Hi simon, I feel a lot of aha in Haskell. However, the most basic characterise I think are the following. * Algebraic data type (*Extremely wonderful*) * Pattern matches * Higher-order function * Partial application * Polymorphic type * Recursion and Lazy pattern I show its features in the code below. Simple code example 1: ```Haskell -- Algebraic data type data DNA = A | C | G | T deriving Show -- Using algebraic data type with list dna1 :: [DNA] dna1 = [A,A,T,C,C,G,C,T,A,G] -- Pattern matches abbrev :: DNA -> String abbrev A = "adenine" abbrev C = "cytosine" abbrev G = "guanine" abbrev T = "thymine" -- Higher-order function and Partial application abbrevDNAs = map abbrev -- Interactive example {- ghci> abbrevDNAs [A,A,C,G,A,T] ["adenine","adenine","cytosine","guanine","adenine","thymine"] -} ``` Simple code example 2: ```Haskell -- Algebraic data type data RNA = A | C | G | U deriving Show data Amino = Ala | Arg | Asn | Asp | Cys | Gln | Glu | Gly | His | Ile | Leu | Lys | Met | Phe | Pro | Ser | Thr | Trp | Tyr | Val | Error deriving Show -- Pattern matches rna2amino :: [RNA] -> Amino rna2amino [A,A,A] = Lys rna2amino [A,A,G] = Lys rna2amino [G,A,A] = Glu rna2amino [A,U,G] = Met rna2amino [C,A,U] = His rna2amino _ = Error -- Higher-order function convert :: [RNA] -> [Amino] convert xss = map rna2amino $ splitN 3 xss -- Polymorphic type, Recursion and Lazy pattern splitN :: Int -> [a] -> [[a]] splitN _ [] = [] splitN n xs = let (as,bs) = splitAt n xs in as : splitN n bs -- Interactive example {- ghci> convert [A,A,A,G,A,A,A,U,G,C,A,U] [Lys,Glu,Met,His] -} ``` Of course, I am not familiar with genom :) Regards, Takenobu 2018-07-11 21:10 GMT+09:00 Simon Peyton Jones via Haskell-Cafe < haskell-cafe@haskell.org>:
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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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