Templates and context reasoning

It seems to be true that a concept is not really understood until it is applied.

/* 
Lecture 16 
Programming Abstractions
Templates
examples of usage
*/
#include <cstdlib> //also exit
#include <string>
#include <fstream>
#include <sstream>
#include <iostream>
#include <vector>
#include <cmath>
using namespace std;

template <typename Type>
void Swap( Type &one, Type &two)
{
Type tmp=one;
one=two;
two=tmp;
}

/* Doesn't work for vector type 
because cout can't deal with
composite variable. */
template <typename T>
void PrintVector(vector<T> &v)
{
 for (unsigned int i=0;i<v.size();i++){
//  cout<< v[i] <<" ";
 }
 cout<<endl;
}

struct coordT 
{
double x , y ; 
};

void AnError(string mesg)
{
 cerr<<mesg<<endl;
 exit(0);
}
int main() 
{
string estr="There was no error";
float f,g;
f=1.1;g=2.2;
Swap(f,g);
cout<<"Float "<<f<<" "<<g<<endl;
int a,b;
a=1;b=2;
string s,t;
s="123";t="456";
Swap(a,b);
cout<<"Int "<<a<<" "<<b<<endl;
Swap(s,t);
cout<<"String "<<s<<" "<<t<<endl;

vector<coordT> c;
PrintVector(c);

AnError(estr);
return 0;
}