C++ Basic string tokenizer

std::vector<std::string> get_tokens(std::string str, char start_delim = '<', char end_delim = '>')
{
    unsigned int first = 0, last = 0;
    std::vector<std::string> tokens {};

    while (first != std::string::npos) {
        first = str.find(start_delim);
        last = str.find(end_delim);
        tokens.push_back(str.substr(first+1,last-first-1));
        str = str.substr(last, std::string::npos);
    }

    return tokens;
}