Re: Cant think of an elegant lua solution to this little problem

[Paul K <paulclinger@...>]

Hi Sergey,

> This won't work in case of "a012" vs "a12". It will think the strings are
> identical, but they're not. Windows places "a012" first. It's easy to fix by
> simply returning s1 < s2 in case padded strings are the same. The limitation

I'm not sure if this is by coincidence or not (as it may be just
treated as the same value, which means that the sort order will be
arbitrarily picked between 012 and 12), but it should be easy to fix
the logic if you want a specific order; just add the length:

function alphanumsort(o)
  local function padnum(d) return
("%012d"):format(d)..("%02d"):format(12-#d) end
  table.sort(o, function(a,b)
    return tostring(a):gsub("%d+",padnum) < tostring(b):gsub("%d+",padnum) end)
  return o
end

Use format(12-#d) if you want 012 before 12 or format(#d) if you want
12 before 012 (this is assuming the length is 12 or less). I'll update
the blog post to reflect this.

Paul.

On Sat, Aug 25, 2012 at 7:52 AM, GrayFace <sergroj@mail.ru> wrote:
> On 25.08.2012 6:03, Ignacio Burgueño wrote:
>>
>> Something like natural sort may suit you, perhaps?
>>
>>
>> http://notebook.kulchenko.com/algorithms/alphanumeric-natural-sorting-for-humans-in-lua
>
>
> This won't work in case of "a012" vs "a12". It will think the strings are
> identical, but they're not. Windows places "a012" first. It's easy to fix by
> simply returning s1 < s2 in case padded strings are the same. The limitation
> of 12 digits is a harder one.
>
> Here's an implementation I've just made, I really like it:
> -- return s1 < s2, but with natural comparison of numbers:"2" < "12"
> function alnumcmp(s1, s2)  -- return s1 < s2
>     if s1 == s2 then  return false  end
>     local n1, n2 = 1, 1
>     repeat
>         local i1, i2, c1, c2
>         i1, c1, n1 = s1:match("0*(%d*)([^%d]*)()", n1)
>         i2, c2, n2 = s2:match("0*(%d*)([^%d]*)()", n2)
>         if #i1 ~= #i2 then  return #i1 < #i2  end
>         if i1 ~= i2 then  return i1 < i2  end
>         if c1 ~= c2 then  return (n1 > #s1 and c1 or c1.."0") < (n2 > #s2
> and c2 or c2.."0")  end
>     until n1 > #s1 and n2 > #s2
>     return s1 < s2
> end
>
> --
> Best regards,
> Sergey Rozhenko                 mailto:sergroj@mail.ru
>
>