Parsing “pick up” action in a text-based RPG

Question

I’m coding a text-based RPG and I have my controls working: I have a string checking what you write in against an array of if statements.

It can get it right with everything other than my pick up action.

My if statements are set out as follows:

int game_main() { 

    string PlayerOption;

    //I have a few lines of cout statements just for my gui/hud

    cin >> PlayerOption;

    if (PlayerOption == "look") { 
        //it’s then just calling a script from a separate header file 
    }
    else if (PlayerOption == "pick up") {
        //another script from that header 
    }

My look command and all my others work but I don’t know how to set it up right.

I've tried putting it like "pick up", I tried it like "pick"" ""up" and a couple other ways but I don’t know how to properly write the expression.

Even then my problem might be with my string and not my if statement so any suggestions would be greatly appreciated.

And I think @DMGregory might be right about the word boundaries because even with that command if I make it accept "pick" it works it’s only when I ask it for two words it really breaks

Is there any way I could get around that?

Answer 1

Using cin by itself is not going to work in all cases because it automatically stops at whitespace. It will be much easier to grab the whole string at once and parse it into "commands" and "arguments":

#include <algorithm>
#include <string>
#include <utility>
#include <vector>

std::vector<std::string> Split(const std::string& string, char delim = ',', bool skip_empty = true) noexcept;
std::pair<std::string, std::vector<std::string>> ParsePlayerOption(const std::string& playeroption);
void Pick(const std::vector<std::string>& args);
void Look(const std::vector<std::string>& args);

std::vector<std::string> Split(const std::string& string, char delim /*= ','*/, bool skip_empty /*= true*/) noexcept {
    std::size_t potential_count = 1 + std::count(string.begin(), string.end(), delim);
    std::vector<std::string> result;
    result.reserve(potential_count);
    std::string curString;

    std::stringstream ss;
    ss.str(string);
    ss.seekg(0);
    ss.seekp(0);
    ss.clear();

    while(std::getline(ss, curString, delim)) {
        if(skip_empty && curString.empty()) continue;
        result.push_back(curString);
    }
    if(!skip_empty && ss.eof() && string.back() == delim) {
        result.push_back(std::string{});
    }
    result.shrink_to_fit();
    return result;
}


std::pair<std::string, std::vector<std::string>> ParsePlayerOption(const std::string& playeroption) {
    const auto first_space_pos = playeroption.find_first_of(' ');
    std::string command = playeroption.substr(0, first_space_pos);
    std::string args_list = playeroption.substr(first_space_pos);
    auto args = Split(args_list, ' ');
    return std::make_pair(command, args);
}

void Pick(const std::vector<std::string>& args) {
    if(args.front() == "up") {
        std::vector<std::string> item_list{args.begin() + 1, args.end()};
        DoPickUp(item_list);
    } else { //Not a "pick up" command. Could be like "pick flower".
        DoPick(args);
    }
}

int game_main() { 

    string PlayerOption;

    //I have a few lines of cout statements just for my gui/hud
    std::getline(std::cin, PlayerOption);

    const auto [command,args] = ParsePlayerOption(PlayerOption);

    if (command == “look”) { 
        //Do look command
        Look(args); //Trivial to implement
    } else if (command == “pick") {
        //Do partial "pick" command.
        Pick(args);
    }
}

Answer 2

Another option: use single word tokens.

Instead of using pick up for your command, use pickup.

And do the same for the parameters.

This will simplify the parsing, the processing, the documentation, etc. of the game.