Thread: for(;;) vs. while(true)

I don't think I've ever seen for(;;) in a real program... only in books. Not that I've studied that many real programs!

To me, while(true) just looks better!

I've seen this used with looping thru a menu for example
sort of like :

Code:

for (; ; ) ...                      
{ 
int choice = menu( );      
   switch(choice)              
   {
   case ( 1 ):
   some function( );
   break; 
   case ( 2 ):
   some other function();
   break;
   etc.
     etc.
       etc.

That way the break statements gets you out of the infinite loop &
you can go thru as many case statements as you want....
If you had quite a few choices "while (true)" would lead to a lengthy "If statement"
the infinite for(; ; ) loop lets you use a switch statement instead..

Hammer, when you say compile and see for myself, do you mean run it in a profiler or do you mean find some way to look at the assembly myself? And I'll check out that thread you're talking about

Using something like MSVC you can look at the ASM while debugging. There are many compiler products that offer this feature.

the infinite for(; ; ) loop lets you use a switch statement instead..

You know what, so does a while loop.

Hopefully your compiler would optimize the two to the same thing.

While(1) because im lazy and dont want to type true. When i read it outloud i always say "Loop Forever". I dont think there should be any major difference between while(1) and for(;. true is just an enumeration of 1 isnt it? A literal 1? or am i mistaken...

Well yes you could you a switch statement in a while loop, but somebody said they had never seen a for(; ; ) loop used in a real program and someone wanted to see it used so they could discuss it with their teacher.....Actually with either it depends on how you code it.......Here is the full code with the snippet I posted earlier....A fellow over at source-forge wrote this for me..
The purpose of the example was to put as many examples of C++ code in one short snippet..... and I think he gave me 5 stars worth...........classes, reference, for(; ; ), whatever..it's in here...great learning example.........

Code:

 
// First, notice that the main() calls the function 'OperationWindow( )'
// that calls the 'menu()' and used in the switch within the 'OperationWindow( )' 
// function. 

// Note when 'n' is the choice for quit ?... the switch "re-calls" the 
// function 'OperationWindow( )' to start a new.

// Also in main(), a pointer to mainClass 'mainClass *openNewMain = new mainClass ;'
// and the using 'new' sets aside the space in memory.

// Last after the program ends, the 'delete openNewMain ; openNewMain = 0 ;'
// frees the memory... and then sets 'openNewMain = 0 ' so not to leave trash 
// in memory.

// Notice that no 'system("PAUSE")' has been added to the end of main().
// ********************************************************************
// This may not be world class programming, but I put a number of basic
// things to give an idea or two maybe.


#include<iostream>

class mainClass                    	
{                                  	
	public:                         
	mainClass( ){}			
	~mainClass( ){}                 

	int OperationWindow( );        
	void saldot ( );               
	void goback ( );               
	void endcall ( );              

	protected:

	int menu( );                   

};                                 


int mainClass::OperationWindow( )
{
bool nul_operation = false;
	for (;;)                       
	{                              
	int choice = menu( );          
	                               
	                               
	                               
	                               
	switch(choice)              
		{
		case ( 1 ):
		saldot( );
		break; 
		case ( 4 ):
		nul_operation = true; 
		std::cout << "Quit Y-OR-N ? ";
		char con; std::cin >> con;
		if(con == 'y' || con == 'Y'){}
		else OperationWindow( ); 
  		break; 
		default:
		goback( );
		break;
		} 
		if ( nul_operation )
		break;
	}
}


int mainClass::menu( )
{
int choice;

std::cout << "\n mainClass Demo\n";
std::cout << "(Enter (1)> The only Choice !.\n";
std::cout << "(Enter (4)> Quit.\n\n";
std::cout << "|Here> ";
std::cin >> choice;

return choice;
OperationWindow( );     
}

void mainClass::saldot( ) 
{
system("CLS");
std::cout <<"\n What ? ... Press Any Key to continue"<<"\n";
system("PAUSE > NUL");
}

void mainClass::goback( ) 
{
system("CLS"); 
std::cout <<"\nNot a selection... try again ... Press Any Key to continue"<<"\n";
system("PAUSE > NUL");
} 

void mainClass::endcall( ) 
{
system("CLS");
std::cout <<"\n!!! A Request to close this program has been made ... close ?"<<"\n";
system("PAUSE > NUL");
}


int main( )
{
mainClass *openNewMain = new mainClass ;

openNewMain->OperationWindow( );
delete openNewMain ; openNewMain = 0 ;

return 0;
}



//j@ck_

Heh !
This all started over How to make a counsel app stay up without using system("pause") or getch() or cin.get() etc.

and then sets 'openNewMain = 0 ' so not to leave trash in memory.

You should set it to NULL not 0. The only thing that this actually does is prevents you from accidently dereferencing a pointer that isn't pointing anywhere. The compiler should pick up the error.

It is also worth reading this link.