I can't understand the working of the generic for loop

[suloku]

I'm reading the lua programming manual, but I can't get how a generic loop works. I just want to know what exactly happens inside a loop like this:

    -- print all values of array `a'
    for i,v in ipairs(a) do print(v) end

Ok, tis prints all values of the array "a", but I don't get the sintax, maybe because of that "in" in there and the function ipairs(), which I don't know exactly what it does (and I couldn't find out).

Same for this example:

    -- print all keys of table `t'
    for k in pairs(t) do print(k) end

They say that this kind of for loops are powerful, but even if I can blindy use them and get the correct outputs, I want to know what happens in there and how to properly use them.

Thanks.

[H3xo]

I'm reading the lua programming manual, but I can't get how a generic loop works. I just want to know what exactly happens inside a loop like this:

    -- print all values of array `a'
    for i,v in ipairs(a) do print(v) end

Ok, tis prints all values of the array "a", but I don't get the sintax, maybe because of that "in" in there and the function ipairs(), which I don't know exactly what it does (and I couldn't find out).

Same for this example:

    -- print all keys of table `t'
    for k in pairs(t) do print(k) end

They say that this kind of for loops are powerful, but even if I can blindy use them and get the correct outputs, I want to know what happens in there and how to properly use them.

Thanks.

Code:

for Key,Value in pairs({"Key1" = 1, "Key2" = 2, "ThisIsAKey" = "ThisIsAValue"}) do
    print("Key: "..Key.." Value: "..Value)
end

Would print

Key: Key1 Value: 1
Key: Key2 Value: 2
Key: ThisIsAKey Value: ThisIsAValue

First argument is the key, second argument is the value.

Another example

Code:

local Table = {4,3,2,1}
for k,v in pairs(Table) do
    print(k.." "..v)
end

Would print

1 4
2 3
3 2
4 1

You can also do for,do loops like so

Code:

for i = 0, 24 do
    print(i)
end

That would output

1
2
3
4
5
6
7
..
..
24

Hope that helps

[suloku]

Thanks, now I understand it far better, I just need to look deeper in pairs() and ipairs() functions to fully understand that loops