5 ms·

Is Haskell a Good Choice for Web Applications? (2009)

93 points by dmitriy_ko 15y ago

deleted 15y ago
[deleted]
- joe_fishfish 15y ago
  Coding in Haskell is not like coding in a more imperative language like Python or Java. Haskell is incredibly terse, and most of the work is done in your mind, trying to figure out exactly how best to declare what you're trying to achieve. Once the thinking part is complete you can usually express what you're trying to do in less than ten lines.
- steeleduncan 15y ago
  From his article I imagine it was 400 hours reading documentation and 100 hours coding. Besides, 2500 lines of Haskell is likely to be far more functional than 2500 lines of PHP.
  - TeMPOraL 15y ago
    > Besides, 2500 lines of Haskell is likely to be far more functional than 2500 lines of PHP. I guess it's true in both meanings of word 'functional' ;).
danieldk 15y ago
Please update the title to indicate that this was written in 2009. In the meanwhile, Haskell has gained (besides Happstack) two excellent web frameworks: Snap and Yesod. One of the points of critique has been addressed now is database access. For instance, Persistent provides type-safe database access: http://www.yesodweb.com/book/persistent http://www.yesodweb.com/book/persistent The author also mentions the problem that exceptions can only be caught in the IO monad. But this has become less of a problem, since more people started using monad transformers (such as ErrorT) to add error handling to their monads. ErrorT allows you to catch exceptions within that monad. For instance, quoting from one of my own projects: readEntry :: MonadIO m => Corpus -> String -> ErrorT CorpusError m Text readEntry is a function that takes a Corpus and a String, and returns Text in a monad of the class MonadIO if the function is successful. Otherwise it reports errors in the form of a CorpusError. You could now, for instance, run this function with runErrorT, and it will return an ordinary Either value in the given monad (Left CorpusError in the case of an error, Right Text when the call is successful).
- ps8ed 15y ago
  Also, if you aren't wedded to SQL, Haskell now has acid-state, a memory resident database written in Haskell (formerly happstack-state).
  - gujk 15y ago
    How does a memory resident database satisfy the D in ACID?
    - scottostler 15y ago
      Presumably it writes to a transaction log, and is memory-resident in the same sense that Redis is. Which is to say that the dataset is kept entirely in memory, but also has a persistent representation on disk.
    - jfoutz 15y ago
      IIRC happstack-state has a journaling system. You don't have the state on disk, but you can reconstruct it. you could also journal to a remote machine for a live failover.
sp00nman 15y ago
How secure are these Haskell web frameworks? (snap, happstack, etc.). Without a django and rails level of exposure, presumably they have quite a few holes still?
- tikhonj 15y ago
  I don't know about their maturity, but I think Haskell's type system and purity would help with security. It doesn't have anything like `eval` and is much less tolerant of weird input by default than dynamically typed languages (at least in my experience). Having no or limited state also helps--bad input and other mistakes tend to be more localized when they can't possibly change anything else in the program. If you're really crazy about security, then I suspect the Haskell code would also be much easier to analyze and verify.
  - danieldk 15y ago
    Also, many underlying components are tested using QuickCheck. QuickCheck allows you to verify that the properties of functions hold under random input. Of course, since such checking is used when the number of possible inputs is too large to check (or infinite), it is not watertight. But it helps tremendously in uncovering bugs.
- losvedir 15y ago
  Well, one feature that Yesod has really been focused on are type-safe URLs[1]. I imagine this would provide some level of security benefit as the framework knows "Ah, in this GET request we should have a Date, an Integer, a UserID, etc". The implementation may still have bugs, I suppose, but you can be sure that it's at least being heavily thought about. I imagine forms may work the same way, though I'm not sure about that. [1] http://www.yesodweb.com/home/snoyberg/blogs/2011/08/shakespeare/new-shakespeare-chapter.ditamap?nav=type-safe-urls http://www.yesodweb.com/home/snoyberg/blogs/2011/08/shakespe...
  - joeyh 15y ago
    Yesod also has automatic html-escaping of strings, enforced at the type level. You have to explicitly tell it when a value is raw html, to avoid XSS. It also has automatic XSRF prevention.
dustingetz 15y ago
the source link[1] doesn't work for me. anyone know where i can find this document? [1] http://jekor.com/vocabulink/vocabulink.pdf http://jekor.com/vocabulink/vocabulink.pdf
- dowskitest 15y ago
  It worked here, but only when I did a right-click and "save as".
deleted 15y ago
[deleted]
savoy11 15y ago
Please, do not update the title. It does not matter if the year is 2009. The answer is no. For ultra-fast web applications written in weird functional languages - check out the forum at news.ycombinator.com
jnbiche 15y ago
As someone who's learning Haskell, I read the post because I'm interested in the language's capabilities in the web arena. But your site itself is brilliant! You are really on to something with vocabulink.com. I've formally studied 10 human languages, of which I can speak/write/read 3 fluently, and have passive understanding of another 2-3. People often ask me how I learn languages, and a good part of my answer is very similar to what you are doing with vocabulink. As you've discovered, the key is to use vivid, even silly, mnemonic devices. Building up a large vocabulary is key to learning a language. Don't waste your money on flashy tools like Rosetta Stone -- they don't work for most people above the age of 8 or 10. Adults learn differently than children. So if someone out there is looking to learn a foreign language, my recommendation is to combine vocabulink's approach to build up a large vocabulary, and find the best concise grammar available for your target language. If you don't remember grammar fundamentals (e.g., what's a prepositional phrase, direct object, relative pronoun, etc.), then you need to find a good book in your native language to review those concepts. In any case, cool concept for a web site. Sorry for the off-topic post. Thanks for telling us about your experiences with Haskell. I do think that Haskell web capabilities have come a long way since 2009, particularly Yesod (I'm not familiar with Snap).
scarmig 15y ago
I've been wondering how well-suited FRP (implemented either in Haskell or something else) is for back-end technology. It seems like it might be overkill, but it does have a certain conceptual elegance to it. Anyone play around with this idea?
- davorak 15y ago
  Check out elm: http://elm-lang.org/Elm.elm http://elm-lang.org/Elm.elm Recent reddit conversation: http://www.reddit.com/r/haskell/comments/mwbvj/elm_functional_reactive_webprogramming_compiles/ http://www.reddit.com/r/haskell/comments/mwbvj/elm_functiona...

93 points by dmitriy_ko 15y ago

deleted 15y ago

[deleted]

joe_fishfish 15y ago
Coding in Haskell is not like coding in a more imperative language like Python or Java. Haskell is incredibly terse, and most of the work is done in your mind, trying to figure out exactly how best to declare what you're trying to achieve. Once the thinking part is complete you can usually express what you're trying to do in less than ten lines.
steeleduncan 15y ago
From his article I imagine it was 400 hours reading documentation and 100 hours coding. Besides, 2500 lines of Haskell is likely to be far more functional than 2500 lines of PHP.
- TeMPOraL 15y ago
  > Besides, 2500 lines of Haskell is likely to be far more functional than 2500 lines of PHP. I guess it's true in both meanings of word 'functional' ;).

danieldk 15y ago

Please update the title to indicate that this was written in 2009. In the meanwhile, Haskell has gained (besides Happstack) two excellent web frameworks: Snap and Yesod. One of the points of critique has been addressed now is database access. For instance, Persistent provides type-safe database access: http://www.yesodweb.com/book/persistent http://www.yesodweb.com/book/persistent The author also mentions the problem that exceptions can only be caught in the IO monad. But this has become less of a problem, since more people started using monad transformers (such as ErrorT) to add error handling to their monads. ErrorT allows you to catch exceptions within that monad. For instance, quoting from one of my own projects: readEntry :: MonadIO m => Corpus -> String -> ErrorT CorpusError m Text readEntry is a function that takes a Corpus and a String, and returns Text in a monad of the class MonadIO if the function is successful. Otherwise it reports errors in the form of a CorpusError. You could now, for instance, run this function with runErrorT, and it will return an ordinary Either value in the given monad (Left CorpusError in the case of an error, Right Text when the call is successful).

ps8ed 15y ago
Also, if you aren't wedded to SQL, Haskell now has acid-state, a memory resident database written in Haskell (formerly happstack-state).
- gujk 15y ago
  How does a memory resident database satisfy the D in ACID?
  - scottostler 15y ago
    Presumably it writes to a transaction log, and is memory-resident in the same sense that Redis is. Which is to say that the dataset is kept entirely in memory, but also has a persistent representation on disk.
  - jfoutz 15y ago
    IIRC happstack-state has a journaling system. You don't have the state on disk, but you can reconstruct it. you could also journal to a remote machine for a live failover.

sp00nman 15y ago

How secure are these Haskell web frameworks? (snap, happstack, etc.). Without a django and rails level of exposure, presumably they have quite a few holes still?

tikhonj 15y ago
I don't know about their maturity, but I think Haskell's type system and purity would help with security. It doesn't have anything like `eval` and is much less tolerant of weird input by default than dynamically typed languages (at least in my experience). Having no or limited state also helps--bad input and other mistakes tend to be more localized when they can't possibly change anything else in the program. If you're really crazy about security, then I suspect the Haskell code would also be much easier to analyze and verify.
- danieldk 15y ago
  Also, many underlying components are tested using QuickCheck. QuickCheck allows you to verify that the properties of functions hold under random input. Of course, since such checking is used when the number of possible inputs is too large to check (or infinite), it is not watertight. But it helps tremendously in uncovering bugs.
losvedir 15y ago
Well, one feature that Yesod has really been focused on are type-safe URLs[1]. I imagine this would provide some level of security benefit as the framework knows "Ah, in this GET request we should have a Date, an Integer, a UserID, etc". The implementation may still have bugs, I suppose, but you can be sure that it's at least being heavily thought about. I imagine forms may work the same way, though I'm not sure about that. [1] http://www.yesodweb.com/home/snoyberg/blogs/2011/08/shakespeare/new-shakespeare-chapter.ditamap?nav=type-safe-urls http://www.yesodweb.com/home/snoyberg/blogs/2011/08/shakespe...
- joeyh 15y ago
  Yesod also has automatic html-escaping of strings, enforced at the type level. You have to explicitly tell it when a value is raw html, to avoid XSS. It also has automatic XSRF prevention.

dustingetz 15y ago

the source link[1] doesn't work for me. anyone know where i can find this document? [1] http://jekor.com/vocabulink/vocabulink.pdf http://jekor.com/vocabulink/vocabulink.pdf

dowskitest 15y ago
It worked here, but only when I did a right-click and "save as".

deleted 15y ago

[deleted]

savoy11 15y ago

Please, do not update the title. It does not matter if the year is 2009. The answer is no. For ultra-fast web applications written in weird functional languages - check out the forum at news.ycombinator.com

jnbiche 15y ago

As someone who's learning Haskell, I read the post because I'm interested in the language's capabilities in the web arena. But your site itself is brilliant! You are really on to something with vocabulink.com. I've formally studied 10 human languages, of which I can speak/write/read 3 fluently, and have passive understanding of another 2-3. People often ask me how I learn languages, and a good part of my answer is very similar to what you are doing with vocabulink. As you've discovered, the key is to use vivid, even silly, mnemonic devices. Building up a large vocabulary is key to learning a language. Don't waste your money on flashy tools like Rosetta Stone -- they don't work for most people above the age of 8 or 10. Adults learn differently than children. So if someone out there is looking to learn a foreign language, my recommendation is to combine vocabulink's approach to build up a large vocabulary, and find the best concise grammar available for your target language. If you don't remember grammar fundamentals (e.g., what's a prepositional phrase, direct object, relative pronoun, etc.), then you need to find a good book in your native language to review those concepts. In any case, cool concept for a web site. Sorry for the off-topic post. Thanks for telling us about your experiences with Haskell. I do think that Haskell web capabilities have come a long way since 2009, particularly Yesod (I'm not familiar with Snap).

scarmig 15y ago

I've been wondering how well-suited FRP (implemented either in Haskell or something else) is for back-end technology. It seems like it might be overkill, but it does have a certain conceptual elegance to it. Anyone play around with this idea?

davorak 15y ago
Check out elm: http://elm-lang.org/Elm.elm http://elm-lang.org/Elm.elm Recent reddit conversation: http://www.reddit.com/r/haskell/comments/mwbvj/elm_functional_reactive_webprogramming_compiles/ http://www.reddit.com/r/haskell/comments/mwbvj/elm_functiona...