[joeyo]

It's certainly sane in the sense that it was an intentional, if perhaps unusual, design decision. I personally like it since it results in an efficient implementation of sparse arrays.

In any event, Lua 5.2 will respect the __len, __pairs and __ipairs metamethods, so you can tweak this behavior if you need to store nils in your tables and iterate over them.

[stdbrouw]

The world would be a beautiful place if everything intentional were sane :-) It's bitten me a couple of times (e.g. when unpacking arguments in a function to feed them to another function, where one of the arguments is nil) but I can see how it could be the desired behavior in some cases.