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

[GrayFace <sergroj@...>]

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