WoW:API ipairs

Native Lua statement:

Used in loop constructs to iterate through the values of a table where the index are only numbers, or where there is no index (an array).

Example:

local fruits={"apple","orange","banana","kiwi"}

for index,value in ipairs(fruits) do 
  DEFAULT_CHAT_FRAME:AddMessage(tostring(index).." : "..value)
end

Result:

 1 : apple
 2 : orange
 3 : banana
 4 : kiwi

would be output to the chat window.

Note that ipairs() starts at index 1 and stops counting as soon as it reaches a nil value. Example:

> t = { [0]      = "zero",   --will not be counted
        [1]      = "one",    --will be counted; 1
        [2]      = "two",    --will be counted; 2
        [3]      = "three",  --will be counted; 3
        ["four"] = "four",   --will not be counted; returns 3
        [5]      = "five" }  --will never be reached
> for i,v in ipairs(t) do print(i..":"..v) end
1:one
2:two
3:three

Note that t[0] is never reached because it starts counting at [1], t["four"] is never reached because it is not an array index, and t[5] is never reached because the iterator ceases when it checks t[4] and finds a nil value.