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

[Michael Litchard]

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":_) = "ש×~\×~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