Re: LPeg 0.10

[HyperHacker <hyperhacker@...>]

On Tue, Nov 9, 2010 at 19:57, Norbert Kiesel <nkiesel@tbdnetworks.com> wrote:
> On Wed, 2010-11-10 at 11:36 +0900, Miles Bader wrote:
>> Nick Gammon <nick@gammon.com.au> writes:
>>
>> >> * Changes from version 0.9 to 0.10
>> >
>> > If I may just point out, doing either a string or numeric comparison,
>> > version 0.10 is a lower version than 0.9.
>> >
>> > print ("0.10" > "0.9") --> false
>> > print (0.10 > 0.9)  --> false
>>
>> Nonetheless, it's a very standard format for version numbers.
>>
>> When comparing version strings, you should compare runs of digits in
>> isolation, as numbers.  Most package-handling programs should do that
>> automatically (and glibc even contains a variant of strcmp that does it
>> -- "strverscmp").
>>
>> -Miles
>>
>
> Something like this
>
> function strverscmp(a, b)
>   if type(a) == 'string' and type(b) == 'string' then
>      local aa = a:gmatch('%d+')
>      local bb = b:gmatch('%d+')
>      while true do
> local na = aa()
> local nb = bb()
> if not na and not nb then return 0 end
> if not na then return -1 end
> if not nb then return 1 end
> local delta = tonumber(na) - tonumber(nb)
> if delta < 0 then return -1 end
> if delta > 0 then return 1 end
>      end
>   elseif type(a) == 'number' and type(b) == 'number' then
>      return a - b
>   end
>   return nil
> end
>
> function test(a, b)
>   print(a, b, strverscmp(a, b))
> end
>
> test('0.9', '0.10')
> test('0.9', '0.9')
> test('0.9.1', '0.10')
> test('0.9.1', '0.9.0')
> test('0.9.1', '0.9.2')
> test(0.9, 0.9)
>
> </nk>
>
>
>
>

Just for what it's worth, assert() is better for testing:
assert(strverscmp('0.9', '0.10') < 0)
(Also it's for this reason I like to use a datecode for my version
numbers. 20 (or more) bits: yyyyyyymmmmdddddiiii (i=index).)

-- 
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