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On 04/01/17 12:06 PM, Gary V. Vaughan wrote:
On Jan 4, 2017, at 4:32 AM, Soni L. <> wrote:

On 04/01/17 02:24 AM, 聂威 wrote:
dear list,

I have noticed that `table.unpack(list [,i [, j]])` will NOT regards the `n` field in the `list` table,

I know I can write it like this:

table.unpack(list, 1, list.n)

but will it be a good idea to make it read `n` field in table.unpack?

thanks and happy new year!


table.pack in Lua 5.3 manual:


      |table.pack (···)|

Returns a new table with all parameters stored into keys 1, 2, etc. and with a field "|n|" with the total number of parameters. Note that the resulting table may not be a sequence.

Here's a better idea:

Why not make table.pack return a table, the value 1, and the total number of parameters?

That way, table.unpack(table.pack(f())) is equivalent to f().
But why? There is no practical reason to immediately unpack what was just packed. At some point you need to access the packed values.


    local args, from, to = table.pack(...)
    -- or argsvalues = table.pack(table.pack(...))?
    -- or argstable = {table.pack(...)}?
    local r = {n=from}
    for i = from, to do
      r[i] = process(args[i])

versus, IMHO clearer:

    local args = table.pack(...)
    local r = {n=args.n}
    for i = 1, args.n do
       r[i] = args[i]


t, 1, n is more useful than t, t.n for functions that take a table, a start and an end.

process(table.pack(...)) vs local t = table.pack(...) process(t, 1, t.n)

Would also be nicer if the standard table library were object-oriented:

table.sorter(function(a, b) return b < a end)(table.pack(...)) -- auto-sort args
table.concater(" | ")(table.pack(...)) -- auto-concat args
io.write(table.concater("\t")(processtostring(table.pack(...))),"\n") -- print(...) implementation, where processtostring calls tostring on every element

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