How Can I Efficiently Extract Multiple Matching Words from a String Using std::regex?

Matching Multiple Results with std::regex: An Effective Solution

Encountering difficulties in extracting multiple matched words from a string using std::regex? A common misconception is to employ the pattern "(bS*b){0,}" to match words in a single operation. However, this approach falls short due to the optional quantifier {0,} within the pattern.

Addressing the Challenge

To address this issue and successfully match multiple results using std::regex, it's crucial to refrain from using optional quantifiers. Instead, consider the following code:

regex exp("(\b\S*\b)");
smatch res;
string str = "first second third forth";

string::const_iterator searchStart( str.cbegin() );
while ( regex_search( searchStart, str.cend(), res, exp ) )
{
    cout << ( searchStart == str.cbegin() ? "" : " " ) << res[0];  
    searchStart = res.suffix().first;
}
cout << endl;

Understanding the Solution

This updated approach involves iterating over the input string while performing regex_search repeatedly. It initializes the search start position within the string and continues matching patterns until no further matches are found. Each successful match updates the search start position to the position immediately after the matched word.

Benefits of This Approach

This optimized solution eliminates the need for using capturing groups. It's more efficient and ensures that all words in the input string are extracted and separated with spaces in the output.

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