Table functions in Lua 5.2 Reference Manual

[Jakob Voss <jakob.voss@...>]

Hi,

I think that mixed and sparse tables (tables with some numeric indices 
but not limited to a range 1 to n) are the most difficult issue of Lua 
and a source of constant confusion. Unfortunately the Reference Manual 
does only help if you very carefully read all of it. Could you please 
update section 6.5 (Table Manipulation) of the Lua 5.2 Reference Manual 
with some additional hints? The section reads:

> Most functions in the table library assume that the table represents
> an array or a list. For these functions, when we talk about the
> "length" of a table we mean the result of the length operator.

1. What are "most functions" out of six? You should better list them by 
name or say "all but ..."

2. Please add "(see §3.4.6)." at the end of the section.

3. It is still not clear how the table methods work if you override the 
length operator with a __len metamethod. As I read the definition, this:

t = {[1]="a",[3]="b",[5]="c"}
setmetatable(t,{ len = function() return 5 end })
print( table.concat(t,",") )

should print "a,nil,b,nil,c", but it prints only "a". I only propose to 
change this behaviour but it is not what is written in the reference 
manual. I have not checked the other table functions, but I know that 
the current 5.2 manual does not really help, if I happen to use the 
table functions with sparse tables.

4. Is There really need for table.pack? As far as I understand, this 
both are equivalent:

t = table.pack(...)
t = {...}; t.n = #t

To clarify, it would be helpful to give the equivalence in the manual.

Jakob

--
Jakob Voß <jakob.voss@gbv.de>, skype: nichtich
Verbundzentrale des GBV (VZG) / Common Library Network
Platz der Goettinger Sieben 1, 37073 Göttingen, Germany
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