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Re: [Caml-list] Infix function composition operator
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Date: -- (:)
From: Jon Harrop <jonathandeanharrop@g...>
Subject: RE: [Caml-list] Infix function composition operator
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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