Re: Embedded 'nil' values - a suggestion
[
Date Prev][
Date Next][
Thread Prev][
Thread Next]
[
Date Index]
[
Thread Index]
- Subject: Re: Embedded 'nil' values - a suggestion
- From: Wim Couwenberg <w.couwenberg@...>
- Date: Wed, 8 Mar 2006 23:00:21 +0100
>> It is possible. See also recent posts about this on this list:
>>
>> http://lua-users.org/lists/lua-l/2006-02/msg00537.html
>>
>> Specifically the "select("#", ...)" construct.
> Why thank you! Odd, but workable.
As another fun example, define the following functions:
local unpack, select = unpack, select
function pack(...)
local v = {...}
local n = select("#", ...)
return function(f, from, to)
from = from == nil and 1 or
from < 0 and n + 1 + from or
from
to = to == nil and n or
to < 0 and n + 1 + to or
to
return f(v, from, to)
end
end
function upairs(v, from, to)
return function(v, i)
i = i and i + 1 or from
if i <= to then
return i, v[i]
end
end, v
end
Examples:
> p = pack("aap", "noot", nil)
> =p(unpack)
aap noot nil
> =p(unpack, 1, -2)
aap noot
> =p(unpack, -2)
noot nil
> for i, v in p(upairs) do print(i, v) end
1 aap
2 noot
3 nil
> for i, v in p(upairs, -2) do print(i, v) end
2 noot
3 nil
--
Wim