[Haskell-beginners] Help - I'm completely lost with building a really simple app with Snap and Groundhog

[Peter Harpending]

On Sat, Jun 20, 2015 at 09:54:27PM +0200, Matthias Beyer wrote:
> I am learning Haskell by trying to implement a really simple CRUD like
> web app with Snap and Groundhog - and I'm completely lost, cannot get
> it to work.

Since you seem to know what all of those things are, I'm going to assume
you have some background in imperative programming. This assumption is
backed by your GitHub history.

I'm guessing, after the initial few languages, with most programming
languages you've encountered thus far, you can learn a new one in a week
or two.

Haskell isn't like other languages. It requires a fundamentally
different manner of thinking about your program. It's like learning to
program all over again. It is worth it, I promise.

As for learning Haskell, Chris Allen's tutorial has links to resources
covering everything under the sun:
<https://github.com/bitemyapp/learnhaskell>.

Now, regarding your actual question: what's wrong with the code you have
posted?

1. First of all, your dependencies are way too strict in your cabal
   file. In fact, most of them conflict. I couldn't even run `cabal
   install`.

   If you want to make sure the packages play together nicely, you
   should use Stackage <http://www.stackage.org>.

2. Nobody uses old versions of base anymore. You don't need that
   old-base stuff.

3. Your cabal file needs a default-language field.

4. Snap is a bit labor-intensive. Yesod <http://www.yesodweb.com> is
   much more well-suited for non-trivial web applications.

Once I cleaned up the cabal file, I was able to get the standard Hello,
World Snap application running on localhost.

I forked your repository on GitHub. You can see the changes I made here:
<https://github.com/matthiasbeyer/rate.hs/compare/master...pharpend:master>. Note
that I am using GHC 7.10, which is the latest version. You might be on
an old version of GHC, in which case, you should do the following:

    rm cabal.config
    cabal install
    cabal freeze

To run the application, I just used `cabal run`.

Peter Harpending
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