[Haskell-beginners] Having fun with yesod, and a few questions came up.

15 Jul 2010

      I'm playing with yesod http://docs.yesodweb.com/yesod/,  and I have a
few questions:

Here's an excerpt from yesod/tutorial/i18n.lhs

**NOTE: This tutorial requires the development version of Yesod
(version 0.4.0). The [tutorial main page]($root/yesod/tutorial/) has
instructions on setting up your environment.**

Where is $root?
I thought it was where yesod-examples-0.4.0 was installed. But if this
is the case, I'm not finding these instructions. This makes me think I
am confused about the directory $root represents.

I was playing around with the code and made some changes. Here is the
line in question, with the complete code below for context.
...
instance Yesod I18N where
    approot _ = ""
This does what I expect it to do, it runs the program when I open up
http://my.blog.server/

however, I wanted to see what would happen if I played around with it
a little bit. I want the same program to run when I point my browser
to http://my.blog.server/blog

so I made this change
...
approot _ = "/blog"
but now when I point my browser to http://my.blog.server/blog it gets
re-written to http:/my.blog.server/blog/blog
and then this error message
Not Found
/blog/blog

Not sure what is going on here, could someone enlighten me?

---
title: Multi-lingual -- Tutorials -- Yesod
---
**NOTE: This tutorial requires the development version of Yesod
(version 0.4.0). The [tutorial main page]($root/yesod/tutorial/) has
instructions on setting up your environment.**
...
{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeFamilies #-}
...
import Yesod
import Data.Monoid (mempty)
...
data I18N = I18N
...
mkYesod "I18N" [$parseRoutes|
/            HomepageR GET
/set/#String SetLangR  GET
|]
...
instance Yesod I18N where
    approot _ = "/blog"
...
getHomepageR :: Handler I18N RepHtml
getHomepageR = do
    ls <- languages
    let hello = chooseHello ls
    let choices =
            [ ("en", "English")
            , ("es", "Spanish")
            , ("he", "Hebrew")
            ]
    applyLayout "I18N Homepage" mempty [$hamlet|
%h1 $hello$
%p In other languages:
%ul
    $forall choices choice
        %li
            %a!href=@SetLangR.fst.choice@ $snd.choice$
|]
...
chooseHello :: [String] -> String
chooseHello [] = "Hello"
chooseHello ("he":_) = "×©×~\×~U×~]"
chooseHello ("es":_) = "Hola"
chooseHello (_:rest) = chooseHello rest
...
getSetLangR :: String -> Handler I18N ()
getSetLangR lang = do
    setLanguage lang
    redirect RedirectTemporary HomepageR
...
main :: IO ()
main = basicHandler 3000 I18N

[Haskell-beginners] Having fun with yesod, and a few questions came up.

Michael Litchard