Loop Imitations

[EsX_Raptor]

Hi!

As some of you may know, I'm currently learning C++ and would like to know something; I know that many of the loops in C/C++ can be represented using a regular while loop. In the following examples, please correct me if I'm wrong:

Representing a while-statement using a do-statement

do
{
     if (/* condition */) 
     {
          // ...
     }
     else
          break;
} while (true);

Representing a for-statement using a do-statement

int i = 0;
do
{
     if (i < MAX)
     {
          // ...
          i++;
     }
     else
          break;
} while (true);

Representing a while-statement using a for-statement

for (; /* condition */;)
{
     // ...
}

Representing a do-statement using a for-statement

// the statements go here...
for (; /* condition */;)
{
     // same statements as above...
}

These are my guesses at the moment. Please feel free to correct me if I happened to make a mistake in any of those or if you see that any of them are inefficient (say, if I included something that was not necessary and there is a better way to represent the same thing, etc.)

Thanks!

[Etherous]

Of course, any of these loops can be done using just 'if' and 'goto'. We have all these different loop structures because it makes it a little bit easier on the programmer

[ninja9578]

I think the most common loop that I use is

while(true){
   ...break;
}

and

for(unsigned int = 0; i < whatever; i++){

}

I really don't think there is a difference in performance, I think by the time they hit the abstract parse tree, they are the same. The only limitation that I can think of is that for loops and such are limited by the type that you use as the iterator.

[D_Drmmr]

Representing a do-statement using a for-statement

// the statements go here...
for (; /* condition */;)
{
     // same statements as above...
}

This way you have to write the same code twice. You can also write a do-loop as a for-loop and keep the body the same.

[GCDEF]

I think the most common loop that I use is

while(true){
   ...break;
}

and

for(unsigned int = 0; i < whatever; i++){

}

I really don't think there is a difference in performance, I think by the time they hit the abstract parse tree, they are the same. The only limitation that I can think of is that for loops and such are limited by the type that you use as the iterator.

while(true) isn't a really good habit to get into. It's better practice to put a condition in the while statement rather than rely on a break somewhere in the body.

[ninja9578]

I know, I do that whenever I can, but I've found myself recently having multiple situations that can break the loop, or I have code that has to be placed at the end of the loop that I don't want to run. Don't worry, I stress test it and make sure that there is no way for it to run infinately.

[laserlight]

while(true) isn't a really good habit to get into. It's better practice to put a condition in the while statement rather than rely on a break somewhere in the body.

Generally, I agree (though I prefer for (;;) ), but in some cases such a refactoring (particularly to convert to a do while loop) requires pulling out code into a function, which may be overkill.