i and j insteadusing x and y ?

[Ralf]

since i am coding, i have ever used variables like following examples:

Code: Select all

for y = 0 to  480
  for x = 0 to 640
     ..code...
  next
next


for i = 0 to 100
  .. code...
next

but now when i study the web i found even more examples where people using i and j instead x and y... are i and j something like a stanard as used in following example? (i know, i could use any variable)

for j = 0 to  480     ; seems j stands for y in java/c/c++ !?
  for i = 0 to 640     ; seems i stands for x in jave/c/c++ !?
     ..code...
  next
next

[dell_jockey]

Moin Ralf,

if you're iterating through a 2D picture space, using 'x' and 'y' makes perfectly sense.
I once read something about early programming days, where programmers couldn't really type with ten fingers. 'I' and 'J' were (and still are) close together on the keyboard and require only a single finger to type... If this is folklore or truth, I don't know, but is funny nonetheless.

Generally, give variables meaningful names, even those that are used as a counter in a loop. In two years' time, you still want to be able to read the code you wrote yourself, so make it clear what you intended. If you intend to distribute the code, it's even more important to clearly convey your intentions.

Tschüß

[PB]

In mathematics, X and Y have always been for left-right and up-down, and
Z is used for in-out (for 3D applications). I've never heard of I and J before.

[freak]

I think the 'i' as a counter variable comes from 'index', but i'm not really sure about that.
My first ever book on programming (quickbasic ) also used an 'i' in the examples
and i am still doing that today.

Some things are hard to change

[blueb]

I seem to remember 'i' stood for integer, because most loops were used as counters.


--blueb

[dell_jockey]

Using 'i' for index counting is common indeed. However, it doesn't hurt to let the reader of your code know what it is, that you're counting there, so I recommend that you give these variables meaningful names as well. After all, one future day, you yourself might be that reader...

[Ralf]

@dell_jockey: very interested... sure, i always try to use clear and selfexplained variables as long as i dont do any X,Y,Z stuff

@PB: You are right about the X,Y,Z - i thougt so too all the time! but there are really some sources on the web, wehre they use i and j for 2D operations too. It confused me a bit!

@freak: handshake! I use 'i' too for normal loops since i am coding!

@blueb: yes, i heared something about that some years ago! i stands for integer. If you do any 2D drawings, using Int would make sence but i was still wondering why the do not use something like iX iY !?

I use for all variables the first upper sign of its type and then its name! This makes coding for me much more easy and the source 1000 times more readable! For example:

Code: Select all

lRed = Point(x,y)                 ;   red is a long variable
dEastern = DIM name(x,y)   ;   Eastern is a DIM (normaly d = double)
fBeer = 2                            ;   Beer is a float

maybe this helped some... thanks

[traumatic]

Yes, i,j and k stand for indexing variables.

Slightly OT but funny nevertheless:
http://mindprod.com/unmainnaming.html

[HeX0R]

*lol*

[freedimension]

i, j, k and l, m, n are used very often as index-variables when calculating with matrices. As every 2, 3 or n-dimensional array can be seen as a matrix, it's no wonder, those letters are used that often. Keep in mind, that many developers from the early days are mathematicians.

[griz]

I use x,y and t all the time. Does anyone else use t?

[Ralf]

I use x,y and t all the time. Does anyone else use t?

yes, but i use this only when operating with images (manipulate) and for arrays. Else i use something like lPosX, lPosY for example

[Rescator]

Another nice thing withh PureBasic is you can
use i.e x.l when using the variable in the code.
And if you do a mistake and type i.e x.w
the compiler will complain the type has allready been defined.
A nice way to avoid mistakes in critical code.

[Xombie]

I've been using iLoop and jLoop for god knows how long now. ^_^

[Tension]

@traumatic

Good link.

Also good to know I'm keeping to a standard.