Re: filter an array in place

[Drake Wilson <drake@...>]

Quoth Emmanuel Oga <emmanueloga@gmail.com>, on 2011-01-14 01:12:40 -0300:
> Is there any other more elegant way?

There's not much that's "elegant" in the sense of "easy using the Lua
table library" or such, that I can see.  If I were coding it all the
way down, I'd do something like this:

    function filtern(t, predicate)
       local j = 1
    
       for i, v in ipairs(t) do
          if predicate(v) then
             t[j] = v
             j = j + 1
          end
       end
    
       while t[j] ~= nil do
          t[j] = nil
          j = j + 1
       end
    
       return t
    end

So, copy all the desired values down in much the same way one would do
if filtering into a new table, then kill the rest of the contiguous
integer keys.  This relies on the fact that the filtering part never
generates more values than it consumes.

I don't much like the solutions involving table.remove or similar
because they result in O(N^2) table operations as opposed to O(N).

   ---> Drake Wilson