Re: Definition of table.insert

[Henning Diedrich <hd2010@...>]

Hi Alex,

On 1/8/11 12:00 PM, Alexander Gladysh wrote:

You can not be sure what user meant by this. Perhaps he does want to insert nil.

Note that even when this behavior is expected, this code is not
necessary bugged:

insert(t,n,somefunction(...))
insert(t,n,somefunction(...))
insert(t,n,somefunction(...))

It's about the n:

if you say 'not necessarily buggy' that is hedged enough to be true.

 But already your 3 line snip can lead to insert() making replacements instead of pushing existing values up.

You could for only /one/ nil, /still/ end up with a table only holding 1 value, not 2.

If you have these n:

insert(t,1,somefunction(...))
insert(t,2,somefunction(...))
insert(t,2,somefunction(...)) -- 2 again!

Intuitively, of course, the last line is expected to always push the forelast's value up.

But instead, it /deletes/ and overwrites that forelast value, if somefunction(...) returned nil in the /first/ line.

That's pretty nasty in my eyes. Your second line's value is gone by virtue of the combination of the first and second. Only 'inserts' in play:

insert(t,1,nil)
insert(t,2,'a')
insert(t,2,'b') -- 2 again!

-- table is now { 2:'b' }

Henning