stupid program question

[Hugo716]

I'm reading a book on C++ and this is the first simple quiz question...

it says run this and guess what it does, now i know what it does but it wont compile.

#include <iostream>
int main();
{
    	int x = 5;
	int y = 7;
	cout "\n";
	cout << x + y << " " << x * y;
	cout "\n";
	return 0;
}

on DEV C++ it says - 3 C:\Documents and Settings\Reece.LAPTOP\Desktop\test.cpp expected unqualified-id before '{' token

3 C:\Documents and Settings\Reece.LAPTOP\Desktop\test.cpp expected `,' or `;' before '{' token

and on Visual C++ Express Edition it says

Compiling...
tester.cpp
.\tester.cpp(3) : error C2447: '{' : missing function header (old-style formal list?)
Build log was saved at "file://c:\Documents and Settings\Reece.LAPTOP\My Documents\Visual Studio 2005\Projects\tester\tester\Debug\BuildLog.htm"
tester - 1 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

can someone please just tell me whats wrong cuz its really winding me up because its soo simple.

[hk_mp5kpdw]

#include <iostream>
int main();  // Remove this semicolon
{
    int x = 5;
    int y = 7;
    std::cout << "\n";
    std::cout << x + y << " " << x * y;
    std::cout << "\n";
    return 0;
}

[Dave_Sinkula]

For now, add this.

#include <iostream>
using namespace std;
int main()//;
{
    	int x = 5;
	int y = 7;
	cout << "\n";
	cout << x + y << " " << x * y;
	cout << "\n";
	return 0;
}

And copy better.

[Hugo716]

Hmm, ok thanks. but why does the STD:: and deleting the ; work?

and using namespace std; doesnt work with it. get same error.


EDIT! using namespace std; worked with the << sorry, u didnt put the << till after

also, why the ; deleting?

[whiteflags]

Because int main(); is a function prototype, so all your code is ignored. Not that typing it is a problem: I see no reason why this wouldn't compile:

#include <iostream> 
int main(void); // but it is a waste of kestrokes

int main(void) {
    int x = 5, y = 7;
    std::cout << "\n";
    std::cout << x + y << " " << x * y;
    std::cout << "\n";
    return 0;
}

std is a namespace that all standard templates, objects, and functions are in. This needs to be explicitly declared, or you must say you are using the namespace std.

[Hugo716]

yeh it works as STD::

i am used to using int main(); as i normaly add namespace std; but i didnt think to this time.

sorry for posting a stupid thing like this.

Hugo.

[Hugo716]

another one. giving me the same error about missing function header for thr '{'

#include <iostream>
using namespace std;
// Function demonstration function
// prints out a usefull message

void DemonstrationFunction()
{
	cout<<"In Demonstration Function\n";

}
// Function main - prints out a message, then
// calls DemonstrationFunction, then prints out
// a second message
int main();
{
	cout<<"In Main\n";
	DemonstrationFunction();
	cout<<"Back in main\n";
	system("PAUSE");
	return 0;
}

really bugging me. sorry. thanks.

[Richie T]

int main();
{
	cout<<"In Main\n";
	DemonstrationFunction();
	cout<<"Back in main\n";
	system("PAUSE");
	return 0;
}

You were just told about this!

[Hugo716]

sorry just fixed it.

yeh but the last one worked WITH ; in it still. and they said it would work with ; as long as i added namespace

[whiteflags]

There is the excepton that you called system without including stdlib.h. That being said, calling system is the worst way to do a lot of things.

The program pauses for input only, so just use a standard input function to pause the program, like cin.get() or something.

[swgh]

EOF means end of file

putting a semi-colon after the main function is just asking for trouble.
Look at this...

#include <iostream>

using std::cout;
using std::endl;

// function prototypes
void func ( void );
void funct2 ( void );  // it is ok to end function prototypes with a semi=colon

int main ( void );  // this is an error
{
func(); // function calls end with a semi-colon

return 0;

cin.get();
}

void func ( void ); // this is an error
{
func2();
}

void func2 ( void ); // so is this
{
}

in general. NEVER place a semicolon after function title implementation.
ONLY include a semi-colon after a function prototype and when you call a function

Hope this helps -pete

[jafet]

You'll need to understand the difference between a function DECLARATION and a function DEFINITION. A declaration simply asserts that a function exists and is ready for use.

int main(int, char**);

So you can use main() although you haven't defined it's contents (although calling main() is a VERY BAD IDEA™). But to really compile your code, you'll need to define what main() does. This is the definition, which does not include the semicolon to differentiate it from a declaration:

int main(int n, char **v)
{
    std::cout << "Hello World!\n";
    std::cin.get();
}