C++ Basic regex_match and regex_search Examples


Example

const auto input = "Some people, when confronted with a problem, think \"I know, I'll use regular expressions.\""s;
smatch sm;

cout << input << endl;

// If input ends in a quotation that contains a word that begins with "reg" and another word begining with "ex" then capture the preceeding portion of input
if (regex_match(input, sm, regex("(.*)\".*\\breg.*\\bex.*\"\\s*$"))) {
    const auto capture = sm[1].str();
    
    cout << '\t' << capture << endl; // Outputs: "\tSome people, when confronted with a problem, think\n"
    
    // Search our capture for "a problem" or "# problems"
    if(regex_search(capture, sm, regex("(a|d+)\\s+problems?"))) {
        const auto count = sm[1] == "a"s ? 1 : stoi(sm[1]);
        
        cout << '\t' << count << (count > 1 ? " problems\n" : " problem\n"); // Outputs: "\t1 problem\n"
        cout << "Now they have " << count + 1 << " problems.\n"; // Ouputs: "Now they have 2 problems\n"
    }
}

Live Example