Should one use < or <= in a for loop [closed]

Answer 1

I think either are OK, but when you've chosen, stick to one or the other. If you're used to using <=, then try not to use < and vice versa.

I prefer <=, but in situations where you're working with indexes which start at zero, I'd probably try and use <. It's all personal preference though.

Answer 2

Both of those loops iterate 7 times. I'd say the one with a 7 in it is more readable/clearer, unless you have a really good reason for the other.

Answer 3

Seen from an optimizing viewpoint it doesn't matter.

Seen from a code style viewpoint I prefer < . Reason:

for ( int i = 0; i < array.size(); i++ )

is so much more readable than

for ( int i = 0; i <= array.size() -1; i++ )

also < gives you the number of iterations straight away.

Another vote for < is that you might prevent a lot of accidental off-by-one mistakes.

Answer 4

I have always preferred:

for ( int count = 7 ; count > 0 ; -- count )

Answer 5

As people have observed, there is no difference in either of the two alternatives you mentioned. Just to confirm this, I did some simple benchmarking in JavaScript.

You can see the results here. What is not clear from this is that if I swap the position of the 1st and 2nd tests, the results for those 2 tests swap, this is clearly a memory issue. However the 3rd test, one where I reverse the order of the iteration is clearly faster.

Answer 6

I'd say use the "< 7" version because that's what the majority of people will read - so if people are skim reading your code, they might interpret it wrongly.

I wouldn't worry about whether "<" is quicker than "<=", just go for readability.

If you do want to go for a speed increase, consider the following:

for (int i = 0; i < this->GetCount(); i++)
{
  // Do something
}

To increase performance you can slightly rearrange it to:

const int count = this->GetCount();
for (int i = 0; i < count; ++i)
{
  // Do something
}

Notice the removal of GetCount() from the loop (because that will be queried in every loop) and the change of "i++" to "++i".