Re: Request for 5.4: adding [] as table creation syntax for Lua 6.0

["Soni L." <fakedme@...>]

On 14/07/16 09:22 AM, Egor Skriptunoff wrote:
> On Thu, Jul 14, 2016 at 2:01 PM, Philipp Janda <siffiejoe@gmx.net 
> <mailto:siffiejoe@gmx.net>> wrote:
>
>     Am 14.07.2016 um 10:13 schröbte Egor Skriptunoff:
>
>         On Thu, Jul 14, 2016 at 11:01 AM, Daurnimator
>         <quae@daurnimator.com <mailto:quae@daurnimator.com>> wrote:
>
>
>                 Maybe, {1, 2, 3} for tables, @{1, 2, 3} for arrays
>                 (with array metatable
>                 applied)?
>
>
>             In that case, why not use the already valid: S(1,2,3)
>
>         Three reasons:
>         1) Standardization of array type in Lua (all the developers
>         will use the
>         same implementation of arrays)
>         2) Avoidance of performance penalty due to passing vararg to a
>         function
>
>
>     What performance penalty? 
>
>
> Lua pushes all the arguments to the stack to invoke S(1,2,3),
> and inside S() Lua pushes them AGAIN for constructing a table.
> "VARARG" bytecode is not O(1) instruction, it was discussed earlier in 
> this list.

That's only true for PUC Lua. That is,

local function array(...)
  local function arrayco(...)
    while true do coroutine.yield(...) end
  end
  local co = coroutine.wrap(arrayco)
  co(...)
  return co
end

is usable in sane Lua implementations. Stop using the PUC Lua 
interpreter and you won't have any more complaints about this stuff.

> Moreover, S(1,2,3) does not work for arrays longer than 256 elements.
>
>     `f@{ 1, 2, 3 }` isn't that much better, though ...
>
> Quite nice with a space between :-)
> func @{1,2,3}

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