[Zope] dtml-in sort by generic function

[Oleg Broytmann]

Hi!

   Thank you for stepping in!

On Tue, 13 Mar 2001, Dieter Maurer wrote:
>  > but a colleague of mine, Dennis Otkidach suggested more general approach -
>  > to make a patch that will allow to pass a generic function to sort(),
> A very good idea!
>
> However, you should note:
>
>   *  "dtml-in" does not sort single values, but tuples
>      ( sort_values, client), where "sort_values" is
>      either a single value or a list of values and
>      "client" is the current element.
>
>      Your sort function must handle this case

   I know it! From time to time I scan and rescan Zope sources just for
better understanding and finding of hidden treasures (there are many :).

>   *  "dtml-in" supports multiple sort keys.
>      I would expect to have a comparison function for
>      each sort key, with the global comparison function
>      a composition of that for the sort keys.
>
>      Thus, you can combine a locale sensitive sort with
>      (e.g.) a date sort.

   But of course. Or simulating SQL "ORDER BY date DESC, title ASC" :)

   But I do not see a way to do it in generic fashion. I can write a
specific comparison function for every specific case, but how I can combine
few comparison functions into one in a generic way? Imagine a have a string
comparison str_cmp, and date comparison date_cmp functions. Now I need to
pass to dtml-in a combined function. Should it be a Python Script that just
calls str_cmp and date_cmp in turn, something like

   result = str_cmp(s1[0], s2[0])
   if result: return result # if not equal - order by first key

   result = date_cmp(s1[1], s2[1]) # else order by second key
   return result

Oleg.
----
     Oleg Broytmann     http://www.zope.org/Members/phd/     phd@phd.pp.ru
           Programmers don't die, they just GOSUB without RETURN.