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Date: -- (:)
From: Till Varoquaux <till@p...>
Subject: Re: [Caml-list] Infix function composition operator
Thank you jon; this was a very insightful answer. Brought me one of
those palm forehead moments:
Most novice programmers don't understand the value restriction and
having an infix function composition operator in your standard library
is like throwing them under the bus.
In general I find that this (value restriction) is a problem I often
hit when writing combinator libraries in ocaml.

On Wed, Nov 10, 2010 at 7:51 AM, Jon Harrop
<jonathandeanharrop@googlemail.com> wrote:
> A pipeline operator is usually preferred over function composition in impure languages like OCaml and F# due to the value restriction. For example, your example would be written in F# as:
>
>  x |> op1 |> op2 |> op3 |> op4 |> op5
>
> This style is very common in F#, particularly when dealing with collections.
>
> Cheers,
> Jon.
>
>> -----Original Message-----
>> From: caml-list-bounces@yquem.inria.fr [mailto:caml-list-
>> bounces@yquem.inria.fr] On Behalf Of mark@proof-technologies.com
>> Sent: 10 November 2010 07:00
>> To: yminsky@gmail.com; arlen@noblesamurai.com
>> Cc: caml-list@inria.fr
>> Subject: Re: [Caml-list] Infix function composition operator
>>
>> on 10/11/10 3:45 AM, yminsky@gmail.com wrote:
>>
>> > This is probably a minority opinion, but I have written and read
>> quite a
>> lot
>> > of OCaml code over the years, and I've seen surprisingly few
>> effective
>> uses
>> > of the composition operator.  Somehow, I usually find that code that
>> avoids
>> > it is simpler and easier to read.
>>
>> I agree that using a composition operator can make the code obtuse, and
>> so
>> should not be overused.  But it's incredibly useful for certain
>> situations:
>>
>> 1) If you are performing a long chain of composed operations, it avoids
>> nested bracketing piling up.
>>
>> For example:
>>       (op5 <<- op4 <<- op3 <<- op2 <<- op1) x
>> Instead of:
>>       op5 (op4 (op3 (op2 (op1 x))))
>>
>> This sort of thing happens quite a lot in certain applications, e.g. in
>> language processing, to get at subexpressions.
>>
>> 2) Creating an anonymous function to be passed as an argument, it
>> avoids
>> explicitly mentioning arguments of that function.
>>
>> This sort of thing can happen a lot in functional programming
>> generally.
>>
>> For example:
>>       List.map (op2 <<- op1) xs
>> Instead of:
>>       List.map (fun x -> op2 (op1 x)) xs
>>
>> Mark Adams
>>
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