Wie konvertiert man in C++ eine Zeichenfolge Zeile für Zeile?

Question

habe ich versucht, diesen Code auf Eclipse mit MinGW und der Online-C++ Editor: https://www.tutorialspoint.com/compile_cpp_online.php

Ich weiß nicht, warum stoi nicht funktioniert? Ich versuche, eine Zeichenfolge Zeile für Zeile aus einem Textdokument in eine Ganzzahl zu konvertieren. Würde es ein Bibliotheks-Problem sein oder unterstützt MinGW es nicht? Ich habe es auch mit std :: und ohne es versucht (ich glaube wirklich nicht, dass ich es brauchte, da die std ein Namespace ist).

Die Fehler:

08:54:40 **** Incremental Build of configuration Debug for project test **** 
Info: Internal Builder is used for build 
g++ -O0 -g3 -Wall -c -fmessage-length=0 -o test.o "..\\test.cpp" 
..\test.cpp: In function 'int main()': 
..\test.cpp:30:51: error: 'stoi' was not declared in this scope 
        questionsAmt = stoi(array[0]); 
               ^
..\test.cpp:67:48: error: 'stoi' is not a member of 'std' 
        quizpoints[QUESTIONNUM] = std::stoi(array[loop]); 
               ^
..\test.cpp:87:41: error: 'stoi' is not a member of 'std' 
        AnswerArrayCount = std::stoi(array[loop]); 
             ^

08:54:41 Build Finished (took 903ms) 

Der Code:

#include <iostream> 
#include <fstream> 
#include <string> 
using namespace std; 
int main() 
{ 
    int MAXSIZE = 1024; 
    string array[MAXSIZE]; // creates array to hold names 
    string line; //this will contain the data read from the file 
    int questionsAmt; 
    int loop=0; //short for loop for input 
    int QUESTIONNUM = 0; //Question number to keep track in array. 
    int isMC = 0; //Question number to keep track in array. 
    int AnswerArrayCount = 0; //Question number to keep track in array. 
    string AnswerArray[MAXSIZE]; //Question number to keep track in array. 

    int isTF = 0; //Question number to keep track in array. 
    int quizpoints[MAXSIZE]; //this will contain the data read from the file 
    string quizquestions[MAXSIZE]; //this will contain the data read from the file 
    string quizanswer[MAXSIZE]; //this will contain the data read from the file 

    ifstream myfile ("testquestions.txt"); //opening the file. 
    if (myfile.is_open()) //if the file is open 
    { 
     while (! myfile.eof()) //while the end of file is NOT reached 
     { 
      getline (myfile,line); //get one line from the file 
      array[loop] = line;//convert get whole line into an array string 
       questionsAmt = stoi(array[0]); 

      for (int i = 0; i < questionsAmt; i++) 
      if(line=="TF"){ 
       QUESTIONNUM++; //question 1,2,3, 
       isTF = 1;//setup next loop getline 
       loop++; 
      } 
      if(isTF == 1){ 
       //points 
       quizpoints[QUESTIONNUM] = stoi(array[loop]); 
       isTF = 2;//setup next loop getline 
       loop++; 
      } 
      if(isTF == 2){ 
       //TF question 
       quizquestions[QUESTIONNUM] = array[loop]; 
       QUESTIONNUM++; //question 1,2,3, 
       isTF = 3;//setup next loop getline 

       loop++; 
      } 
      if(isTF == 3){ 
       //TF answer 
        quizanswer[QUESTIONNUM] = array[loop]; 
        QUESTIONNUM++; //question 1,2,3, 
       loop++; 
      } 


      if(line=="MC"){ 
       QUESTIONNUM++; //question 1,2,3, 
       isMC = 1;//setup next loop getline 
       loop++; 
      } 
      if(isMC == 1){ 
       //points 
       quizpoints[QUESTIONNUM] = std::stoi(array[loop]); 

       cout<<quizquestions[QUESTIONNUM]<<endl; 

       isMC = 2;//setup next loop getline 
       loop++; 
      } 
      if(isMC == 2){ 
       //MC question 
       quizquestions[QUESTIONNUM] = array[loop]; 

       cout<<quizquestions[QUESTIONNUM]<<endl; 

       QUESTIONNUM++; //question 1,2,3, 
       isMC = 3;//setup next loop getline 

       loop++; 
      } 
      if(isMC == 3){ 
       //MC answer string array 
       AnswerArrayCount = std::stoi(array[loop]); 
       //convert to int 
       string AnswerArray[AnswerArrayCount] = array[loop]; 
       //Question number to keep track in array. 

       cout<<AnswerArray[AnswerArrayCount]<<endl; 

       AnswerArrayCount = AnswerArrayCount - 1 ; 
       //Question number to keep track in array. 
       loop++; 
      } 
      if(AnswerArrayCount >= 1){ 
       //MC answer string array 
       AnswerArray[AnswerArrayCount] = array[loop]; 
       //Question number to keep track in array. 

       cout<<AnswerArray[AnswerArrayCount]<<endl; 

       AnswerArrayCount = AnswerArrayCount - 1 ; 
       //Question number to keep track in array. 
       loop++; 
      } 


      // loop++; 
     } 
     //cout << array[0] << endl; //and output it 
     //int questionsAmt = array[0]; //and output it 

     myfile.close(); //closing the file 
    } 
    else 
     { 
     cout << "Unable to open file"; //if the file is not open output 

    // system("PAUSE"); 
     } 
    return 0; 

} 

Die Datei:

13 
TF 
5 
There exist birds that cannot fly? 
true 
MC 
10 
Who was the President of the USA in 1991? 
6 
Richard Nixon 
Gerald Ford 
Jimmy Carter 
Ronald Reagan 
George Bush Sr. 
Bill Clinton 
E 
TF 
10 
The city of Boston hosted the 2004 Summer Olympics? 
false 

Answer 1

Go auf Projektoptionen -> Compilation Option und setzen diese g++ -std=c++11 -o main *.cpp als Kompilation Befehl.

-std=c++11 ermöglichen C++ 11 Feature

Sie müssen dies tun, weil stoi ein C++ 11 functionnality.

Auf dieser Seite der Dokumentation: http://www.cplusplus.com/reference/string/stoi/

Sie können eine litle Warnung picto (Terekay Zeichen) im oberen Teil der Seite sehen. Das besagt, dass Sie nur auf C++ 11