Hi,
indeed, transducers provided a way to achieve this, e.g.
#(12 7 'a' nil #(0)) pipe
filter: #notNil;
filter: #isNumber;
map: #squared;
filter: #even;
into: OrderedCollection.
But this feature is deprecated, as it was not that useful. The preferred
way to do this is either:
#(12 7 'a' nil #(0))
transduce: #notNil filter * #isNumber filter * squared map * #even filter
reduce: Set accumulate.
or:
Set <~ #even filter
<~ #squared map
<~ #isNumber filter
<~ #notNil filter
<~ #(12 7 'a' nil #(0)).
The advantage of the transducer approach is that it decouples
filtering/mapping/etc. from iteration and aggregation. This facilitates
reuse and makes it trivial to provide all operations to new custom data
types.
However, I didn't have time to finish the Pharo port of Transducers, yet.
Hence, the a current version is available in Cincom's Public Store or
(most current) directly from me only. But if you are interested and have a
nice use case, I'd be happy to help out.
Best, Steffen
Am .10.2018, 08:45 Uhr, schrieb Julien <
[hidden email]>:
> I think this was the idea of Transducers as well.
>
> Julien
>
> ---
> Julien Delplanque
> Doctorant à l’Université de Lille
>
http://juliendelplanque.be/phd.html> Equipe Rmod, Inria
> Bâtiment B 40, Avenue Halley 59650 Villeneuve d'Ascq
> Numéro de téléphone: +333 59 35 86 40
>
>> Le 17 oct. 2018 à 09:13, Peter Uhnak <
[hidden email]> a écrit :
>>
>> Hi,
>>
>> is there some library that will allow me to chain select:/collect:/...
>> via cascade?
>>
>> E.g.
>>
>> #(12 7 'a' nil #(0)) query reject: #isNil; select: #isNumber; collect:
>> #squared; select: #even?
>>
>> The point is to not have to write billion parentheses when building a
>> more complex query.
>>
>> I imagine this would be pretty easy to write, but figured I ask first.
>>
>> Thanks,
>> Peter
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