Re: [PUZZLE] Appending to a list
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- Subject: Re: [PUZZLE] Appending to a list
- From: Andrew Starks <andrew@...>
- Date: Fri, 8 Sep 2017 12:51:12 -0500
On Fri, Sep 8, 2017 at 12:31 AM, Dirk Laurie <dirk.laurie@gmail.com> wrote:
> I used to have the following statement in nearly all of my programs.
>
> local append = tinsert
>
> where tinsert is a local variable with value table.insert. The idea is
> that when the `pos` parameter is omitted, I prefer for the sake of
> easy reading to use a different name.
>
> Today, I needed to do this instead:
>
> local append = function(tbl,x) tinsert(tbl,x) end
>
> Why would that be?
It's as Daurnimator said.
While it does nothing toHowever, I like:
local function append(tbl, x, ...)
if x == nil then
return tbl
else
tinsert(tbl, x)
return append(tbl, ...)
end
end
or the golf version...
local function append(tbl, x, ...)
return x == nil and tbl or append(tinsert(tbl, x) or tbl, ...)
end
Sorry. I saw puzzle and felt like participating. :)
>
> Once you have figured it out, the next question is: should I have
> expected table.insert to behave that way or is it a deviation from
> what the manual says?
>
I agree that optional middle parameters are extremely clever and
tricky and sometimes convenient.
- Andrew Starks