On 15/06/07, Klaus D. Witzel <klaus.witzel at cobss.com> wrote:
> On Fri, 15 Jun 2007 15:50:54 +0200, Bert Freudenberg wrote:
> > On Jun 15, 2007, at 14:45 , sig wrote:
> >
> >> actually i missing these operations for dictionaries.
> >> in current implementation if you diff/union on two dictionaries,
> >> you'll find out that associations play role as set elements, not keys.
> >>
> >> for dictionaries 'a difference: b' i get not exactly what i would
> >> expect.
> >
> > Dictionaries are like other collections - a collection of "elements"
> > (the values). The keys are only interesting for accessing - like indices
> > on Arrays.  #do: operates on the values. So does #select:, and
> > #difference:. You wouldn't expect #difference: on an Array to work on
> > its indices, would you?
>
> Good argument. And if some solves that by (aDict keys op: bDict keys) and
> aDict's values are completely different from bDict values, no cDict can
> hold the "correct" values unless cDict is empty under all circumstances ;-)
>
> /Klaus
In my work i must maintain same number of keys in one dictionary as in
other, while their values are totally different. So, when first
dictionary changed somehow, then later i need to sync keys with second
one, but not values, because they constructed by other means. And
thats where set operations on keys only is useful.