command line options parser

//(incomplete!) command line options utility
#pragma once
#include <string>
#include <algorithm>
#include <vector>

class ProgramOptions{
private:
    const std::string EMPTY{""};
    std::vector<std::string> _tokens;
public:
    ProgramOptions(const int argc, char* argv[]){
        _tokens.reserve(argc);
        for(int i = 0; i < argc; ++i){
            _tokens.emplace_back(argv[i]);
        }
    }
    const std::string& getOption(const size_t index) const{
        if(index >= _tokens.size()){
            return EMPTY;
        }
        return _tokens[index];
    }
    const std::string& getOption(const std::string& option) const{
        auto itr = std::find(_tokens.begin(), _tokens.end(), option);
        if(itr != _tokens.end() && ++itr != _tokens.end()){
            return *itr;
        }
        return EMPTY;
    }
    std::string toString() const{
        std::string out;
        static const std::string newLine{"\n"};
        for(const auto& str : _tokens){
            out += str+newLine;
        }
        return out;
    }
    bool optionExists(const std::string& option) const {
        return std::find(_tokens.begin(), _tokens.end(), option) != _tokens.end();
    }
};