[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index] [Thread Index]

• Subject: Re: Issues with the current varargs implementation (Was: Re: inadequate documentation for select and table.unpack)
• From: "Soni L." <fakedme@...>
• Date: Tue, 21 Jun 2016 17:17:09 -0300

```

On 21/06/16 05:15 PM, Patrick Donnelly wrote:
```
```On Tue, Jun 21, 2016 at 3:59 PM, Sean Conner <sean@conman.org> wrote:
```
```It was thus said that the Great Patrick Donnelly once stated:
```
```On Tue, Jun 21, 2016 at 3:22 PM, Soni L. <fakedme@gmail.com> wrote:
```
```But varargs (and thus varargs-based arrays) are nil-safe by default.
```
```Show me in the manual where it says **tables** are not nil safe and
I'll stop posting to lua-l*.
```
```   Lua 5.3, section 3.4.7:

Unless a __len metamethod is given, the length of a table t is only
defined if the table is a sequence, that is, the set of its positive
numeric keys is equal to {1..n} for some non-negative integer n. In
that case, n is its length. Note that a table like

{10, 20, nil, 40}

is not a sequence, because it has the key 4 but does not have the
key 3.  (So, there is no n such that the set {1..n} is equal to the
set of positive numeric keys of that table.) Note, however, that
non-numeric keys do not interfere with whether a table is a
sequence.

But for this discussion:

function foo(...) print(select('#',...) end
function bar(t)   print(#t)             end

foo(1,2,3,4)
4
bar{1,2,3,4}
4
foo(nil,nil,3,nil)
4
bar{nil,nil,3,nil}
0
```
```There's an echo in this room. Apparently emphasizing **tables** is
lost on people so let me be crystal clear: table length is only
defined for sequences. __So__, while sequences are not nil-safe, that
does __not__ mean tables are not nil-safe.

```
```Thus, tables are not suitable as proper arrays.

--
Disclaimer: these emails may be made public at any given time, with or without reason. If you don't agree with this, DO NOT REPLY.

```

• Follow-Ups:
• References: