How For loops match up with Pairs? [closed]
I have read through how for loops work, and I understand it. But when I try to match up that knowledge with what people say about pairs, it doesn't make sense.
For example, the easiest explanation of pairs that I could somewhat understand that I found was this.
1 | a={"This","is","an","Example"} |
2 |
3 | for k,v in pairs(a) do |
4 |
5 | print(v) |
6 |
7 | end |
According to how For loops are supposed to work, k is the starting value and v is the ending value. But why does printing v print out this is an Example? V is the ending value, it can't/hasn't been defined as anything?
I am just really confused. Can someone explain to me in simple terms how this stuff matches up?
2 answers
There are two kinds of for loops:
¤ Enhanced for loops / foreach loops
¤ Numeric for loops
What you used was a foreach loop. Often times, k and v are used in foreach loops to represent key and value. If you don't know what a key and value looks like,
1 | local t = { name = "emite1000" } |
2 | -- where `t` is the table, `name` is the key, and `"emite1000"` is the value. |
To my knowledge, the pairs iterator will go through each key and value so you can work with each one, but a lot of times the key is disregarded because it is not needed (in which case, some people like to use _ rather than k to signify that it isn't important).
1 | for _, v in pairs(Players:GetPlayers()) do |
2 | v:Kick() -- in this example, only the value is used. |
3 | end |
With your example, the keys in table a are automatically numeric because you didn't explicitly set them. So essentially your table also looks like this:
1 | a={[1]="This", [2]="is", [3]="an", [4]="Example"} |
Which means, printing the key and value like so...
1 | for k, v in pairs(a) do |
2 | print(k, v) |
3 | end |
Would print:
1 | 1 This |
2 | 2 is |
3 | 3 an |
4 | 4 Example |
No, k and v do not stand for a starting and ending value.
for loops take on two separate forms.
The simple incrementing:
1 | for index = start, stop, stride do |
and the generic iterator:
1 | for values in expression do |
The in makes a complete difference.
The thing to the right of the in, (e.g., pairs(tab)) describes a way to repeatedly get a list of variables (the things to the left, the k, v).
What pairs does is give out all of the keys and values (at that key) in a table. This is what k and v stand for.
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