32     test(std::string("\\(a\\)"), std::regex_constants::basic, 1);  in main()
33     test(std::string("\\(a[bc]\\)"), std::regex_constants::basic, 1);  in main()
34     test(std::string("\\(a\\([bc]\\)\\)"), std::regex_constants::basic, 2);  in main()
35     test(std::string("(a([bc]))"), std::regex_constants::basic, 0);  in main()
37     test(std::string("\\(a\\)"), std::regex_constants::extended, 0);  in main()
38     test(std::string("\\(a[bc]\\)"), std::regex_constants::extended, 0);  in main()
39     test(std::string("\\(a\\([bc]\\)\\)"), std::regex_constants::extended, 0);  in main()
40     test(std::string("(a([bc]))"), std::regex_constants::extended, 2);  in main()
42     test(std::string("\\(a\\)"), std::regex_constants::ECMAScript, 0);  in main()
43     test(std::string("\\(a[bc]\\)"), std::regex_constants::ECMAScript, 0);  in main()
44     test(std::string("\\(a\\([bc]\\)\\)"), std::regex_constants::ECMAScript, 0);  in main()
45     test(std::string("(a([bc]))"), std::regex_constants::ECMAScript, 2);  in main()
47     test(std::string("\\(a\\)"), std::regex_constants::awk, 0);  in main()
48     test(std::string("\\(a[bc]\\)"), std::regex_constants::awk, 0);  in main()
49     test(std::string("\\(a\\([bc]\\)\\)"), std::regex_constants::awk, 0);  in main()
50     test(std::string("(a([bc]))"), std::regex_constants::awk, 2);  in main()
52     test(std::string("\\(a\\)"), std::regex_constants::grep, 1);  in main()
53     test(std::string("\\(a[bc]\\)"), std::regex_constants::grep, 1);  in main()
54     test(std::string("\\(a\\([bc]\\)\\)"), std::regex_constants::grep, 2);  in main()
55     test(std::string("(a([bc]))"), std::regex_constants::grep, 0);  in main()
57     test(std::string("\\(a\\)"), std::regex_constants::egrep, 0);  in main()
58     test(std::string("\\(a[bc]\\)"), std::regex_constants::egrep, 0);  in main()
59     test(std::string("\\(a\\([bc]\\)\\)"), std::regex_constants::egrep, 0);  in main()
60     test(std::string("(a([bc]))"), std::regex_constants::egrep, 2);  in main()