标头C ++中带有STL的函数声明

Question

I am pretty new to the concept of splitting a program into header and etc. Normally, it goes ok, but in this case I have a whole bunch of errors if i try to do next:

Suppose I have a .cpp file:

#include <iostream>
#include <string>
#include <map>
#include <algorithm>
#include <vector>
#include "Header.h"
using namespace std;

int main() {
    //some code here
}

map <char, char> create(vector <char> &one, vector <char> &two) {
    //some code here
}

vector <char> conc(string phrase) {
    // some code here
} 

vector <char> result(vector<char> three, map <char, char> code) {
    // some code here
}

In Header.h I have:

map <char, char> create(vector <char> &one, vector <char> &two);
vector <char> conc(string phrase);
vector <char> result(vector<char> three, map <char, char> code);

Which are just function declarations.. If I put them in .cpp the program works great, but if in Header.h - it does not. Could you, please tell what I am missing here?

I am reading about the concept of splitting on cprogramming.com, but they never had an example with STL. Thank you!

Answer 1

You use using namespace std; in cpp file, but not in header (and don't use it in header), so you should use fully qualified type names:

#ifndef HEADER_H
#define HEADER_H

#include <string>
#include <map>
#include <vector>

std::map <char, char> create(std::vector <char> &one, std::vector <char> &two);
std::vector <char> conc(std::string phrase);
std::vector <char> result(std::vector<char> three, std::map <char, char> code);

#endif // HEADER_H

Answer 2

This is mostly an educated guess since you didn't post the actual error nor the whole code.

You're missing std:: before every STL class name since you should not use using statement in header files.

Example: std::map <char, char> create(std::vector <char> &one, std::vector <char> &two);

Also make sure you have the proper include statement at the top of your header file ( <vector> , etc...).