17.3. Regular Expressions

A regular expression is a way of describing a sequence of characters. Regular expressions are a stunningly powerful computational device. However, describing the languages used to define regular expressions is well beyond the scope of this Primer. Instead, we’ll focus on how to use the C++ regular-expression library (RE library), which is part of the new library. The RE library, which is defined in the regex header, involves several components, listed in Table 17.4.

Table 17.4. Regular Expression Library Components

The regex class represents a regular expression. Aside from initialization and assignment, regex has few operations. The operations on regex are listed in Table 17.6 (p. 731).

The functions regex_match and regex_search determine whether a given character sequence matches a given regex. The regex_match function returns true if the entire input sequence matches the expression; regex_search returns true if there is a substring in the input sequence that matches. There is also a regex_replace function that we’ll describe in § 17.3.4 (p. 741).

The arguments to the regex functions are described in Table 17.5 (overleaf). These functions return a bool and are overloaded: One version takes an additional argument of type smatch . If present, these functions store additional information about a successful match in the given smatch object.

Table 17.5. Arguments to regex_search and regex_match