XStream I think is exactly about it 2014-06-08 22:46 GMT+04:00 Camille Teruel <camille.teruel@gmail.com>:
On 8 juin 2014, at 19:20, Garth Holland <steve9571952@hotmail.com> wrote:
The pipe operator appears in many languages (F#, Haskell, Elixir, Clojure (threading macro)). It's an elegant way of chaining method/function calls in the presence of additional parameters. The reddit example could be written using a pipe operator |>
#('apple' 'peach' 'banana') |> groupedBy: #size |> select: [:each | each size even] |> values |> collect: #asCommaString.
The pipe operator is implemented as one of the examples of LanguageBox, a tool that permits to scope language extensions (it's a part of Helvetia made by Lucas Renggli).
I once thought that the pipe operator could be useful. But now I notice that the main (if not the only) recurrent use case I found is chaining queries on collections. If you have another recurrent use case (that is not purely idiomatic :) ) please let me know.
So yes, using the pipe operator make the snippet more readable but still has much inefficient: at each step a new collection is created just to be trashed afterward. Here it's not a problem but not all collections only have 3 elements ;).
For me it's a sign that the collection libraries lack a simple abstraction: composable filters (that is, iterators) to make complex queries. We could have collections answering #query that would responds a QueryBuilder object that would understand common enumeration methods, for example:
#('apple' 'peach' 'banana') query groupedBy: #size; select: [:each | each size even]; values; collect: #asCommaString.
This would return a CollectFilter on a ValuesFilter on a SelectFilter on a GroupedByFilter on the input collection. The QueryBuilder could then answer a message like #endQuery to compute and return the values obtained by the lastly created filter (embedded in a collection that conforms to the input collection's #species). Since it's just a composition of filter objects over the input collection, no useless intermediate collection is created: better performances & less stress on the GC.
Of course this idea is acceptable only if they are no other use cases where the pipe operator is a must.
/Garth
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