I'm trying to do 11 exercise at the end of Chapter 5.9 Bjarne Stroustrup The C++ Programming Language.
1 #include <iostream>
2 #include <string>
3 #include <vector>
4 #include <algorithm>
5
6 void print(std::vector<std::string>::const_iterator str) {
7 std::cout << *str;
8 }
9
10 int main(void) {
11 std::vector<std::string> words;
12 std::string tmp;
13
14 std::cin >> tmp;
15 while (tmp != "Quit") {
16 words.push_back(tmp);
17 std::cin >> tmp;
18 }
19
20 for_each(words.begin(), words.end(), print);
21
22 return 0;
23 }
When I uncomment 20 line I get this error:
In file included from /usr/include/c++/4.7/algorithm:63:0,
from 5.9.11.cpp:4:
/usr/include/c++/4.7/bits/stl_algo.h: In instantiation of ‘_Funct std::for_each(_IIter, _IIter, _Funct) [with _IIter = __gnu_cxx::__normal_iterator<std::basic_string<char>*, std::vector<std::basic_string<char> > >; _Funct = void (*)(__gnu_cxx::__normal_iterator<const std::basic_string<char>*, std::vector<std::basic_string<char> > >)]’:
5.9.11.cpp:20:44: required from here
/usr/include/c++/4.7/bits/stl_algo.h:4442:2: error: could not convert ‘__first.__gnu_cxx::__normal_iterator<_Iterator, _Container>::operator*<std::basic_string<char>*, std::vector<std::basic_string<char> > >()’ from ‘std::basic_string<char>’ to ‘__gnu_cxx::__normal_iterator<const std::basic_string<char>*, std::vector<std::basic_string<char> > >’
Compile command :
g++ prog.cpp -o prog -Wall
What i did wrong?
The callback function should take an std::string, not an iterator. for_each passes each element itself. Thus, your function would become:
void print(const std::sting &str) {
std::cout << str << ' '; //note I separated the words
}
For a fixed example (including the std:: on for_each, as well as a couple other minor differences), see this run.
In C++11 (accessible to your compiler through -std=c++0x or -std=c++11), you need not even worry about std::for_each to loop through the container because C++11 introduced the ranged-for loop:
for (const std::string &str : words)
std::cout << str << ' ';