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

[Chris Smith]

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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