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.

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> /Garth
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