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Why isn't Haskell popular in industry?

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Re: Why isn't Haskell popular in industry?

#51

Post by tkahn6 »

barrkel wrote: post #39
silentbicycle wrote: post #18

Earlier quoted context omitted.

Because it has typeclasses, which solve the same problems without creating the new problems that conventional objects do. Why doesn't Java support pattern matching?

Typeclasses don't solve the same problems as objects do. Typeclasses are a way of getting access to more operations in polymorphic code, which in functional languages is a compile time feature; they're also a way to implement overloading. Objects are a way of implementing protocols without needing to know the details of the object that implements the protocol, even at runtime. Polymorphic code in OO systems is a runt…

Since Haskell is statically typed, I think it's a feature, not a bug, that type parametricity is implemented at compile time.

Also, I think what you're describing is the difference between parametric polymorphism and ad-hoc polymorphism.

Re: Why isn't Haskell popular in industry?

#52

Post by jrockway »

bguthrie wrote: post #50
jrockway wrote: post #46

Earlier quoted context omitted.

Take monads. The only way to "get" monads is to realize that they are just sections of the program that are imperative. Not really. Monadic function composition is just like regular composition, except that the programmer is given the ability to make "f of g of x" do something more than just pipe the result of g(x) into f. This can look like imperative programming, but it's still purely functional. If you're willing…

I have no idea what a Kleisli arrow is, and a simple Google search points me right back in the direction of the HaskellWiki. They may be a perfectly simple concept, but if they are, then the term is not in widespread use. One of the major problems with explaining monads is that programmers who understand them frequently attempt to explain them by using terms even less well-understood than "monad". You get points for…

A Kleisli arrow is just an arrow that works like a monad:

    -- | Kleisli arrows of a monad.

    newtype Kleisli m a b = Kleisli { runKleisli :: a -> m b }

    instance Monad m => Category (Kleisli m) where
           id = Kleisli return
           (Kleisli f) . (Kleisli g) = Kleisli (\b -> g b >>= f)
I only brought it up to show that we can use the same operator, Control.Category.., to compose functions, monads, and arrows and that they are not all that different from each other.

(It's also worth noting that every language has their own language-specific terminology. If I Google for "std::string", I am only going to find C++ results, despite the fact that strings are a generic concept. If I search for "IEnumerable", I am only going to get C# results, despite the fact that enumerations are a generic concept.

Similarly, not many languages think of programming in terms of arrows and objects and categories, so you don't see many results for "Kleisli arrow" outside of the Haskell community.

But http://en.wikipedia.org/wiki/Kleisli_category is to category theoretical monads as Kleisli arrow is to Monad in Haskell.)

Re: Why isn't Haskell popular in industry?

#53

Post by Flow »

loewenskind wrote: post #44
rimantas wrote: post #42

Not to answer the question, but I can provide some reasons why I am not going to learn Haskell. I must say up front that I know next to nothing about the language, and my reason my sound very irrational, superficial and plain silly, however: it just looks ugly. That's it. I cannot imagine myself sitting all day and staring (or writing) something that looks like explosion on a regexp factory with ruins of Perl fallen…

Really? How beautiful it is is exactly what keeps drawing me to Haskell even though I have more invested in the dynamic language camp. >max = head . sort Due to the laziness, the above will find the max entry in O(n) time, just like your hand written loop would. How can you not find that beautiful? Now I do agree that they often seem to use too many symbols that look like other symbols but the few times I've investig…

You mean max = last . sort ?

Re: Why isn't Haskell popular in industry?

#54

Post by naradaellis »

rimantas wrote: post #42

Not to answer the question, but I can provide some reasons why I am not going to learn Haskell. I must say up front that I know next to nothing about the language, and my reason my sound very irrational, superficial and plain silly, however: it just looks ugly. That's it. I cannot imagine myself sitting all day and staring (or writing) something that looks like explosion on a regexp factory with ruins of Perl fallen…

Love the syntax myself. Even before I knew anything about it, the resemblance to maths was very appealing.

Its even better when you understand it more. The syntax brilliantly expresses the fact that you're essentially working with a computerized lambda calculus.

Re: Why isn't Haskell popular in industry?

#55

Post by tkahn6 »

bguthrie wrote: post #50
jrockway wrote: post #46

Earlier quoted context omitted.

Take monads. The only way to "get" monads is to realize that they are just sections of the program that are imperative. Not really. Monadic function composition is just like regular composition, except that the programmer is given the ability to make "f of g of x" do something more than just pipe the result of g(x) into f. This can look like imperative programming, but it's still purely functional. If you're willing…

I have no idea what a Kleisli arrow is, and a simple Google search points me right back in the direction of the HaskellWiki. They may be a perfectly simple concept, but if they are, then the term is not in widespread use. One of the major problems with explaining monads is that programmers who understand them frequently attempt to explain them by using terms even less well-understood than "monad". You get points for…

The main thing to take away is that:

When a function uses global state to compute a value, it's like the global state is an argument to the function.

When a function modifies global state, it's like it returns both the value it computes and the modified global state.

If you're interested more you can read http://research.microsoft.com/en-us/um/people/simonpj/papers... which I believe is the original paper introducing monads into Haskell. The first 11 pages are very approachable and give you the rational for why monads are necessary in Haskell and what they're for.

Re: Why isn't Haskell popular in industry?

#56

Post by jrockway »

watmough wrote: post #8
theli0nheart wrote: post #2

Every language has a catalyst that pushes it from obscurity into mainstream use. Whether it be a project (Ruby on Rails), a programmer (Linus Torvalds -> C), a company (Google -> Python), or a library (Boost -> C++), there is always a force behind adoption. Most languages undergo a "fad period", where it's hip and cool to write in it and people just do it because other people do it. Clojure is going through this righ…

This reddit post tells me why Haskell isn't that popular. http://www.reddit.com/r/haskell/comments/cs54i/how_would_you... Writing a quick directory traversal function should be a no-brainer in any reasonably general-purpose language. The fact that the above reddit thread is jam-packed with the ins-and-outs of doing this simple task in Haskell tells me that Haskell may be great for some things, but it's probably not g…

The problem with that Reddit post is that it would take a long time to write du, and Reddit users don't have that long of an attention span. Some people are being nice and trying to answer, but nobody took enough time (say, a week of work) to generate a really good answer.

If you asked any question in the form of, "how do I write in ", and you aren't paying for a week of someone's time to get you a really good answer, you aren't going to get a really good answer. It has nothing to do with Haskell. The reality is that programming involves trial, error, and iteration. People on Reddit can give you good first-drafts, but the final product is up to you. (If you asked, "how can I write du in C", then someone could just paste the source code. But du isn't necessarily the best implementation of du.)

I've written some directory traversal code in Haskell for a work project, and I didn't find it to be particularly mind-bending or difficult. I did it the same way I would have in Perl or any other language; visit directory, run my computation, collect the answer, recurse.

Re: Why isn't Haskell popular in industry?

#57

Post by tkahn6 »

naradaellis wrote: post #41
wisty wrote: post #35

Earlier quoted context omitted.

achieving anything practical using purely functional code remains extremely difficult ... Excel is pretty much a functional language (though it is a little disabled), and people do amazing things in it. The problem isn't that functional languages are hard. They are a bit different, but good code is often fairly functional anyway. The problem is that most of the community seems to be obsessed with showing that functio…

Perhaps the reason that Haskellers don't describe monads as "just sections of the program that are imperative" is because that statement is _not_ true. A monad is a very nice container abstraction - period. The IO part of Haskell just happens to leverage monads. One of the benefits of which is an explicit marking of impure methods in the type signature, but there are others. Monads are used in plenty of purely functi…

Can you give an example of where monads are not used to interact with stateful things? That would be helpful to me.

Re: Why isn't Haskell popular in industry?

#58

Post by [deleted] »

gaius wrote: post #31
stephenjudkins wrote: post #21

I think there are a couple reason. Haskell is a significant departure from most other languages commonly used by industrial programmers. It's a relatively shallow learning curve from Java to Python to JavaScript, but making the leap to a pure functional language is very difficult. Path-dependence plays a huge part here. This isn't just a matter of "people being afraid of what's different" as the article suggests; the…

Another, more important reason, is that Haskell is too intellectually demanding for most industrial programmers. t While that's often stated as a reason, I don't believe it myself, simply on the grounds that anyone smart enough to use C++ "in anger" is smart enough to learn any language. The reason that Haskell isn't popular (IMHO) is that a lot of programming isn't clever algorithms, it's forms (interfaces for getti…

[deleted]

Re: Why isn't Haskell popular in industry?

#59

Post by jamii »

gaius wrote: post #31
stephenjudkins wrote: post #21

I think there are a couple reason. Haskell is a significant departure from most other languages commonly used by industrial programmers. It's a relatively shallow learning curve from Java to Python to JavaScript, but making the leap to a pure functional language is very difficult. Path-dependence plays a huge part here. This isn't just a matter of "people being afraid of what's different" as the article suggests; the…

Another, more important reason, is that Haskell is too intellectually demanding for most industrial programmers. t While that's often stated as a reason, I don't believe it myself, simply on the grounds that anyone smart enough to use C++ "in anger" is smart enough to learn any language. The reason that Haskell isn't popular (IMHO) is that a lot of programming isn't clever algorithms, it's forms (interfaces for getti…

> it's forms (interfaces for getting data into databases) and reports (interfaces for getting data out of databases)

Well, with formlets and takusen you're pretty much sorted.

http://haskell.org/haskellwiki/Formlets

http://blog.codersbase.com/2010/08/takusen-tutorial-part-1-h...

Re: Why isn't Haskell popular in industry?

#60

Post by jamii »

tkahn6 wrote: post #57
naradaellis wrote: post #41

Earlier quoted context omitted.

Perhaps the reason that Haskellers don't describe monads as "just sections of the program that are imperative" is because that statement is _not_ true. A monad is a very nice container abstraction - period. The IO part of Haskell just happens to leverage monads. One of the benefits of which is an explicit marking of impure methods in the type signature, but there are others. Monads are used in plenty of purely functi…

Can you give an example of where monads are not used to interact with stateful things? That would be helpful to me.

PFP uses monads to represent probability distributions.

http://web.engr.oregonstate.edu/~erwig/pfp/

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