On Wed, Mar 6, 2019 at 10:25 AM Tim Mackinnon <tim@testit.works> wrote:
> I still am tempted to make asDictionary work - because the the moment you
> get a #key , DNU error - which is definitely not right.
>
This argument gives me the willies. Sorry.
I can see an argument that a sequenceable collection can implement a
meaningful #asDictionary, using #keysAndValuesDo:. The key is the index of
each element, so it makes sense.
But, #asDictionary for a non-sequenceable collection doesn't make sense
(other than for Dictionary and its variants, obviously). What would the
keys be from a Set, for example?
Bag>>#asDictionary makes sense if (and in my opinion, only if) you define
it to rely on the internal implementation. #valuesAndCounts make sense
because it doesn't rely on internal implementation details to define it,
although it typically is implemented to use those internal implementation
details. I think expressing it as a conversion is a poor choice. Asking it
for a different representation is good.
[And as an aside, given that the API expresses #occurrencesOf:,
#valuesAndCounts might have been better named #valuesAndOccurrences (and
perhaps "With" rather than "And").]
> So should Bag asDictionary give you a reasonable dictionary, or should it
> throw a proper exception - something like:
>
> DomainError signal: ‘#asDictionary not supported, use #valueAndCounts’
>
> Is that better - or do we accept that it inherits it from Collection and
> so can do something useful?
>
> Tim
>
> On 6 Mar 2019, at 18:11, p...@highoctane.be wrote:
>
> And when asking the object:
>
> #(1 2 4 5 6 7 2 1 4 3) asBag isDictionary
>
> we get false. So, not, not a dictionary.
>
> I still have been using #valuesAndCounts to get the dictionary out of a
> bag on several occasions.
>
> And is useful indeed.
>
> #(1 2 4 5 6 7 2 1 4 3) asBag occurrencesOf: 2
>
> and
>
> #(1 2 4 5 6 7 2 1 4 3) asBag valuesAndCounts at: 2
>
> seem pretty much the same.
>
> But in this age of streams/reactive streams and lazy evaluations, what do
> we have in Pharo on that front?
>
> Phil
>
>
>
>
>
> On Wed, Mar 6, 2019 at 4:49 PM Sven Van Caekenberghe <s...@stfx.eu> wrote:
>
>> I was just explaining how it is now, what I think the rationale is behind
>> it.
>>
>> I understand #asDictionary as working on a collection of
>> pairs/associations (because it basically goes to #withAll:).
>>
>> A bag is just a collection that is optimised for many duplicates, the
>> fact that you have values and counts is more an implementation detail than
>> an intrinsic property.
>>
>> The conversion that you want, and that already exists in #valuesAndCounts
>> is one interpretation of what a bag is, not the only one. A bag is foremost
>> a collection of things.
>>
>> I am not immediately convinced that #valuesAndCounts should be the
>> default #asDictionary interpretation.
>>
>> What about the inverse for example ?
>>
>> { #foo->2. #bar->3 } asDictionary asBag.
>>
>> But this is certainly an interesting discussion.
>>
>> > On 6 Mar 2019, at 16:23, Tim Mackinnon <tim@testit.works> wrote:
>> >
>> > As Richard said - as a bag is relationship between keys and
>> frequencies, I would expect it to be able to convert to a dictionary.
>> >
>> > It displays in an inspector just like a Dictionary - which is why I
>> figured I could convert to pass it back to the exercise that was written
>> with Dictionaries in mind.
>> >
>> > <PastedGraphic-3.png>
>> >
>> >
>> > The code to fix it is quite simple, but on these kinds of things - I
>> thought it worth checking before submitting a PR.
>> >
>> > Tim
>> >
>> >
>> >> On 6 Mar 2019, at 13:53, Sven Van Caekenberghe <s...@stfx.eu> wrote:
>> >>
>> >> Why would that work ? What would you expect the output to be ?
>> >>
>> >> Try:
>> >>
>> >> #(1 2 3) asDictionary
>> >>
>> >> it fails in exactly the same way. You need key/value pairs
>> (Associations).
>> >>
>> >> These do work
>> >>
>> >> Bag new add: #foo->100; asDictionary.
>> >>
>> >> Bag new addAll: 'ABABABAAAA'; valuesAndCounts.
>> >>
>> >>> On 6 Mar 2019, at 14:25, Tim Mackinnon <tim@testit.works> wrote:
>> >>>
>> >>> I was surprised to find that a Bag can’t convert to a dictionary -
>> e.g.
>> >>>
>> >>> Bag new
>> >>> addAll: 'aabbbbcddd’;
>> >>> asDictionary
>> >>>
>> >>> Gives an error - Dnu #key
>> >>>
>> >>>
>> >>> It looks to me like Bag is inheriting a bad version of
>> #associationsDo: and instead could simply forward it to #doWithOccurences:
>> instead?
>> >>>
>> >>> I know Bag is not used that much - but it comes up a lot in
>> programming exercises.
>> >>>
>> >>> Tim
>> >>
>> >>
>> >
>>
>>
>>
>>
>
