Re: A review of changes between 5.1 and 5.2-work3

[Duncan Cross <duncan.cross@...>]

On Thu, May 20, 2010 at 4:38 PM, Peter Cawley <lua@corsix.org> wrote:
> To help understand all of the changes between Lua 5.1(.4) and Lua
> 5.2-work3, I took I diff of the source folders of the two, then
> distilled the resulting 16000 line diff line into an easier to read
> blog post. You may be interested in reading the result (and feedback
> is also welcomed):
>
> http://www.corsix.org/content/look-lua-52-work3
>

Very neat - thanks!

 "Note that even with deprecation of ipairs disabled, the behaviour of
  ipairs differs in 5.2-work3 from that of 5.1; specifically, it
  respects the length operator (...)"

As Roberto pointed out [1], it only refers to the length operator when
it's on a nil value, so in certain (probably unlikely) circumstances
it actually won't fully respect the length operator:

 > a = setmetatable({}, {__len = function()  return 3;  end})
 > for i,v in ipairs(a) do  print(i,v);  end
 1       nil
 2       nil
 3       nil
 > a[4] = true
 > for i,v in ipairs(a) do  print(i,v);  end
 1       nil
 2       nil
 3       nil
 4       true


[1] http://lua-users.org/lists/lua-l/2010-05/msg00342.html

-Duncan