Quantifiers
The asterisk (*) and plus (+) are formally called quantifiers. Figure 14.22 lists all the quantifiers. We’ve already discussed how the asterisk (*) and plus (+) quantifiers work. All quantifiers affect only the subexpression immediately preceding the quantifier. Quantifier question mark (?) matches zero or one occurrences of the expression that it quantifies. A set of braces containing one number ({n}) matches exactly n occurrences of the expression it quantifies. We demonstrate this quantifier to validate the zip code in Fig. 14.20 at line 40. Including a comma after the number enclosed in braces matches at least n occurrences of the quantified expression. The set of braces containing two numbers ({n,m}), matches between n and ...
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