Re: table library changes (was Re: table.new in 5.3?)

[Sean Conner <sean@...>]

It was thus said that the Great John Hind once stated:
> > Date: Sun, 24 Nov 2013 17:58:12 -0500
> > From: Sean Conner <sean@conman.org>
> > Subject: Re: table library changes (was Re: table.new in 5.3?)
> >
> >
> >   So, aside from a performance optimization, yes, it can all be done in
> > pure
> > Lua.  But I also don't follow your "encourages inefficient coding'
> > logic
> > here.
> 
> Having the existing single element table.remove and table.insert encourages users to write code like:
> 
> t = {}
> for i=1, 10000 do t[i] = i end
> for i=10, 100 do table.remove(t, i) end
> 
> which is about 1000,000 table writes.
> 
> An optimised algorithm looks something like this:
> 
> t = {}
> for i=1, 10000 do t[i] = i end
> for i=11, 9899 do t[i] = t[91+i] end
> for i=10000, 9900, -1 do t[i] = nil end
> 
> only about 10,000 table writes.
> 
> Clearly, the optimised algorithm could be written in C as a multi-value
> remove library function, and like any algorithm it will be a faster in C
> than in Lua. But I do not think it will be sufficiently faster to justify
> its place in a C library.

  I actually went to the trouble to measure the code and indeed, the
"optimized" version does indeed run faster (about 10x), *BUT* it does *NOT*
produce identical results.  

  I realize you were trying to prove a point here, but it might be made a
bit better if both code fragments actually did identical work.

  -spc