错误：''''之前的'＆'令牌

Question

我在下面的标题中遇到了构造函数签名的问题。编译器给我的消息：

error: expected ')' before '&' token 

但我不知道为什么会发生这种错误，我不认为原因是编译器指示。

#ifndef TextQuery 
#define TextQuery 

#include <fstream> 
#include <map> 
#include <memory> 
#include <set> 
#include <string> 
#include <sstream> 
#include <vector> 

using std::ifstream; 
using std::map; 
using std::shared_ptr; 
using std::set; 
using std::string; 
using std::istringstream; 
using std::vector; 

class TextQuery 
{ 
    public: 
     using line_no = vector<string>::size_type; 
     TextQuery(ifstream &); //!!!!error: expected ')' before '&' token 
    private: 
     shared_ptr<vector<string>> file; //input file 
     //map of each word to the set of the lines in which that word appears 
     map<string, shared_ptr<set<line_no>>> wm; 
}; 

//read the input file and build the map of lines to line numbers 
TextQuery::TextQuery(ifstream &is) : file(new vector<string>) 
{ 
    string text; 
    while(getline(is, text)) { //for each line in the file 
     file->push_back(text); //remember this line of text 
     int n = file->size() - 1; //the current line number 
     istringstream line(text); //separate the line into words 
     string word; 
     while(line >> word) { //for each word in that line 
      //if word isn't already in wm, subscripting adds a new entry 
      auto &lines = wm[word]; //lines id a shared_ptr 
      if(!lines) //that pointer is null the first time we see word 
       lines.reset(new set<line_no>); //allocate a new set 
      lines->insert(n); //insert this line number 
     } 
    } 
} 

#endif 

Answer 1

提示：这里有什么问题？

#ifndef TextQuery 
#define TextQuery 

// .. 

class TextQuery { 
    // ... 
}; 

#endif