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

[Conal Elliott]

> The fact that you can define the IO monad in Haskell was quite a
revelation.

But it's *not* a fact. It's a lie. And one of the most devious sort, since
the source code appears to agree. The purported definition couldn't
possibly explain concurrency.

On Wed, Jul 11, 2018 at 7:21 AM, Vanessa McHale <vanessa.mchale at iohk.io>
wrote:

> I find it quite elegant! The fact that you can define the IO monad in
> Haskell was quite a revelation. And it's especially nice when paired with a
> demonstration of C FFI (where you might *need* to sequence side effects
> such as freeing a value after it has been read).
>
> newtype IO <http://hackage.haskell.org/package/ghc-prim-0.5.2.0/docs/src/GHC.Types.html#IO> a <http://hackage.haskell.org/package/ghc-prim-0.5.2.0/docs/src/GHC.Types.html#local-6989586621679009802> = IO <http://hackage.haskell.org/package/ghc-prim-0.5.2.0/docs/src/GHC.Types.html#IO> (State# <http://hackage.haskell.org/package/ghc-prim-0.5.2.0/docs/src/GHC.Prim.html#State%23> RealWorld <http://hackage.haskell.org/package/ghc-prim-0.5.2.0/docs/src/GHC.Prim.html#RealWorld> -> (# State# <http://hackage.haskell.org/package/ghc-prim-0.5.2.0/docs/src/GHC.Prim.html#State%23> RealWorld <http://hackage.haskell.org/package/ghc-prim-0.5.2.0/docs/src/GHC.Prim.html#RealWorld>, a <http://hackage.haskell.org/package/ghc-prim-0.5.2.0/docs/src/GHC.Types.html#local-6989586621679009802> #))
>
>
> On 07/11/2018 09:14 AM, Stefan Monnier wrote:
>
> In a few weeks I'm giving a talk to a bunch of genomics folk at the Sanger
> Institute<https://www.sanger.ac.uk/> <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.
>
> I don't much like the monad solution for side-effects, but if those guys
> might have some knowledge of the horror of concurrent programming with
> locks, the STM system would be a good candidate.
>
>
>         Stefan
>
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> --
>
>
>
> *Vanessa McHale*
> Functional Compiler Engineer | Chicago, IL
>
> Website: www.iohk.io <http://iohk.io>
> Twitter: @vamchale
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