I made a custom for i,v pairs, is it good or bad?

Help and Feedback Code Review
#1

I made a challenge to myself to make a custom I,v pairs, just so I can improve in finding other ways on “how to script this” stuff, anyway here’s the code

local tabel = {"mystuff","mywalletlol"}

local temp = 1

repeat
local v = tabel[temp]
print(v) -- replace this with your logic here
temp += 1
until temp == #tabel
temp = 0 -- important if your gonna do another custom I,v thing
1 Like
#2

Hi!

It’s great that you’re experimenting with alternative methods! I wish you all the success with further learning.

The function you are using works fine with arrays, and can handle 'gaps' or nil values too. That behaviour could be partially compared with ipairs() instead of pairs(), since ipairs() respects order in arrays, is the fastest of all the functions that can be used for iteration, but stops with it reaches the first ‘gap’.

I think you accidentally left out temp += 1 line inside the repeat loop.

local tab = {"A","B","C","D"}

local i = 1
repeat
	local v = tab[i]
	print(v)
	i += 1
until i > #tab -- #tab == last element, hence > relational operator
i = 0

Although for-loops and intended functions are the best possible way to interate through a table, it seems worth mentioning some interesting aspects of using repeat loops like this for learning purposes.

  • The above code can handle nil values (gaps) as well as dictionaries
local mixed_table = {
	x = "A",
	y = "B",
	[1] = "C",
	[2] = "D"
}
-->> C D

  • In case a table contains a lot of elements, repeat-loop is going to exhaust allowed execution time. That could be solved by adding a task.wait() statement every now and then, for example every time 200 more elements have been iterated. That also depends on how demanding the rest of the logic applied to each element is. pairs() and other such functions won’t exhaust all allowed time, on the other hand.

  • for-loops are easier to write and easy to understand.

  • Let’s quickly compare run time:

(Note: this is just a short comparison test and does not represent anything completely definite, as results may vary. However, it can serve us to show that pairs() is a little bit faster.

Quick test 
local REPEATS = 10

local array = table.create(5000,100) -- 5000 elements with the value of 100

local start,finish1,finish2
local sum1,sum2 = 0,0
local average1,average2
local x = 0
local i = 1

for i=1,REPEATS do
	start = os.clock() -------------------------------------------------
	
	i = 1
	repeat
		x += array[i]
		i += 1
	until i > 5000 -- #tab == last element, hence > relational operator
	i = 1
	sum1 += os.clock()-start
	
	x = 0
	
	start = os.clock() -------------------------------------------------
	
	for _,v in pairs(array) do
		x += v
	end
	sum2 += os.clock()-start
end

average1 = sum1/REPEATS
average2 = sum2/REPEATS

print((average1>average2 and "pairs()" or "repeat").." was faster:")
print(
	math.round(math.max(average1,average2)*100/math.min(average1,average2))/100 ..
	" times (approximate average)"
)

image

The result isn’t a constant number and depends on a variety of minor factors.

Have a nice day!

6 Likes
#3

nice, also I figured out something
If you put a function that yields in that loop it will be very slow bc it will wait for the current function to finish until the function is done, so is there any way to run a function more than once as pairs and ipairs?

Also, yeah I forgot to add that lol , edited post

1 Like