Lua doesn't like you, or, a table is not always a table

In Lua, everything is a table, and everything that isn’t a table is just syntax sugar around a table.

Tables are often - when they have only successive integer indices - internally implemented using arrays.

So iterating over them will iterate in key order.

But don’t be fooled that this will always be true.

Observe:

~ % lua                                                                                                                      ~
Lua 5.3.4  Copyright (C) 1994-2017 Lua.org, PUC-Rio
> t={}
> t[1]="foo"; t[2]="bar"; t[3]="baz"
> i,v = next(t,nil)
> while i do
>> print(i,v)
>> i,v=next(t,i)
>> end
1	foo
2	bar
3	baz
> t[1]=nil
> t[8]="foo"
> i,v = next(t,nil)
> while i do
print(i,v)
i,v=next(t,i)
end
8	foo
2	bar
3	baz
> 

As long as you have a table that looks like an array - which lua also has syntax sugar for creating:

> t = {"foo","bar","baz"}
> t[1]
foo
> t[3]
baz

- iterating it (next is the “primitive” for iteration in lua) will behave nice and iterate in key order.

If your table doesn’t… well, it’ll be hash order. Good luck.