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Option functions (or lack thereof) + operator for composition
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Date: -- (:)
From: bluestorm <bluestorm.dylc@g...>
Subject: Re: [Caml-list] Option functions (or lack thereof) + operator for composition
On Tue, Nov 16, 2010 at 3:26 PM, Michael Ekstrand <michael@elehack.net>wrote:
>
> Batteries provides operators for things like this.  It defines the '**>'
> operator for function application; it's an odd name, but it has the
> right associativity.  As Dmitry mentioned, some override (&).  Batteries
> also provides composition operators |- and -|, and a pipeline operator
> |> (opposite of **>).  With that operator, you can write:
>
>    f x y |> ignore
>
> thereby putting the emphasis on "f x y" and relegating "ignore" to a
> cleanup at the end.
>
> - Michael


(<|) as inverse of (|>) is also available. It doesn't have the "right"
associativity, but you can easily use (f -| g -| h <| x) instead of (f **> g
**> h **> x).

Though I find the application-as-pipeline style quite readable in some
cases, I think that in general it is more often superfluous than not.
Besides, as mentioned recently on this list, overuse of the function
composition operators (|-) and (-|) are also call for troubles with the
value restriction.
All in all, I think it's reasonable to stay conservative and not advertise
funky binary operators too loudly.

That said, domain-specific binary operators are certainly useful for
readability in some contexts --- that's what an infix operator is anyway :
an unreadable-by-design symbol that only get meaning by domain-specific
conventions. Local open in, available by standard since OCaml 3.12, allow us
to neatly encapsulate such domain-specific notations into OCaml modules.