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

Alexey, could you expand on what you mean in your first point?

I guess that I meant two things here. First is that when I wrote a signature for my function, the compiler will make its best to help me implement it. It will yell at me, it will not let me use things that I am not supposed to use (according to constraints), etc. More precise I am with my types (e.g. use non-empty list instead of just list, use specific ADT instead of Bools, use Age/Weight/Size instead of Int, etc.) - more help I get. Another thing is that sometimes I'd just play "Type Tetris" to make things compile and work. Try something, the compiler says "No, can't have this", perhaps make a suggestion, try another thing, "aha, next step", etc. Learned so much from these "games" :) Regards, Alexey. On Thu, Jul 12, 2018 at 11:04 PM Brett Gilio wrote:

Alexey, could you expand on what you mean in your first point? I am quite intrigued. I do not use Haskell often, but that could be something of interest to me in-and-out of Haskell.

Brett Gilio brettg@posteo.net | bmg@member.fsf.org Free Software -- Free Society!

On 07/12/2018 07:46 AM, Alexey Raga wrote:

...

Not sure if it counts as "aha moments", but when I started with Haskell I had two major reasons (not in any importance order):

1. The ability to define the specification (types) and then "just" follow them in implementation. Sometimes even without having a clear understanding of the things I was using, I felt (and still feel) guided towards the right solution.

2. The ability to refactor fearlessly is a _massive_ productivity boost. Hard to underestimate.

Regards, Alexey.

On Wed, Jul 11, 2018 at 10:10 PM Simon Peyton Jones via Haskell-Cafe mailto:haskell-cafe@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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