2016-04-20 14:46 GMT+03:00 Bram Moolenaar <[email protected]>:
>
> Björn Linse wrote:
>
>> > The NULL is supposed to be the same as an empty, mutable list. This is
>> > tricky, because code that expects a list needs to check for the NULL and
>> > create the list if needed.
>>
>> how could this be possible?
>>
>> let x = getreg("a",1,1) " returns NULL
>> let y = x
>> call add(x, "text")
>>
>> now x is created, but y is still NULL, inconsistent with if x referred
>> to an non-NULL empty list.
>
> OK, yes, in that case it is different from a real empty list.
> Do we really case about that?
Do you really want to state in documentation “lists are passed by
reference, but *some* empty lists are passed by value”? If I got
mutable empty list from somewhere I expect it to work as mutable empty
list. E.g. I could use
function Extender(lines)
call extend(a:lines, systemlist('echo abc'))
endfunction
. Now pass v:_null_list to Extender: what will it do? `a:lines` is a
new variable, destroyed after function exits.
>
> --
> Nothing is impossible for the man who doesn't have to do it.
>
> /// Bram Moolenaar -- [email protected] -- http://www.Moolenaar.net \\\
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