I have found the following loop annotation in a big project I am working on (pse

Question

I have found the following loop annotation in a big project I am working on (pseudocode):

What brought my attention is this extra "n" variable. I have never seen a for lop written in this way before.

Obviously in this scenario there is no reason why this code couldn't be written in the following way (which I'm very much used to):

But it got me thinking.

Is there a scenario when writing such a for loop would make sense? The idea comes to mind that "array" length may change during the for loop execution, but we don't want to loop further than the original size, but I can't imagine such a scenario.

Shrinking the array inside the loop does not make much sense either, because we are likely to get OutOfBoxException.

Is there a known design pattern where this annotation is useful?

Explanation / Answer

The variable n ensures the generated code doesn't fetch the array length for every iteration.

It's an optimization that might make a difference in run time depending on the language used, whether the array is actually a collection object or a JavaScript "array", and other optimization details.

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.