What is an ideal variable naming convention for loop variables? [closed]

Answer 1

for numerical computations, matlab, and the likes of it, dont use i, j

these are reserved constants, but matlab wont complain.

My personal favs are

index first,second counter count

Answer 2

i

if I have a nested loop then also j.

This convention is so common that if you manage to come across a variable i in a block of code that you can't see the start of you still instantly recognise it for what it is.

Answer 3

I use single letters only when the loop counter is an index. I like the thinking behind the double letter, but it makes the code quite unreadable.

Answer 4

My experience is that most people use single letters, e.g.: i, j, k, ... or x, y, or r, c (for row/column) or w, h (for width/height) , etc.

But I learned a great alternative a long time ago, and have used it ever since: double letter variables.

// recommended style              ●    // "typical" single-letter style
                                  ●
for (ii=0; ii<10; ++ii) {         ●    for (i=0; i<10; ++i) {
    for (jj=0; jj<10; ++jj) {     ●        for (j=0; j<10; ++j) {
        mm[ii][jj] = ii * jj;     ●             m[i][j] = i * j;
    }                             ●        }
}                                 ●    }

In case the benefit isn't immediately obvious: searching through code for any single letter will find many things that aren't what you're looking for. The letter i occurs quite often in code where it isn't the variable you're looking for.

Answer 5

I've started to use context-relevant loop variable names mixed with hungarian.

When looping through rows, I'll use iRow. When looping through columns I'll use iCol. When looping through cars I'll use iCar. You get the idea.

Answer 6

I have long used the i/j/k naming scheme. But recently I've started to adapt a more consequent naming method.

I allready named all my variables by its meaning, so why not name the loop variable in the same deterministic way.

As requested a few examples:

If you need to loop trough a item collection.

for (int currentItemIndex = 0; currentItemIndex < list.Length; currentItemIndex++)
{
    ...
}

But i try to avoid the normal for loops, because I tend to want the real item in the list and use that, not the actual position in the list. so instead of beginning the for block with a:

Item currentItem = list[currentItemIndex];

I try to use the foreach construct of the language. which transforms the.

for (int currentItemIndex = 0; currentItemIndex < list.Length; currentItemIndex++)
{
    Item currentItem = list[currentItemIndex];
    ...
}

into

foreach (Item currentItem in list)
{
   ...
}

Which makes it easier to read because only the real meaning of the code is expressed (process the items in the list) and not the way we want to process the items (keep an index of the current item en increase it until it reaches the length of the list and thereby meaning the end of the item collection).

The only time I still use one letter variables is when I'm looping trough dimensions. But then I will use x, y and sometimes z.