c++ - error LNK2019: unresolved external symbol error?

Can any1 tell me why I'm getting this error.

template header file (prog.h):

#include 
#include 

#include 
#include 
#include  
using namespace std;

#ifndef H_PROG
#define H_PROG

// data files


#define D1 "data1.txt"

#define INT_SZ 4    // width of integer
#define FLT_SZ 7    // width of floating-pt number
#define STR_SZ 12   // width of string

#define INT_LN 15   // no of integers on single line
#define FLT_LN 9    // no of floating-pt nums on single line
#define STR_LN 5    // no of strings on single line


// function and class prototypes

// stores items from input file into vector
template < class T > 
void get_list ( vector < T >&, const char* );

#endif

.cpp file :

#include "prog.h"
#include 


template < class T >
void get_list ( vector < T >& vector1, const char* filename )
{
    ifstream infile;
    ofstream outfile;


    infile.open(filename);
    if(infile.fail())
    {
        cout<<"File did not open."<    }
    else
    {
        T data;
        while(infile)

        {
            infile>>data;
            vector1.insert(data);
        }
    }
}

in the main function I have :

#include "prog.h"
#include 

int main ( )
{
    vector < int >    v1;  
    vector < float >  v2;   
    vector < string > v3;  



    // first heap

    cout << "first heap - ascending order:\n\n";
    get_list(v1,D1);

    _getch();
    return 0;
}

---

when i try to run this i get an error saying :

error LNK2019: unresolved external symbol "void __cdecl get_list(class std::vector > &,char const *)" (??$get_list@H@@YAXAAV?$vector@HV?$allocator@H@std@@@std@@PBD@Z) referenced in function _main