Re: Lua 5.4-work1 with first class arrays (implementation & benchmarks)

[Philipp Janda <siffiejoe@...>]

Am 28.03.2018 um 18:04 schröbte Petri Häkkinen:
> The differences with arrays emulated with tables are:
>
> + much, much higher performance than possible with ’n’ field trick
> + standardized way to query the length (using the # operator)
> + the length is automatically updated when you insert values — this is essentially for free

Couldn't you just add the length-updating code to normal tables? I mean 
we already pay the extra space for the length field. Then we wouldn't 
need a table subtype or new syntax, and the following code would 
continue to work as expected:

    function tcopy( t )
      local copy = {}
      for k,v in pairs( t ) do
        copy[ k ] = v
      end
      return copy  -- returns an array if given an array
    end

> Petri

Philipp


p.s. I believe this proposal isn't new and was rejected because of the 
extra space and performance cost for non-array tables, but maybe your 
benchmarks change that.