slamit93

last question that I am not sure how to answer on my study guide:

When should a while loop be used and when should a for loop be used?

In my understanding, they basically do the exact same thing, and I can pretty much write either type of loop to do the exact same thing... I guess, is it just preferential to use a for loop when you only want the loop to go through a certain number of iterations, and you should use a while loop when you just want a particuliar condition to be met for the loop to keep running?

Da-Spit

Well I guess it's just a matter of preferance, since a while loop can do almost anything a for loop can. All you have to do is:
And that would work just as well as a for loop.. wouldn't it? I'f I'm wrong could somebody please correct me.

Sebastiani

Really it's just a matter of preference.

For loops handle: initialize, condition, post-assignment(usually incrementing)

While loops just handle condition and often post-assignment.


int i;

for( i = 0; i < 10; i++)
{
//...do
}


int i = 0;

while(i < 10)
{
//...do
i++;
}


Sometimes the incrementation takes place in the condition part of the while loop, but be careful, often the incrementation takes place first so that:

int i = 0;

while(i++ < 10) //...i = 1 before entering loop! As if ++i !!
{
//...do
}

...must be rewritten:

int i = -1;

while(i++ < 10) //...i = 0 before entering loop! As if ++i .
{
//...do
}


...this may depend on your compiler, though...

Often the incrementation is done on a variable being worked on, and the above problem does not occur:

int variable[10];
int i = 0;

while(i < 10)
{
variable[i++] = i; //...no problem
}



Incidentally, a while loop written as a for loop would be:



int i = -1; //...to avoid side-effect problem...

for( ; i++ < 10; )
{
//...do
}

Magos

If you are going to iterate a known number of times, you should use a for loop.

If you don't know how many times you are going to loop, but know that it is at least 1, you should use a do-while loop.

If you don't know how many times you are going to loop, and it might not even be 1 loop, you should use a while loop.

As has been pointed out, you could use one 'loop-type' to do what the other do with a little tweaking and clever layout, but these are the general purposes.

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