A friend of mine told me that this code has some problems:
#include <iostream>
#include <cstdio>
using namespace std;
#define cout printf
int main(){
cout("cout");
}
He didn't give me the reason and asked me to figure it out which I couldn't. The code seems to be working fine, what could possibly be wrong with it?
As far as I know the Standard forbids defining names (with #define) declared in any standard library header.
Found this in n3290 ($17.6.4.3.1)
17.6.4.3.1 Macro names [macro.names]
1 A translation unit that includes a standard library header shall not #define or #undef names declared in any standard library header.
cout is hardly a keyword.
cout.#include <iostream> line, his program would be legal, just confusing. As of now, it needn't even compile.
<iostream> doesn't make it a valid program since it still includes cstdio.While you may argue that this code "seems to be working fine", consider a few years down the line when your 7-line source file is a 7-hundred-line source file and you are not the only maintainer.
You've moved on from writing C-style printf statements in C++ source files and you add (or another maintainer adds) the following line of perfectly valid C++:
cout << "What is wrong with my perfectly valid C++ code? " << endl;
And your compiler reports:
test.cpp:699: error: invalid operands of types ‘int ()(const char*, ...)’ and ‘const char [29]’ to binary ‘operator<<’
A whole world of pain!
Yes. It has problem.
Since its C++, one may habitually write cout << 1000 which would be an error in this case, but which is otherwise very normal in C++.
What next? Are you trying to define this:
#define scanf cin
//so that you can use it as
scanf >> variable; //not so kewl.
My advice is :
Don't try to change the meaning of such names. What will you get by doing so, after all? Nothing.
It's got maintenance problems, because you'd redefined well-known features to work differently. So no other programmer will want to work on this code.
Similar:
#define MULTIPLY(a, b) (a + b)
#define FIVE 12
#define THREE 3
int main(void)
{
return MULTIPLY(FIVE, THREE);
}
It gives the right answer, but is totally unmaintainable.
You have declared In C++ you don't have to main as returning int, but have not included a return statement. You should add a return 0; to the end of the main function.return a value from main, but it's good style.
Oh, and don't #define cout printf, it's really confusing. It may not be technically illegal, but it's not nice for whoever comes later to try to maintain your code.
coutto be an alias ofprintf. And the two are completely different animals.