錯誤：在'單詞'前缺少模板參數

Question

這是一個程序，它從用戶讀取15個單詞，並在將它們存儲在數組中之前通過散列算法運行它們。然後將哈希值顯示給用戶，並且用戶可以查詢數組中的特定單詞。當我嘗試運行它，我得到如下編譯錯誤：

11 error: missing template arguments before 'words' 
    11 error: expected ';' before 'words' 
    21 error: 'words' was not declared in this scope 
    27 error: 'words' was not declared in this scope 

的代碼如下：

#include <iostream> 
#include <string> 
#include <cstring> 

using namespace std; 

int main() 
{ 
    int x; 
    string input; 
    hash words; //from class hash defined below 
    bool query; 
    bool found; 

    cout<<"Please enter 15 words to be stored in a database."<<endl; 

    for(x = 1; x <= 15; x++) 
    { 
     cout<<"Word "<<x<<": "; 
     cin>>input; //new word 
     words.addHash(input); //calls addHash function in hash class 
    } 

    cout<<"Here are the hashes: "<<endl; 
    words.display(); //calls display function in hash class 

    cout<<"You can now query the database for a specific word. To stop, type 'stop'."<<endl; 
    //search words database 
    do 
    { 
     cout<<"Query: "; 
     cin>>input; 

     //more specifically, this calls search function to query words for <user_input> 
     if (input != "stop") 
     { 
      found = words.search(input); 
      if (found == true) 
      { 
       cout<<"Yes, that word was found in the database."<<endl; 
      } 
      else 
      { 
       cout<<"No, that word was NOT found in the database." <<endl; 
      }; 
     } 
     else 
     { 
      query = false; 
     }; 


    } while ((query) && (input != "stop")); 

    return 0; 
}; 

class hash { 

private: 

    int y; 
    std::string hashes[23]; 
    std::string newHash; 
    char first_letter; 
    char last_letter; 
    int location; 
    int z; 
    std::string queryHash; 
    bool found; 

public: 

    //first, the constructor for the hash algorithm 
    hash() 
    { 
     for (y = 0; y < 23; y++) 
     { 
      hashes[y] = "_"; 
     } 
    }; 


    void addHash(std::string newHash) 
    { 
     first_letter = newHash.at(0); 
     last_letter = newHash.at(newHash.size() - 1); 

     location = ((((int)first_letter) + ((int)last_letter)) % 23); 

     do 
     { 
      if (location == 23) 
      { 
       location = 0; 
      } 
      else 
      { 
       location = location + 1; 
      } 

      hashes[location] = newHash; 

     } while (hashes[location] != "_"); 

    }; 

    //prints out ALL contents of the 'database' 
    void display() 
    { 
     for (z = 0; z < 23; z++) 
     { 
      cout<<hashes[z]<<endl; 
     } 
    }; 

    //searches the 'database' for the specific word 
    bool search(std::string queryHash) 
    { 
     first_letter = queryHash.at(0); 
     last_letter = queryHash.at(queryHash.size() - 1); 

     location = ((((int)first_letter) + ((int)last_letter)) % 23); 

     do 
     { 
      if (location == 23) 
      { 
       location = 0; 
      } 
      else 
      { 
       location = location + 1; 
      } 

      hashes[location] = newHash; 

     } while ((hashes[location] != "_") && (hashes[location] != queryHash)); 

     if (hashes[location] == queryHash) 
     { 
      found = true; 
     } 
     else 
     { 
      found = false; 
     } 
     return found; 
    }; 
}; 

更新：我modifyed如下面的代碼，但仍得到相同的錯誤。

#include <iostream> 
#include <string> 
#include <cstring> 

using std::cin; 
using std::cout; 
using std::endl; 
using std::string; 

class hash; //forward declaration 

int main() 
{ 
    int x; 
    string input; 
    hash words; //from class hash defined below 
    bool query; 
    bool found; 

    cout<<"Please enter 15 words to be stored in a database."<<endl; 

    for(x = 1; x <= 15; x++) 
    { 
     cout<<"Word "<<x<<": "; 
     cin>>input; //new word 
     words.addHash(input); //calls addHash function in hash class 
    } 

    cout<<"Here are the hashes: "<<endl; 
    words.display(); //calls display function in hash class 

    cout<<"You can now query the database for a specific word. To stop, type 'stop'."<<endl; 
    //search words database 
    do 
    { 
     cout<<"Query: "; 
     cin>>input; 

     //more specifically, this calls search function to query words for <user_input> 
     if (input != "stop") 
     { 
      found = words.search(input); 
      if (found == true) 
      { 
       cout<<"Yes, that word was found in the database."<<endl; 
      } 
      else 
      { 
       cout<<"No, that word was NOT found in the database." <<endl; 
      }; 
     } 
     else 
     { 
      query = false; 
     }; 


    } while ((query) && (input != "stop")); 

    return 0; 
}; 

class hash { 

private: 

    int y; 
    std::string hashes[23]; 
    std::string newHash; 
    char first_letter; 
    char last_letter; 
    int location; 
    int z; 
    std::string queryHash; 
    bool found; 

public: 

    //first, the constructor for the hash algorithm 
    hash() 
    { 
     for (y = 0; y < 23; y++) 
     { 
      hashes[y] = "_"; 
     } 
    }; 


    void addHash(std::string newHash) 
    { 
     first_letter = newHash.at(0); 
     last_letter = newHash.at(newHash.size() - 1); 

     location = ((((int)first_letter) + ((int)last_letter)) % 23); 

     do 
     { 
      if (location == 23) 
      { 
       location = 0; 
      } 
      else 
      { 
       location = location + 1; 
      } 

      hashes[location] = newHash; 

     } while (hashes[location] != "_"); 

    }; 

    //prints out ALL contents of the 'database' 
    void display() 
    { 
     for (z = 0; z < 23; z++) 
     { 
      cout<<hashes[z]<<endl; 
     } 
    }; 

    //searches the 'database' for the specific word 
    bool search(std::string queryHash) 
    { 
     first_letter = queryHash.at(0); 
     last_letter = queryHash.at(queryHash.size() - 1); 

     location = ((((int)first_letter) + ((int)last_letter)) % 23); 

     do 
     { 
      if (location == 23) 
      { 
       location = 0; 
      } 
      else 
      { 
       location = location + 1; 
      } 

      hashes[location] = newHash; 

     } while ((hashes[location] != "_") && (hashes[location] != queryHash)); 

     if (hashes[location] == queryHash) 
     { 
      found = true; 
     } 
     else 
     { 
      found = false; 
     } 
     return found; 
    }; 
}; 

Answer 1

名稱hash與std::hash衝突。使用using namespace std;

添加std::每個標識符從命名空間std或添加像using std::cin;每個標識符，而不是using namespace std;

UPDATE聲明

爲了解決這個問題，

1. 停止：你代碼應該是這樣的：

   #include <iostream> 
   #include <string> 
   #include <cstring> 
   
   using std::cin; 
   using std::cout; 
   using std::endl; 
   using std::string; 
   
   // delcaration of a class 
   class hash { 
   
   private: 
   
       int y; 
       std::string hashes[23]; 
       std::string newHash; 
       char first_letter; 
       char last_letter; 
       int location; 
       int z; 
       std::string queryHash; 
       bool found; 
   
   public: 
       hash(); 
       void addHash(std::string newHash); 
       void display(); 
       bool search(std::string queryHash); 
   }; 
   
   int main() 
   { 
       int x; 
       string input; 
       hash words; //from class hash defined below 
       bool query; 
       bool found; 
   
       cout<<"Please enter 15 words to be stored in a database."<<endl; 
   
       for(x = 1; x <= 15; x++) 
       { 
        cout<<"Word "<<x<<": "; 
        cin>>input; //new word 
        words.addHash(input); //calls addHash function in hash class 
       } 
   
       cout<<"Here are the hashes: "<<endl; 
       words.display(); //calls display function in hash class 
   
       cout<<"You can now query the database for a specific word. To stop, type 'stop'."<<endl; 
       //search words database 
       do 
       { 
        cout<<"Query: "; 
        cin>>input; 
   
        //more specifically, this calls search function to query words for <user_input> 
        if (input != "stop") 
        { 
         found = words.search(input); 
         if (found == true) 
         { 
          cout<<"Yes, that word was found in the database."<<endl; 
         } 
         else 
         { 
          cout<<"No, that word was NOT found in the database." <<endl; 
         } 
        } 
        else 
        { 
         query = false; 
        } 
   
   
       } while ((query) && (input != "stop")); 
   
       return 0; 
   } 
   
   // below are definitions of member functions 
   
   //first, the constructor for the hash algorithm 
   hash::hash() 
   { 
       for (y = 0; y < 23; y++) 
       { 
        hashes[y] = "_"; 
       } 
   } 
   
   void hash::addHash(std::string newHash) 
   { 
       first_letter = newHash.at(0); 
       last_letter = newHash.at(newHash.size() - 1); 
   
       location = ((((int)first_letter) + ((int)last_letter)) % 23); 
   
       do 
       { 
        if (location == 23) 
        { 
         location = 0; 
        } 
        else 
        { 
         location = location + 1; 
        } 
   
        hashes[location] = newHash; 
   
       } while (hashes[location] != "_"); 
   
   } 
   
   //prints out ALL contents of the 'database' 
   void hash::display() 
   { 
       for (z = 0; z < 23; z++) 
       { 
        cout<<hashes[z]<<endl; 
       } 
   } 
   
   //searches the 'database' for the specific word 
   bool hash::search(std::string queryHash) 
   { 
       first_letter = queryHash.at(0); 
       last_letter = queryHash.at(queryHash.size() - 1); 
   
       location = ((((int)first_letter) + ((int)last_letter)) % 23); 
   
       do 
       { 
        if (location == 23) 
        { 
         location = 0; 
        } 
        else 
        { 
         location = location + 1; 
        } 
   
        hashes[location] = newHash; 
   
       } while ((hashes[location] != "_") && (hashes[location] != queryHash)); 
   
       if (hashes[location] == queryHash) 
       { 
        found = true; 
       } 
       else 
       { 
        found = false; 
       } 
       return found; 
   }