AW: vararg asymmetry
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- Subject: AW: vararg asymmetry
- From: "Michael Flad" <MichaelFlad@...>
- Date: Sun, 4 Mar 2001 13:00:28 +0100
Hi,
may not be the fastest way, but a recursive unpack should
work?
function unpack( table, nextidx )
if nextidx == nil then
nextidx = 1
end
if table.n > 1 then
table.n = table.n - 1
return table[nextidx], unpack(table, nextidx + 1)
else
return table[nextidx]
end
end
Regards,
Michael Flad
> Von: owner-lua-l@tecgraf.puc-rio.br
> [mailto:owner-lua-l@tecgraf.puc-rio.br]Im Auftrag von John Belmonte
> Gesendet: Sonntag, 4. März 2001 11:57
> An: Multiple recipients of list
> Betreff: vararg asymmetry
> Usually with Lua programming we discover something new and
> think, "wow I
> didn't realize that could be done". But sometimes the
> opposite occurs...
>
> I want an interface for packing/unpacking binary data that
> works like this:
>
> data = pack(template, val1, val2, ..., valn)
> val1, val2, ... valn = unpack(template, data)
>
> However as far as I know there is no way to implement unpack
> in Lua because
> the output of a function (that is, the number of values)
> cannot be generated
> by program. (I do realize that I can just use tables. Also,
> I suppose it's
> possible to generate the required code on the fly and use
> dostring but that
> is not very reasonable.) On the other hand, the input of a
> function can be
> generated easily (by making a table and using call) so there
> seems to be a
> lack of symmetry in the standard library. What I'm trying to
> do with unpack
> is not so bizarre. In fact the function strfind in the
> standard library
> does the same thing, so it also could not be implemented in
> Lua. Maybe
> adding a function like this would be useful:
>
> expand (table)
>
> Return elements of table with indexes 1..getn(), in
> order, as individual
> values.
>
>
> -John