Thread: My first game

Originally Posted by Thantos

Code:

using namespace std;

brings the entire std namespace into the global namespace

Code:

using std::cout;

brings only std::cout into the global namespace


A lot. Here are two code segments that would not work with the above macro:

Code:

std::cout<<"Hello world"<<std::endl;
mynamespace::<<cout<<"Hello world"<<mynamespace::endl;

That's when you go like this:

Code:

#define JLKJSDFKJER std::cout
JLKJSDFKJER << "Much better *eats caviar*";

The drawback is that you have to cut and paste lol. But then again maybe it's better if you just went std::cout...

Originally Posted by sean_mackrory

You'd also get problems if you ever used cout in a string... though I wonder how likely that is to happen...

String literals aren't parsed for macros

Originally Posted by Thantos

A lot. Here are two code segments that would not work with the above macro:

Code:

std::cout<<"Hello world"<<std::endl;
mynamespace::<<cout<<"Hello world"<<mynamespace::endl;

Wouldn't the first one compile with the macro?

Code:

cout<<"Hello World"<<std:endl;

and does the second one even compile? That looks rough...care to explain it?

Opps small typo in the second one. Should have been:

Code:

mynamespace::cout<<"Hello world"<<mynamespace::endl;

To show you exactly what happens lets take the following program:

Code:

#include <iostream>
//#define cout std::cout
namespace mynamespace
{
  std::ostream& endl (std::ostream& o)
  {
    return o<<'\n'<<std::flush;
  }

  std::ostream& cout = std::cout;
};


int main()
{
  std::cout<<"Hello world"<<std::endl;
  mynamespace::cout<<"Hello world"<<mynamespace::endl;
}

This compiles and produces the expected results.
Nows lets comment the #include and uncomment the #define and tell gcc to do only the preprocesser work. Now our program looks like this:

Code:

namespace mynamespace
{
  std::ostream& endl (std::ostream& o)
  {
    return o<<'\n'<<std::flush;
  }

  std::ostream& std::cout = std::std::cout;
};


int main()
{
  std::std::cout<<"Hello world"<<std::endl;
  mynamespace::std::cout<<"Hello world"<<mynamespace::endl;
}

See the problem now?

cheers