Can we simplify this expression using a single quantifier that tests for the occurrence of X exactly n or m times?

Answer:

There is no single quantifier in regular expressions that directly specifies "exactly n or m times." The method you are using in the given expression (X{n}|X{m}) is an effective way to achieve this functionality.

Alternative Approach:

An alternative pattern you could consider is:

X{m}(X{k})?

where m < n and k equals n - m. This pattern ensures that X occurs at least m times (enforced by X{m}) and optionally occurs exactly k more times (represented by the optional group (X{k})?).

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