Snap for Beginners: Haskell Web Development

by biscarch • 12 years ago

159 83 12 years ago

boothead6• 12 years ago

Currently heading up a team of awesomely smart people building our back end in Haskell on snap. AMA!

bwilliams2• 12 years ago

"the development SPEED of ruby with the SAFETY of STATIC TYPING" sounds kind of sketchy. Would you say that title is true?

ixmatus2• 12 years ago

Not only true but faster because less time spent debugging.

boothead6• 12 years ago

What you find if you're doing it right is not only that you get the safety of static typing, but also that the types often lead you towards to solution.

Abstractions in Haskell are smaller, more universal and composable than those of say ruby or python. For example the very simple idea of a Monoid (essentially concatenation) can be found in most places either explicitly or if you squint a bit, and once you recognise it a whole set of properties and behaviours can be reused.

Also once the structure is in place, they types make for very safe re-factoring and assurance that you haven't broken anything.

The only thing that's probably slower than ruby in Haskell is, unfortunately, learning it in the first place :-)

msluyter• 12 years ago

How long do you think it'd take for a reasonably decent developer with no prior experience to pick up and become competent with Haskell and Snap?

copergi4• 12 years ago

I don't have a lot of data points, but for the one PHP developer I had learn haskell by writing a webapp in it, 6 months from "never seen haskell before" to "feels comfortable working solo and doesn't need help". The first 80% comes pretty quick, but not needing someone to answer questions takes a while.

nnutter2• 12 years ago

How do you plan to deploy your backend? Are there tools to do it? Is it just rsyncing a cabal sandbox to another machine? What about compiling and stuff? (I've barely made my way through LYHGG.)

copergi4• 12 years ago

I used to just scp the binary up to the servers. They don't need any haskell stuff installed or anything like that. Recently I made it so they grab the latest binary off of S3 on bootup and when I run an update script. So now I just upload the binary to S3 instead.

begriffs• 12 years ago

You can deploy Snap apps to Heroku pretty easily.

https://github.com/begriffs/heroku-buildpack-ghc

boothead6• 12 years ago

So we started with a git subtree merge of all the dependent projects and then a script to build a docker container, with physical infrastructure managed by ansible. It now looks more like we're going to use NixOs and NixOps - which are awesome!

nnutter2• 12 years ago

Are there (good) tools to help with refactoring Haskell? To me this seems like one of the benefits of a statically typed language (I've almost entirely worked in Perl).

tinco• 12 years ago

Not as good as for example for C#, but not as bad as for example Ruby.

I have a plugin for Sublime that complains when something is broken, or a dependency is missing. The typesystem is so strong that usually when it compiles, it works.

So my process for refactoring is basically changing typesystems, and having the compiler check my changes until it works again.

Note that this thinks of Ruby as bad only in IDE aspect. Refactoring Ruby is actually quite enjoyable as Ruby is so friendly to unit testing. You just move your code and run your tests again.

judk3• 12 years ago

Look up [HaRe the Haskell refactorer]

jcampbell1• 12 years ago

Are there any open source Snap projects that are good to learn from the code?

biscarch• 12 years ago

There is a list of some people using Snap here[1] and some of them are open source. The book also has approximately 8 pre-coded projects that come with it and correlate to the chapters.

[1] http://snapframework.com/faq#is-anyone-using-snap-in-product...

rgbrgb• 12 years ago

Please consider changing the title font. It is very hard on my eyes.

yeukhon• 12 years ago

And also the color contrast.

andrewflnr• 12 years ago

As long as we're talking about the appearance, I had to zoom out to be able to see the text with Firefox 27, and then stuff started moving around like some pieces of it were centered with different methods or something.

BadassFractal2• 12 years ago

Anybody know of solid super-entry level tutorials for starting Web Development with Haskell with less opinionated libraries like Scotty? Something that shows you how to slap together a solid cabal sandboxed ready-to-deploy application that's a mix of Scotty/Persistant/Esqueleto and all the other basics?

Clojure has "Web Development with Clojure" which is basically what I listed above, except for Clojure rather than Haskell.

klrr• 12 years ago

There is this tutorial: http://adit.io/posts/2013-04-15-making-a-website-with-haskel...

Although it uses virthualenv instead of a cabal sandbox.

chrisrogers• 12 years ago

I read that article a few weeks ago in order to get a basic personal site server running on Heroku. I used a standard cabal setup and updated a few things.

end result here, which I think should serve as a good starter point for developing with Scotty:

https://github.com/chrissrogers/chrissrogers.com

For Heroku builds I used the following excellent buildpack

https://github.com/begriffs/heroku-buildpack-ghc

gcb0• 12 years ago

for a true beginner, it starts with an outdated cabal definition for virthualenv/hsenv that has specific old versions. nobody will be able to just copy and paste trhu the tutorial.

but it seems well written if you can get past that point. Most beginners won't though.

egonschiele2• 12 years ago

Post author here. I just updated the post to use cabal sandboxes.

boothead6• 12 years ago

I gave a talk at a Haskell meetup in London this week that covered some of this - the slides won't really be useful standalone, but I could probably re purpose them to a blog post fairly easily if you're interested?

arms• 12 years ago

I know I would be very interested in this.

BadassFractal2• 12 years ago

Would be pretty interested.

pdpi• 12 years ago

Not sure about the OP, but I'd definitely love to read that.

ch0wn• 12 years ago

Please do, that sounds fantastic. Also, which meetup were you speaking at?

octagonal• 12 years ago

Yes Please. Do you have a link to your blog?

crntaylor2• 12 years ago

Sorry I missed the talk! Did it get videoed? They usually are.

jbeja• 12 years ago

I am rading that book right now, is amazing. It makes Clojure so much easy, and the tutorials are well paced as explained.

copergi4• 12 years ago

I can't help you with the tutorials, but snap and happstack are no more opinionated than scotty. They just have documentation and a collection of useful libraries you can use with them.

cgag2• 12 years ago

I just figured out how to do this yesterday, here's the source of my barebones Scott/Persistent/Esqueleto app. All it does is insert some records into the db (sqlite), then runs a server that displays the first entry. (The entry is mixed into the scotty tutorial because I stopped as soon as I got something working). https://github.com/cgag/comments

I may write up a blogpost on getting this far. It's mostly based on this: https://www.fpcomplete.com/school/starting-with-haskell/libr... . I didn't do much beyond figure out explictly using L.fromStrict to deal with conflicting interpretations of overloaded-strings and figuring out how where to put my fillDB and getComments functions in main. I initially tried to call these within the scotty monad, but I think doing it that way would have required learning about monad transformers.

I'm hoping to eventually turn this into a simple disqus alternative that should be lightweight and easy to distribute as a binary.

mightybyte• 12 years ago

At the lowest level, the Snap Framework is not at all opinionated. The base level of the framework is comprised of snap-core and snap-server. snap-core is a web server API roughly on the level of Yesod's wai with maybe a little more slightly higher-level functionality. snap-server is Snap's web server that implements the snap-core API--roughly equivalent to Yesod's warp.

I personally don't understand the draw of scotty because as soon as you want to start doing more substantial web development, you're going to want higher level abstractions. The Snap Framework adds to this in a pretty flexible and not-too-opinionated way with snaplets which are implemented in the snap package. The snap package also contains a few core snaplets that almost every application will want out of the box like sessions, auth, and a snaplet for Heist templating. The Heist part is the only place where the snap package gets opinionated. But you are definitely not locked into using Heist. You could very easily use Yesod's Hamlet, HStringTemplate, hastache, or anything else. Heist just happens to be the direction that the core Snap developers seem to prefer.

sssilver• 12 years ago

The typography makes my eyes bleed.

houzi• 12 years ago

Did you have problems with extremely ugly typefaces in the sample chapter? I had horrible typefaces with bold ligatures. It seemed as if my hinting and sub-pixel rendering had stopped working. There were many errors and warnings in the debugging console as well.

egonschiele2• 12 years ago

Finally! Snap is a great framework but it's been missing a good guide for a while.

MaxGabriel• 12 years ago

Cool, this is really good for Snap. I heard good things about Snap, but a major reason I went to Yesod instead was that it had a book that I could work through (For a Haskell beginner like me, having some structure was important).

codygman2• 12 years ago

I was about to use Yesod instead also, then I came across OP's book.

maxharris• 12 years ago

How does this compare with Meteor? I love Haskell, and if Snap can do the same kind of magic that Meteor does, I'll switch.

codygman2• 12 years ago

Meteor is more for front-end right? I think Snap is mostly for the backend portion of that, however there are some Haskell to Javascript libraries which may enable functionality you get with Meteor (as well as the type safety most know and love).

kazagistar• 12 years ago

Meteor is for both ends at the same time. Most of your code on front end and back end is shared, including database queries, in a safe way.

cies2• 12 years ago

Check out Fay (Haskell to JS). You can scaffold up a test site with Yesod where it integrates with Fay.

https://github.com/yesodweb/yesod-scaffold/tree/postgres-fay

It's not quite Meteor (then I dont believe it is so great), but works today and gives you Haskell from front-to-back.

The Haskell Center IDE of FPComplete is build with Yesod and Fay -- and that is a serious application.

chongli• 12 years ago

While nice it's definitely not for a beginner. This enormous scaffold pulls in so many different things that it'd take a very long time to figure out.

cgag2• 12 years ago

I just started playing with Scotty while I learn, but I'm beginning working on a web app in Haskell and was leaning towards using Snap. I'll almost certainly pick this up. That new IO manager is a beautiful thing.

kayloos• 12 years ago

There's a new web library that extends Scotty with basic session and authenticiation support, called Spock.

I used it for a personal project of mine, which is creating an rss reader resembling the now dead iGoogle (which I loved), and although I had to read a lot of source code to get it to work, I really enjoyed how I worked with it, after figuring out the patterns on how to use it.

It definitely isn't finished, it could use some love by some eager developers, but in my opinion it has the potential to be the best framework out there.

- It extends scotty, so defining routes and control logic is fast and simple - It does not cage you in with a template language, or libraries that you don't want thrown in your face.

For example, I used Scotty with my own templating language I made for fun (hemplate), as well as a validation library I made, which I hope to finish in the near future, (after I get a job).

http://hackage.haskell.org/package/Spock

sudeep1• 12 years ago

why anyone would want to build with snap leaving RoR behind.

copergi4• 12 years ago

Yes, leaving RoR behind is certainly one reason for some people to use snap. But even for people who didn't fall into the rails trap, haskell is much nicer for web development than most languages (PHP, python, java, C#, etc).

acconrad• 12 years ago

Is there a site analogous to the Rails Tutorial e-book, but for Haskell?

Snap for Beginners: Haskell Web Development

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