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

Answer 1

It makes no effective difference when it comes to performance. Therefore I would use whichever is easier to understand in the context of the problem you are solving.

Answer 2

Great question. My answer: use type A ('<')

• You clearly see how many iterations you have (7).
• The difference between two endpoints is the width of the range
• Less characters makes it more readable
• You more often have the total number of elements i < strlen(s) rather than the index of the last element so uniformity is important.

Another problem is with this whole construct. i appears 3 times in it, so it can be mistyped. The for-loop construct says how to do instead of what to do. I suggest adopting this:

BOOST_FOREACH(i, IntegerInterval(0,7))

This is more clear, compiles to exaclty the same asm instructions, etc. Ask me for the code of IntegerInterval if you like.

Answer 3

The first is more idiomatic. In particular, it indicates (in a 0-based sense) the number of iterations. When using something 1-based (e.g. JDBC, IIRC) I might be tempted to use <=. So:

for (int i=0; i < count; i++) // For 0-based APIs

for (int i=1; i <= count; i++) // For 1-based APIs

I would expect the performance difference to be insignificantly small in real-world code.

Answer 4

I prefer:

for (int i = 0; i < 7; i++)

I think that translates more readily to "iterating through a loop 7 times".

I'm not sure about the performance implications - I suspect any differences would get compiled away.

Answer 5

As a slight aside, when looping through an array or other collection in .Net, I find

foreach (string item in myarray)
{
    System.Console.WriteLine(item);
}

to be more readable than the numeric for loop. This of course assumes that the actual counter Int itself isn't used in the loop code. I do not know if there is a performance change.

Answer 6

Way back in college, I remember something about these two operations being similar in compute time on the CPU. Of course, we're talking down at the assembly level.

However, if you're talking C# or Java, I really don't think one is going to be a speed boost over the other, The few nanoseconds you gain are most likely not worth any confusion you introduce.

Personally, I would author the code that makes sense from a business implementation standpoint, and make sure it's easy to read.