i is for index. j is simply the next letter and we’re too lazy to think up something meaningful
jndex
kndex
lndex
When I’m doing coding interviews I always like to start off and say I’m a big fan of very long variable names. “As descriptive as you can be” I say. Then I get to my first for loop. Instead of i I use “iterator” and then when I start a nested loop I use “jiterator” and it always gets a laugh.
It depends.
x
andy
are either elements or coordinates,a
andb
usually elements though in e.g. Haskell reserved (by convention) for type variables.The
i
j
k
l
series is reserved for indices.n
m
etc. are the counts of something, as such you’ll seei
counting up ton
. Both are due to mathematical sum notation and general mathematical convention. Random google result:Let x1, x2, x3, …xn denote a set of n numbers. x1 is the first number in the set. xi represents the ith number in the set.
…if you’re using a language in which you use
i
often chances are you should stop coding in C and get yourself a language with iterators. Manual loops are a bug magnet.I used starcraft references in mine till the project lead demanded I knock it off.
The protoss quotes were perfect.
People who name iterators with one letter have no soul.
And people who iterate over 3D space using firstDimensionIndex, secondDimensionIndex, and thirdDimensionIndex instead of x, y, z have no sense 😜
x, y, and z are absolutely fine for spatial addressing.
A useful tip I picked up was to use
ii
instead ofj
for an inner loop. It’s far more distinct thanj
.If for some terrible reason you have even more inner loops you can easily continue the trend
i
,ii
,iii
,iiii
,iiiii
- oriv
,v
if you’re feeling romanWhen you have multiple indices you’re also bound to have multiple cardinals those indices count up to, say
foo.length
andbar.length
, sofoo_i
andbar_i
are perfectly legible and self-documenting. A bit Hungarian but Hungarian is good in small amounts. Unless you’re dealing withwidth
andheight
in which case it’sx
andy
but it’s not thatwidth_i
would be incomprehensible.