On 3/26/21 7:08 PM, Marcel Taeumel wrote:
> What do you think? Does it makes sense to pursue this idea of 
> "dictionaries with collections as values" and enrich it with tests and 
> documentation?

I frequently use dictionaries mapping keys to sets of values. I rely 
often on these invariants:

  - retrieval of a not-present key yields an empty collection

  - removal of all the items from a given key's collection automatically
    removes the key as well

I've never needed 'size' to yield anything other than the number of keys.

Christoph's concerns about interface/implementation explosion are 
well-founded, though, I reckon; do... do we still have traits in Squeak?

Cheers,
   Tony