Programming Forums > Application Development > C++

Broax · Jul 24th, 2005, 11:45 AM

Could someone tell me what is the practical diference between while and do while? I know that in while the condition is evaluated before the statment as in the do while it is evaluated at the end.

But in my (very) limited programming experience I don't know where these diferente cases apply...

Thanks...

OpenLoop · Jul 24th, 2005, 11:54 AM

(Toggle Plain Text)

int x = 5;
while(x-- > 1)
{
  cout<<x;
}  //prints 4,3,2,1

cout<<endl;
x = 5;

do
{
  cout<<x;
}while(x-->1);   //prints 5,4,3,2,1

stevengs · Jul 24th, 2005, 12:00 PM

Quote:

Originally Posted by Broax

Could someone tell me what is the practical diference between while and do while?

do while always performs the action at least once. while checks the condition first, so it may not perform the action at all.

do while = [act�on]+
while = [action]*

Broax · Jul 24th, 2005, 12:13 PM

Yes... I get it now, but is there any situatuin where while can be used and do while can't? (or the other way around?)

stevengs · Jul 24th, 2005, 12:21 PM

Quote:

Originally Posted by Broax

Yes... I get it now, but is there any situatuin where while can be used and do while can't? (or the other way around?)

there is really nothing more to it. You can manipulate the conditions as you please, and substitute one for the other.

Broax · Jul 24th, 2005, 12:34 PM

hmmm... I see!

Thanks for the help, then!

I'll get back to german studying and later back to c++!

Ancient Dragon · Jul 24th, 2005, 1:14 PM

well, one example when I would use do while instead of while is for interating through the file system using _findfirstfile() and _findnextfile(), or equivalent os-specific functions. The _findfirstfile() locates the first file, so the end of the do-while would be the _findnextfile().

(Toggle Plain Text)

_findfirstfile()
do {
  // blabla
} while( _findnextfile() );

coding the above with while loop would be more problematic.

Jul 24th, 2005, 11:45 AM	#1
Broax Hobbyist Programmer Join Date: Jan 2005 Location: Porto, Portugal Posts: 142 Rep Power: 4	while/do while? Could someone tell me what is the practical diference between while and do while? I know that in while the condition is evaluated before the statment as in the do while it is evaluated at the end. But in my (very) limited programming experience I don't know where these diferente cases apply... Thanks... __________________ PORTUGALPORTUGA PORTUGALPORTUGA PORTUGALPORTUGA PORTUGALPORTUGA PORTUGALPORTUGA

Jul 24th, 2005, 11:54 AM	#2
OpenLoop Expert Programmer Join Date: May 2005 Location: East Lansing, MI Posts: 663 Rep Power: 4	(Toggle Plain Text) int x = 5; while(x-- > 1) { cout<<x; } //prints 4,3,2,1 cout<<endl; x = 5; do { cout<<x; }while(x-->1); //prints 5,4,3,2,1 int x = 5; while(x-- > 1) { cout<<x; } //prints 4,3,2,1 cout<<endl; x = 5; do { cout<<x; }while(x-->1); //prints 5,4,3,2,1

Jul 24th, 2005, 12:13 PM	#4
Broax Hobbyist Programmer Join Date: Jan 2005 Location: Porto, Portugal Posts: 142 Rep Power: 4	Yes... I get it now, but is there any situatuin where while can be used and do while can't? (or the other way around?) __________________ PORTUGALPORTUGA PORTUGALPORTUGA PORTUGALPORTUGA PORTUGALPORTUGA PORTUGALPORTUGA

Jul 24th, 2005, 12:34 PM	#6
Broax Hobbyist Programmer Join Date: Jan 2005 Location: Porto, Portugal Posts: 142 Rep Power: 4	hmmm... I see! Thanks for the help, then! I'll get back to german studying and later back to c++! __________________ PORTUGALPORTUGA PORTUGALPORTUGA PORTUGALPORTUGA PORTUGALPORTUGA PORTUGALPORTUGA

Jul 24th, 2005, 1:14 PM	#7
Ancient Dragon PFO God In Training Join Date: Jun 2005 Location: near St Louis, MO. (USA) Posts: 546 Rep Power: 4	well, one example when I would use do while instead of while is for interating through the file system using _findfirstfile() and _findnextfile(), or equivalent os-specific functions. The _findfirstfile() locates the first file, so the end of the do-while would be the _findnextfile(). (Toggle Plain Text) _findfirstfile() do { // blabla } while( _findnextfile() ); _findfirstfile() do { // blabla } while( _findnextfile() ); coding the above with while loop would be more problematic.

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Programming Forums > Application Development > C++

while/do while?