使用未聲明的標識符'top';你的意思是'流行'嗎？

Question

好的，第一次使用stackoverflow，請和我一起裸照。

我的教授給了我一些關於boggle遊戲回溯的C++代碼。但它不會爲我編譯。我得到這個錯誤，使用未聲明的標識符'頂部';你的意思是'流行'嗎？並且如果需要的話，則代碼的其餘部分。謝謝！

// Maze01.cpp : Defines the entry point for the console application. 

#include <cstdlib> 
#include <iostream> 
#include <stack> 
using namespace std; 
template<class T> 
class Stack : public stack<T> { 
public: 
    T pop() { 
     T tmp = top(); //<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< 
     stack<T>::pop(); 
     return tmp; 
    } 
}; 

class Cell { 
public: 
    Cell(int i = 0, int j = 0) { 
     x = i; y = j; 
    } 
    bool operator== (const Cell& c) const { 
     return x == c.x && y == c.y; 
    } 
private: 
    int x, y; 
    friend class Maze; 
}; 

class Maze { 
public: 
    Maze(); 
    void exitMaze(); 
private: 
    Cell currentCell, exitCell, entryCell; 
    const char exitMarker, entryMarker, visited, passage, wall; 
    Stack<Cell> mazeStack; 
    char **store;   // array of strings; 
    void pushUnvisited(int, int); 
    int rows, cols; 
    friend ostream& operator<< (ostream& out, const Maze& maze) { 
     for (int row = 0; row <= maze.rows + 1; row++) 
      out << maze.store[row] << endl; 
     out << endl; 
     return out; 
    } 
}; 

Maze::Maze() : exitMarker('e'), entryMarker('m'), visited('.'), 
passage('0'), wall('1') { 
    Stack<char*> mazeRows; 
    char str[80], *s; 
    int col, row = 0; 
    cout << "Enter a rectangular maze using the following " 
     << "characters:\nm - entry\ne - exit\n1 - wall\n0 - passage\n" 
     << "Enter one line at at time; end with Ctrl-z:\n"; 
    while (cin >> str) 
    { 
     row++; 
     cols = strlen(str); 
     s = new char[cols + 3]; // two more cells for borderline columns; 
     mazeRows.push(s); 
     strcpy(s + 1, str); 
     s[0] = s[cols + 1] = wall; // fill the borderline cells with 1s; 
     s[cols + 2] = '\0'; 
     if (strchr(s, exitMarker) != 0) 
     { 
      exitCell.x = row; 
      exitCell.y = strchr(s, exitMarker) - s; 
     } 
     if (strchr(s, entryMarker) != 0) 
     { 
      entryCell.x = row; 
      entryCell.y = strchr(s, entryMarker) - s; 
     } 
    } 
    rows = row; 
    store = new char*[rows + 2];  // create a 1D array of pointers; 
    store[0] = new char[cols + 3];  // a borderline row; 
    for (; !mazeRows.empty(); row--) { 
     store[row] = mazeRows.pop(); 
    } 
    store[rows + 1] = new char[cols + 3]; // another borderline row; 
    store[0][cols + 2] = store[rows + 1][cols + 2] = '\0'; 
    for (col = 0; col <= cols + 1; col++) { 
     store[0][col] = wall;   // fill the borderline rows with 1s; 
     store[rows + 1][col] = wall; 
    } 
} 

void Maze::pushUnvisited(int row, int col) { 
    if (store[row][col] == passage || store[row][col] == exitMarker) { 
     mazeStack.push(Cell(row, col)); 
    } 
} 
void Maze::exitMaze() { 
    int row, col; 
    currentCell = entryCell; 
    while (!(currentCell == exitCell)) { 
     row = currentCell.x; 
     col = currentCell.y; 
     cout << *this;   // print a snapshot; 
     if (!(currentCell == entryCell)) 
      store[row][col] = visited; 
     pushUnvisited(row - 1, col); 
     pushUnvisited(row + 1, col); 
     pushUnvisited(row, col - 1); 
     pushUnvisited(row, col + 1); 
     if (mazeStack.empty()) { 
      cout << *this; 
      cout << "Failure\n"; 
      return; 
     } 
     else currentCell = mazeStack.pop(); 
    } 
    cout << *this; 
    cout << "Success\n"; 
} 


int main(int argc, char* argv[]) 
{ 

    Maze().exitMaze(); 
    return 0; 
} 

Answer 1

修復這樣說：

T tmp = this->top(); //<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< 

gcc5.3解釋了原因：

/tmp/gcc-explorer-compiler116315-75-7jbdnd/example.cpp: 
    In member function 'T Stack<T>::pop()': 
13 : error: there are no arguments to 'top' that depend on a template parameter, 
    so a declaration of 'top' must be available [-fpermissive] 
T tmp = top(); //<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< 
^ 
13 : note: (if you use '-fpermissive', G++ will accept your code, 
    but allowing the use of an undeclared name is deprecated) 
Compilation failed