[Haskell-cafe] What is your favourite Haskell "aha" moment?

[Jeffrey Brown]

"Blow your mind" on the Haskell Wiki[1] is a collection of short bits of
awesome code.

[1] https://wiki.haskell.org/Blow_your_mind

On Wed, Jul 11, 2018 at 2:40 PM Chris Smith <cdsmith at gmail.com> wrote:

> I feel like the one theme that's been missing in all of this is the
> interaction between equational reasoning and rewrite rules.  Examples of
> fusing operations on Text or ByteString were pretty impressive to me.  The
> ideas may be incorporated into other languages, but I believe Haskell
> is pretty unique, at least versus mainstream languages, in doing the fusion
> in the optimizer where there's still opportunity for the results to be
> inlined and further optimized.
>
> I don't have a complete example off the top of my head.
>
> On Wed, Jul 11, 2018 at 3:31 PM Scott Fleischman <
> scott.fleischman at plowtech.net> wrote:
>
>> We make extensive use of Servant for our web services at Plow
>> Technologies. It is my favorite example of the success of using types (even
>> relatively fancy types) to help with a common problem (creating web sites
>> with web services) and reduce boilerplate.
>>
>> I like the examples in the tutorial
>> <https://haskell-servant.readthedocs.io/en/stable/tutorial/index.html>.
>>
>> Scott Fleischman
>>
>>
>> On Wed, Jul 11, 2018 at 5:10 AM, Simon Peyton Jones via Haskell-Cafe <
>> haskell-cafe at haskell.org> wrote:
>>
>>> Friends
>>>
>>> In a few weeks I’m giving a talk to a bunch of genomics folk at the Sanger
>>> Institute <https://www.sanger.ac.uk/> about Haskell.   They do lots of
>>> programming, but they aren’t computer scientists.
>>>
>>> I can tell them plenty about Haskell, but I’m ill-equipped to answer the
>>> main question in their minds: *why should I even care about Haskell*?
>>> I’m too much of a biased witness.
>>>
>>> So I thought I’d ask you for help.  War stories perhaps – how using
>>> Haskell worked (or didn’t) for you.  But rather than talk generalities, I’d
>>> love to illustrate with copious examples of beautiful code.
>>>
>>>    - Can you identify a few lines of Haskell that best characterise
>>>    what you think makes Haskell distinctively worth caring about?   Something
>>>    that gave you an “aha” moment, or that feeling of joy when you truly make
>>>    sense of something for the first time.
>>>
>>> The challenge is, of course, that this audience will know no Haskell, so
>>> muttering about Cartesian Closed Categories isn’t going to do it for them.
>>> I need examples that I can present in 5 minutes, without needing a long
>>> setup.
>>>
>>> To take a very basic example, consider Quicksort using list
>>> comprehensions, compared with its equivalent in C.  It’s so short, so
>>> obviously right, whereas doing the right thing with in-place update in C
>>> notoriously prone to fencepost errors etc.  But it also makes much less
>>> good use of memory, and is likely to run slower.  I think I can do that in
>>> 5 minutes.
>>>
>>> Another thing that I think comes over easily is the ability to abstract:
>>> generalising sum and product to fold by abstracting out a functional
>>> argument; generalising at the type level by polymorphism, including
>>> polymorphism over higher-kinded type constructors.   Maybe 8 minutes.
>>>
>>> But you will have more and better ideas, and (crucially) ideas that are
>>> more credibly grounded in the day to day reality of writing programs that
>>> get work done.
>>>
>>> Pointers to your favourite blog posts would be another avenue.  (I love
>>> the Haskell Weekly News.)
>>>
>>> Finally, I know that some of you use Haskell specifically for genomics
>>> work, and maybe some of your insights would be particularly relevant for
>>> the Sanger audience.
>>>
>>> Thank you!  Perhaps your responses on this thread (if any) may be
>>> helpful to more than just me.
>>>
>>> Simon
>>>
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>>
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-- 
Jeff Brown | Jeffrey Benjamin Brown
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