[Haskell-cafe] Standard package file format

Harendra Kumar harendra.kumar at gmail.com
Sat Sep 17 02:35:38 UTC 2016

Since I triggered this discussion I feel obligated to summarize the
important points that were presented. Is there a good place to record
Haskell ecosystem related discussions (some wiki)?


On 17 September 2016 at 05:57, Paolo Giarrusso <p.giarrusso at gmail.com>

> On Friday, September 16, 2016 at 3:42:48 PM UTC+2, Kosyrev Serge wrote:
>> Chris Kahn writes:
>> > I would like to second this thought. Using Haskell for package
>> > descriptions needs to be thought out and executed with great care and
>> > attention. It's really easy to go off the rails.
>> >
>> > Scala's build system lets you do very powerful things, but it also
>> > makes things unnecessarily complicated and mystifying for beginners.
>> > At my previous work where we used Scala extensively, there were many
>> > times where the team simply resorted to external tools because
>> > figuring out how to make some seemingly trivial change to an SBT
>> > module was too time consuming.
>> Let me guess (have no idea about sbt) -- unbridled Turing completeness?
>> Declarativity is king for configuration, and Turing completeness ain't it
>> --
>> please, see my other mail about subsetting Haskell.
> That's not the main problem with SBT. How do I explain it? Take this as an
> example of what Haskell should *not* do.
> # SBT made difficult
> Look, we all know a monad is just a monoid in the category of
> endofunctors, right?. Now, a SBT build configuration is just a
> heterogeneously-typed map from keys to monadic values that can be evaluated
> to a graph of setting transformers and build actions, so what's the problem?
> And oh, I forgot to mention keys aren't simple strings but have a
> hierarchy themselves, and this hierarchy is used for inheritance and
> overriding of settings (nothing as simple as OO inheritance, mind you,
> think of something like CSS but different).
> Isn't using Haskell supposed to require a PhD? So why would its build
> tools use something so simple as nested records, like Cabal does?
> </sarcasm>
> I think I'm trolling, but the above is somewhat accurate (except for any
> misunderstanding of SBT I might have)—I personally enjoy using SBT and its
> power, and once you learn it can be reasonably easy, but I think Kmett's
> lens library might be simpler to learn.
> In fairness, many SBT builds can be read without having any clue of the
> above, because they look like imperative programs. But as soon as you need
> to do a bit more or you make a type error, you end up facing some of the
> above complexity—if you want, the "imperative program" abstraction is
> extremely leaky.
> For instance, here's something "easy" (but count the amount of custom
> symbolic operators):
> scalaVersion := "2.11.0"
> scalacOptions += "-deprecation"
> libraryDependencies += org.scalatest" %% "scalatest" % "2.0"
> Then you want to use one setting when defining another, and suddenly you
> end up with:
> libraryDependencies <+= scalaVersion (ver => "org.scala-lang" %
> "scala-compiler" % ver)
> Luckily, this can be done more easily nowadays, thanks to Scala macros O_O.
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