C++ parsing complicated file where each line specifies a command -

so need ideas on how nicely parse text file in c++. files parsing have following format :

  command_a  list of arguments   command_b  list of arguments   etc etc 

right using ifstream open file , have super long series of if-else statements determine each type of command. proving bit unwieldy (especially since of commands parsing other files...so have nested if-elses multiple ifstreams different files).

i looking way of doing not sure best approach. thinking using std::map keys command strings , values function pointers not familiar storing function pointers in map (especially if different functions of different return types, etc).

below doing. loop through file , use "getline" current line. use stringstream parse command. use long list of if-elses determine function call. each line in file comes list of arguments use stringstream parse , pass parameters function call.

the problem here two-fold

1) have very large number of if-elses (around 50)

2) of commands require me parse new files , have open ifstream within current ifstream. (see command_c)

so i'm looking easier/more efficient/prettier looking way this.

/*open file , verify validity*/ std::ifstream parsefile(filename.c_str()); if(!parsefile.good()) {     cerr<<"error: file either corrupt or not exist."<<endl;     exit(1); //terminate program }  //loop on file line line std::string line; while(!parsefile.eof()) {     std::getline(parsefile, line);     std::stringstream ss;     std::string command;     ss.str(line);     ss >> command;      if(command == "command_a")     {          float x,y,z;          ss >> x >> y >> z;           functiona(x,y,z);     }     else if(command == "command_b")     {         float a,b,c,d,e,f;         ss >> >> b >> c >> d >> e >> f;          functionb(a,b,c,d,e,f);     }      else if(command == "command_c")     {         string nextfile;         ss >> nextfile;          parsefile(nextfile); //this not recursive...this function     }     else if(...)     {       ...     }     //  etc, etc (this continues on long time)   } parsefile.close(); 

you have command map , register bunch of functions:

#include<fstream> #include<functional> #include<iostream> #include<map> #include<sstream>  int main() {      typedef std::function<bool (std::istringstream&)> command_function;     typedef std::map<std::string, command_function> command_map;      command_map map;      // register commands     map.insert(command_map::value_type("print", [](std::istringstream& s) {         std::string line;         if( ! getline(s, line)) return false;         std::cout << line << '\n';         return true;     }));      map.insert(command_map::value_type("add", [](std::istringstream& s) {         double a;         double b;         if( ! (s >> >> b)) return false;         std::cout << "a + b = " << + b  << '\n';         return true;     }));      // sample data     std::istringstream file(         "print hello world\n"         "add 1 2\n");      // command parsing     std::string line;     while(getline(file, line)) {         std::istringstream line_stream(line);         std::string command;         if(line_stream >> command >> std::ws) {             auto pos = map.find(command);             if(pos != map.end())                 pos->second(line_stream);         }     }     return 0; }