Question about std:string and std:cout

[zhege]

I am a beginner of C++;
I have a question about the std:string and std:cout class;

Two pieces of code:
--------------------------------
#include <iostream>
#include <string>
using namespace std;

int main()
{
string s1 = "Hii";
string s2 = "MSDN Fans!\n";
cout<<s1+s2;
}

---------------------------------

#include <iostream>
#include <string>
using namespace std;

int main()
{
string s1 = "Hii";
string s2 = "MSDN Fans!\n";
string s3 = s1 + s2;
cout<< s3;
}

Which one would be run faster or they'r totally the same.Is there any
method for measuring the efficiency of programs?

[Pete C]

zhege wrote:

I am a beginner of C++;
I have a question about the std:string and std:cout class;

Two pieces of code:
--------------------------------
#include <iostream>
#include <string>
using namespace std;

int main()
{
string s1 = "Hii";
string s2 = "MSDN Fans!\n";
cout<<s1+s2;
}

---------------------------------

#include <iostream>
#include <string>
using namespace std;

int main()
{
string s1 = "Hii";
string s2 = "MSDN Fans!\n";
string s3 = s1 + s2;
cout<< s3;
}

Which one would be run faster or they'r totally the same.Is there any
method for measuring the efficiency of programs?

Unless you have hard evidence that one is faster than the other, *and*
that this speed is critical to your program's performance, use the form
that is most expressive to you.

That was the most important thing. That said, in this instance the two
versions will probably be identical. In your first piece of code, the
compiler will construct an unnamed temporary object anyway.

For measuring performance, use a profiler. I use cachegrind on linux,
Rational Quantify on Windows or Intel's VTune on either.