请教一个关于重载运算符的模板函数的问题
这是 出错提示 :[root@localhost library]# g++ -o library library.cpp
library.cpp: In function `std::ostream& operator < <(std::ostream&, const std::list <T, std::allocator <_CharT> > &) ':
library.cpp:125: error: expected `; ' before "ref "
library.cpp:126: error: `ref ' undeclared (first use this function)
library.cpp:126: error: (Each undeclared identifier is reported only once for each function it appears in.)
library.cpp: In function `std::ostream& operator < <(std::ostream&, const std::list <T, std::allocator <_CharT> > &) [with T = Author] ':
library.cpp:146: instantiated from here
library.cpp:125: error: dependent-name ` std::list <T,std::allocator <_CharT> > ::iterator ' is parsed as a non-type, but instantiation yields a type
library.cpp:125: note: say `typename std::list <T,std::allocator <_CharT> > ::iterator ' if a type is meant
library.cpp: In function `std::ostream& operator < <(std::ostream&, const std::list <T, std::allocator <_CharT> > &) [with T = Patron] ':
library.cpp:150: instantiated from here
library.cpp:125: error: dependent-name ` std::list <T,std::allocator <_CharT> > ::iterator ' is parsed as a non-type, but instantiation yields a type
library.cpp:125: note: say `typename std::list <T,std::allocator <_CharT> > ::iterator ' if a type is meant
下面是我的源代码:
#include <iostream>
#include <string>
#include <list>
#include <algorithm>
using namespace std;
class Patron; // forward declaration;
class Book {
public:
Book() {
patron = 0;
}
bool operator== (const Book& bk) const {
return strcmp(title,bk.title) == 0;
}
private:
char *title;
Patron *patron;
ostream& printBook(ostream&) const;
friend ostream& operator < < (ostream& out, const Book& bk) {
return bk.printBook(out);
}
friend class CheckedOutBook;
friend class Patron;
friend void includeBook();
friend void checkOutBook();
friend void returnBook();
};
class Author {
public:
Author() {
}
bool operator== (const Author& ar) const {
return strcmp(name,ar.name) == 0;
}
private:
char *name;
list <Book> books;
ostream& printAuthor(ostream&) const;
friend ostream& operator < < (ostream& out,const Author& ar) {
return ar.printAuthor(out);
}
friend void includeBook();
friend void checkOutBook();
friend void returnBook();
friend class CheckedOutBook;
friend class Patron;
};
class CheckedOutBook {
public:
CheckedOutBook(list <Author> ::iterator ar = 0,
list <Book> ::iterator bk = 0) {
author = ar;
book = bk;
}
bool operator== (const CheckedOutBook& bk) const {
return strcmp(author-> name,bk.author-> name) == 0 &&
strcmp(book-> title,bk.book-> title) == 0;
}
private:
list <Author> ::iterator author;
list <Book> ::iterator book;
friend void checkOutBook();
friend void returnBook();
friend class Patron;
};
class Patron {
public:
Patron() {
}
bool operator== (const Patron& pn) const {
return strcmp(name,pn.name) == 0;
}
private:
char *name;
list <CheckedOutBook> books;
ostream& printPatron(ostream&) const;
friend ostream& operator < < (ostream& out, const Patron& pn) {
return pn.printPatron(out);
}
friend void checkOutBook();
friend void returnBook();
friend class Book;
};
list <Author> catalog[ 'Z '+1];
list <Patron> people[ 'Z '+1];
ostream& Author::printAuthor(ostream& out) const {
out < < name < < endl;
list <Book> ::const_iterator ref = books.begin();
for ( ; ref != books.end(); ref++)
out < < *ref; // overloaded < <
return out;
}
ostream& Book::printBook(ostream& out) const {
out < < " * " < < title;
if (patron != 0)
out < < " - checked out to " < < patron-> name; // overloaded < <
out < < endl;
return out;
}
ostream& Patron::printPatron(ostream& out) const {
out < < name;
if (!books.empty()) {
out < < " has the following books:\n ";
list <CheckedOutBook> ::const_iterator bk = books.begin();
for ( ; bk != books.end(); bk++)
out < < " * " < < bk-> author-> name < < ", "
< < bk-> book-> title < < endl;
}
else out < < " has no books\n ";
return out;
}
template <typename T>
ostream& operator < < (ostream& out, const list <T> & lst) {
list <T> ::iterator ref;
for (ref = lst.begin(); ref != lst.end(); ref++)
out < < *ref; // overloaded < <
return out;
}
char* getString(char *msg) {
char s[82], i, *destin;
cout < < msg;
cin.get(s,80);
while (cin.get(s[81]) && s[81] != '\n '); // discard overflowing
destin = new char[strlen(s)+1]; // characters;
for (i = 0; destin[i] = toupper(s[i]); i++);
return destin;
}
void status() {
register int i;
cout < < "Library has the following books:\n\n ";
for (i = 'A '; i <= 'Z '; i++)
if (!catalog[i].empty())
cout < < catalog[i];
cout < < "\nThe following people are using the library:\n\n ";
for (i = 'A '; i <= 'Z '; i++)
if (!people[i].empty())
cout < < people[i];
}
[解决办法]
typename list <T> ::iterator ref;
[解决办法]
template <typename T>
ostream& operator < < (ostream& out, const list <T> & lst) {
list <T> ::iterator ref;
改为:
template <typename T>
ostream& operator < < (ostream& out, const list <T> & lst) {
list <T> ::const_iterator ref;
