From brad73435 at gmail.com  Tue Sep 12 00:45:43 2023
From: brad73435 at gmail.com (Brad Smith)
Date: Mon, 11 Sep 2023 17:45:43 -0700
Subject: [Haskell-beginners] Beginner question.
Message-ID: <CACFAuZ84_RJZ_aC1dNdbixzxuFg4Xm83N5G6GqtPukweM_m+Jg@mail.gmail.com>

I just started working my way through a Haskell book... first time with
functional programming. Mid way through the first chapter she's
introducing point-free programming with a trivial example transitioning
from not point-free...

makeGreeting salutation person = salutation <> " " <> person

to point free...

makeGreeting' = (<>) . (<> " ")

After a little playing with it... it seems to make sense. So I thought I'd
try evolving from salutation and name to salutation, first, and last names.
But, after a bit of tinkering, I haven't been able to make it work...

I'm sure it's something simple (one way or the other)... any help would be
appreciated!

Brad
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From sylvain at haskus.fr  Tue Sep 12 08:07:42 2023
From: sylvain at haskus.fr (Sylvain Henry)
Date: Tue, 12 Sep 2023 10:07:42 +0200
Subject: [Haskell-beginners] Beginner question.
In-Reply-To: <CACFAuZ84_RJZ_aC1dNdbixzxuFg4Xm83N5G6GqtPukweM_m+Jg@mail.gmail.com>
References: <CACFAuZ84_RJZ_aC1dNdbixzxuFg4Xm83N5G6GqtPukweM_m+Jg@mail.gmail.com>
Message-ID: <a601f7ba-e435-cb4b-ad17-c5f2740b9e7e@haskus.fr>

Hi,

https://pointfree.io/ gives:

Input: f x y z = x <> " " <> y <> " " <> z

Output: f = ((<>) .) . flip flip " " . ((<>) .) . (<>) . (<> " ")

So no, it's not something simple!

For clarity I would recommend using the non-point-free version, even in 
the case given in the book. Use point-free only in simple cases like 
`map (+ 1)` where the meaning is obvious.

Sylvain


On 12/09/2023 02:45, Brad Smith wrote:
> I just started working my way through a Haskell book... first time 
> with functional programming. Mid way through the first chapter she's 
> introducing point-free programming with a trivial example 
> transitioning from not point-free...
>
> makeGreeting salutation person = salutation <> " " <> person
>
> to point free...
>
> makeGreeting' = (<>) . (<> " ")
>
> After a little playing with it... it seems to make sense. So I thought 
> I'd try evolving from salutation and name to salutation, first, and 
> last names. But, after a bit of tinkering, I haven't been able to make 
> it work...
>
> I'm sure it's something simple (one way or the other)... any help 
> would be appreciated!
>
> Brad
>
> _______________________________________________
> Beginners mailing list
> Beginners at haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners

From brad73435 at gmail.com  Tue Sep 12 13:35:14 2023
From: brad73435 at gmail.com (brad73435 Smith)
Date: Tue, 12 Sep 2023 06:35:14 -0700
Subject: [Haskell-beginners] Beginner question.
In-Reply-To: <a601f7ba-e435-cb4b-ad17-c5f2740b9e7e@haskus.fr>
References: <a601f7ba-e435-cb4b-ad17-c5f2740b9e7e@haskus.fr>
Message-ID: <8E4007FD-FB45-43D8-9AA9-324F6C4C2CF1@gmail.com>

That’s an impressive step in complexity!

FWIW, for ‘f x y = x <> " " <> y’ that website gave the same result as the book… ‘f = (<>) . (<> " ")’… so it seems to do a good job of giving a simplified solution. 

Understood re only using point-free for simple, clear cases… though it was a good exercise for me to understand what’s going on with the function composition operator (.).

Thank you!
Brad

Sent from my iPhone

> On Sep 12, 2023, at 1:08 AM, Sylvain Henry <sylvain at haskus.fr> wrote:
> 
> Hi,
> 
> https://pointfree.io/ gives:
> 
> Input: f x y z = x <> " " <> y <> " " <> z
> 
> Output: f = ((<>) .) . flip flip " " . ((<>) .) . (<>) . (<> " ")
> 
> So no, it's not something simple!
> 
> For clarity I would recommend using the non-point-free version, even in the case given in the book. Use point-free only in simple cases like `map (+ 1)` where the meaning is obvious.
> 
> Sylvain
> 
> 
>> On 12/09/2023 02:45, Brad Smith wrote:
>> I just started working my way through a Haskell book... first time with functional programming. Mid way through the first chapter she's introducing point-free programming with a trivial example transitioning from not point-free...
>> 
>> makeGreeting salutation person = salutation <> " " <> person
>> 
>> to point free...
>> 
>> makeGreeting' = (<>) . (<> " ")
>> 
>> After a little playing with it... it seems to make sense. So I thought I'd try evolving from salutation and name to salutation, first, and last names. But, after a bit of tinkering, I haven't been able to make it work...
>> 
>> I'm sure it's something simple (one way or the other)... any help would be appreciated!
>> 
>> Brad
>> 
>> _______________________________________________
>> Beginners mailing list
>> Beginners at haskell.org
>> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
> _______________________________________________
> Beginners mailing list
> Beginners at haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners