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I'm trying to learn templates and I've run into this confounding error. I'm declaring some functions in a header file and I want to make a separate implementation file where the functions will be defined.
Here's the code that calls the header (dum.cpp):
#include <iostream>
#include <vector>
#include <string>
#include "dumper2.h"
int main() {
std::vector<int> v;
for (int i=0; i<10; i++) {
v.push_back(i);
}
test();
std::string s = ", ";
dumpVector(v,s);
}
Now, here's a working header file (dumper2.h):
#include <iostream>
#include <string>
#include <vector>
void test();
template <class T> void dumpVector(const std::vector<T>& v,std::string sep);
template <class T> void dumpVector(const std::vector<T>& v, std::string sep) {
typename std::vector<T>::iterator vi;
vi = v.cbegin();
std::cout << *vi;
vi++;
for (;vi<v.cend();vi++) {
std::cout << sep << *vi ;
}
std::cout << "\n";
return;
}
With implementation (dumper2.cpp):
#include <iostream>
#include "dumper2.h"
void test() {
std::cout << "!olleh dlrow\n";
}
The weird thing is that if I move the code that defines dumpVector from the .h to the .cpp file, I get the following error:
g++ -c dumper2.cpp -Wall -Wno-deprecated
g++ dum.cpp -o dum dumper2.o -Wall -Wno-deprecated
/tmp/ccKD2e3G.o: In function `main':
dum.cpp:(.text+0xce): undefined reference to `void dumpVector<int>(std::vector<int, std::allocator<int> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >)'
collect2: ld returned 1 exit status
make: *** [dum] Error 1