std_lib_facilities.h編譯練習時出現C++錯誤

Question

我正在嘗試編寫練習中的程序Bjarne Stroustrup編程原理與實踐使用C++該程序應該是一個名爲Bulls and Cows的小遊戲，用戶嘗試猜測四位數字。這是我的代碼至今：

#include "../Library/std_lib_facilities.h" 

class string_error{}; 

/* 
* Method to determine if an integer is 
* in a vector 
*/ 
bool contains(vector<int> v,int k){ 

} 

int string_to_int(string s){ 
    if(s == "0") return 0; 
    else if(s == "1")return 1; 
    else if(s == "2")return 2; 
    else if(s == "3")return 3; 
    else if(s == "4")return 4; 
    else if(s == "5")return 5; 
    else if(s == "6")return 6; 
    else if(s == "7")return 7; 
    else if(s == "8")return 8; 
    else if(s == "9")return 9; 
    else throw string_error(); 
} 

int main(){ 

    /* 
    * There is an int vector with the numbers 
    * of the answer in it 
    * 
    * There is also an int vector with the numbers 
    * of the user's guess 
    * 
    * User inputs a four digit integer that is read as 
    * a string called str_guess 
    * 
    * for each digit in the guess string the digit is 
    * converted to an integer and added to the guess vector 
    * 
    * The guess vector is then run through for each digit in the vector 
    * each digit is checked against the answer at the same index 
    * if the digit in the answer at that index number is not the same as the 
    * digit in the guess vector then the digit is checked if the answer 
    * vector contains it at all 
    * 
    * for each number that is correct for both the value and position 
    * 1 is added to the bull value 
    * for each number that is within the answer value but not in the correct position 
    * 1 is added to the cow value 
    * 
    * The bull and cow values are displayed after the user enters their guess 
    * 
    * The user is prompted for a guess until their guess returns 4 bulls 
    */ 

    vector<int> answer; 
    answer.push_back(7); 
    answer.push_back(9); 
    answer.push_back(2); 
    answer.push_back(4); 

    string str_guess = ""; 
    cout << "Enter a four digit integer as a guess"; 
    cin >> str_guess; 
    vector<int> guess; 
    for(int i = 0; i < 4; i++){ 
     int guess_digit = string_to_int(str_guess[i]); 
     guess.push_back(guess_digit); 
    } 
    cout << "Length of guess vector: " + guess.size(); 



} 

正如你可以看到我使用Mr.Stroustrup的頭文件std_lib_facilities.h（here）不幸的是，每當我嘗試編譯我的程序我得到這個錯誤：

In file included from ../Bulls_and_Cows.cpp:13: 
../../Library/std_lib_facilities.h:106:38: error: no matching constructor for initialization of 'std::string' (aka 'basic_string<char, char_traits<char>, allocator<char> >') 
     template<class S> String(S s) :std::string(s) {} 

我在使用eclipse和mac os gcc編譯器的mac上。任何幫助你可以提供我將不勝感激。謝謝

Answer 1

你的功能string_to_int接收一個字符串，並傳遞一個char

int guess_digit = string_to_int(str_guess[i]); 
//          ^^^ access a position of the string that is a char