错误:‘&’ 之前的声明符无效代币
我试图编写一个 TextQuery 程序,允许用户:
1. 输入单词
2. 读取文件
3. 打印出单词出现在哪些行以及单词在该行出现的次数。
我创建了一个名为 "TextQuery" 的类,其中包含 3 个成员函数:
1. "read_file" 读取文件并返回对向量的引用
2.“find_word”取需要搜索的单词
然后返回对地图的引用int,pair>
(第一个“int”是行号,第二个“int”是单词在该行出现的次数,“字符串”< /strong> 是整行)
3.“write_out”写入结果。
但是,当我编译程序时,我得到了这样的消息:
/home/phongcao/C++/textquery_class_1.cc:21: error: invalid declarator before ‘&’ token
我只是想知道声明符怎么会错?这是类定义部分:
#include <iostream>
#include <fstream>
#include <algorithm>
#include <map>
#include <vector>
#include <string>
using namespace std;
class TextQuery {
public:
vector<string> &read_file(ifstream &infile) const;
map< int, pair<string, int> > &find_word(const string &word) const;
void write_out(const string &word) const;
private:
vector<string> svec;
map< int, pair<string, int> > result;
}
//The following line is line 21, where I got the error!!
vector<string> &TextQuery::read_file(ifstream &infile) const {
while (getline(infile, line)) {
svec.push_back(line);
}
return svec;
}
map< int, pair<string, int> > &TextQuery::find_word(const string &word) const {
for (vector<string>::size_type i = 0; i != svec.end()-1; ++i) {
int rep_per_line = 0;
pos = svec[i].find(word, 0);
while (pos != string::npos) {
if (!result[i+1]) {
result.insert(make_pair(i+1, make_pair(svec[i], rep_per_line)));
++result[i+1].second;
}
else {
++result[i+1].second;
}
}
}
return result;
}
void TextQuery::write_out(const string &word) {
cout << " The word " << "'" << word << "'" << " repeats:" << endl;
for (map< int, pair<string, int> >::const_iterator iter = result.begin(); iter != result.end(); ++iter) {
cout << "(line " << (*iter).first << " - " << (*iter).second.second << " times): ";
cout << result.second.first << endl;
}
}
这是程序的其余部分:
int main()
{
string word, ifile;
TextQuery tq;
cout << "Type in the file name: " << endl;
cin >> ifile;
ifstream infile(ifile.c_str());
tq.read_file(infile);
cout << "Type in the word want to search: " << endl;
cin >> word;
tq.find_word(word);
tq.write_out(word);
return 0;
}
谢谢你回答我的问题!!
I was trying to write a TextQuery program that allow user:
1. inputs a word
2. reads a file
3. prints out which lines the words appear and how many times the word appears on that line.
I created a class called "TextQuery" with 3 member functions:
1. "read_file" to read the file and return a reference to a vector
2. "find_word" to take the word needs to be searched
then returns a reference to a map< int, pair >
(the 1st 'int' is the line number, the 2nd 'int' is the number of times the word occurs on that line, the 'string' is the whole line)
3. "write_out" to write the result.
However, when I compiled the program I got this message:
/home/phongcao/C++/textquery_class_1.cc:21: error: invalid declarator before ‘&’ token
I just wonder how can the declarator wrong? Here is the class definition section:
#include <iostream>
#include <fstream>
#include <algorithm>
#include <map>
#include <vector>
#include <string>
using namespace std;
class TextQuery {
public:
vector<string> &read_file(ifstream &infile) const;
map< int, pair<string, int> > &find_word(const string &word) const;
void write_out(const string &word) const;
private:
vector<string> svec;
map< int, pair<string, int> > result;
}
//The following line is line 21, where I got the error!!
vector<string> &TextQuery::read_file(ifstream &infile) const {
while (getline(infile, line)) {
svec.push_back(line);
}
return svec;
}
map< int, pair<string, int> > &TextQuery::find_word(const string &word) const {
for (vector<string>::size_type i = 0; i != svec.end()-1; ++i) {
int rep_per_line = 0;
pos = svec[i].find(word, 0);
while (pos != string::npos) {
if (!result[i+1]) {
result.insert(make_pair(i+1, make_pair(svec[i], rep_per_line)));
++result[i+1].second;
}
else {
++result[i+1].second;
}
}
}
return result;
}
void TextQuery::write_out(const string &word) {
cout << " The word " << "'" << word << "'" << " repeats:" << endl;
for (map< int, pair<string, int> >::const_iterator iter = result.begin(); iter != result.end(); ++iter) {
cout << "(line " << (*iter).first << " - " << (*iter).second.second << " times): ";
cout << result.second.first << endl;
}
}
And here is the rest of the program:
int main()
{
string word, ifile;
TextQuery tq;
cout << "Type in the file name: " << endl;
cin >> ifile;
ifstream infile(ifile.c_str());
tq.read_file(infile);
cout << "Type in the word want to search: " << endl;
cin >> word;
tq.find_word(word);
tq.write_out(word);
return 0;
}
Thank you for answering my question!!
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类定义后缺少
;
。为什么会出现奇怪的错误消息?因为在该范围级别创建对象是完全合法的:
Missing
;
after the class definition.Why the weird error message? Because it's entirely legal to create an object at that level of scope:
还有其他错误 -
read_file
方法被声明为const
,因此您无法在其中调用非常量vector::push_back
(svec.push_back(line);
)There is other error -
read_file
method is declared asconst
, so you cannot call non-constantvector::push_back
inside it (svec.push_back(line);
)