[added FromReqURI, tweaked theme.
Jeremy Shaw <jeremy@seereason.com>**20100524232712
 Ignore-this: 348770482360f3e903874f97c430c0d9
] hunk ./Dir.lhs 10
+<div class="source">
hunk ./Dir.lhs 22
+</div>
hunk ./Dir2.lhs 10
+<div class="source">
hunk ./Dir2.lhs 22
+</div>
hunk ./Dirs.lhs 10
+<div class="source">
hunk ./Dirs.lhs 22
+</div>
addfile ./FromReqURI.lhs
hunk ./FromReqURI.lhs 1
+<!--
+
+> {-# LANGUAGE CPP #-}
+
+-->
+
+<h3><a name="FromReqURI"><code>FromReqURI</code>: extending <code>path</code></a></h3>
+
+<p>We can extend path so that we can extract our own types from the path components as well. We simply add an instance to the FromReqURI class: </p>
+
+#ifdef HsColour
+> class FromReqURI a where 
+>     fromReqURI :: String -> Maybe a
+#endif
+
+<p>For example, let's say that we want to create a type to represent subjects we can greet.</p>
+<div class="source">
+
+> module Main where
+>
+> import Control.Monad (msum)
+> import Data.Char (toLower)
+> import Happstack.Server (FromReqURI(..), nullConf, simpleHTTP, ok, dir, path)
+>
+> data Subject = World | Haskell
+>
+> sayHello :: Subject -> String
+> sayHello World   = "Hello, World!"
+> sayHello Haskell = "Greetings, Haskell!"
+>
+
+</div>
+<p>We simple add an instance such as: </p>
+<div class="source">
+
+> instance FromReqURI Subject where
+>     fromReqURI sub =
+>         case map toLower sub of
+>           "haskell" -> Just Haskell
+>           "world"   -> Just World
+>           _         -> Nothing
+>
+
+</div>
+<p>Now when we use <code>path</code> it will extract a value of type <code>Subject</code>.</p>
+<div class="source">
+
+> main :: IO ()
+> main = simpleHTTP nullConf $ msum [ dir "hello" $ path $ \subject -> ok $ (sayHello subject)
+>
+
+</div>
+<p class="source-code">[Source code for the app is <a href="FromReqURI.hs">here.</a>]</p>
+
+<p>Now, if we start the app and point our browser at:  <a href="http://localhost:8000/hello/World">http://localhost:8000/hello/World</a> we get the "Hello, World"". </p>
+<p>if we point it at <a href="http://localhost:8000/hello/Haskell">http://localhost:8000/hello/Haskell</a>, we get "Greetings, Haskell!".</p>
hunk ./HelloWorld.lhs 22
+<div class="source">
hunk ./HelloWorld.lhs 31
+</div>
hunk ./Main.lhs 37
- <li><a href="RouteFilters.html">Routing URLS</a></li>
+ <li><a href="RouteFilters.html">Routing URLS</a>
+  <ol>
+   <li><a href="RouteFilters.html#variable_path_segments">Variable Path Segments</a>
+    <ol>
+     <li><a href="RouteFilters.html#path"><code>path</code></a></li>
+     <li><a href="RouteFilters.html#FromReqURI"><code>FromReqURI</code>: extending <code>path</code></a></li>
+    </ol>
+   </li>
+  </ol>
+ </li>
hunk ./Makefile 6
-DEMOS := Dir.lhs Dir2.lhs Dirs.lhs Path.lhs
+DEMOS := Dir.lhs Dir2.lhs Dirs.lhs Path.lhs FromReqURI.lhs
hunk ./Makefile 13
-RouteFilters.html: MonadPlus.lhs Dir.lhs Dir2.lhs Dirs.lhs Path.lhs
+RouteFilters.html: MonadPlus.lhs Dir.lhs Dir2.lhs Dirs.lhs Path.lhs FromReqURI.lhs
hunk ./Makefile 65
-	sed -n 's/^> \?//p' $^ > $@
+	cpphs --noline $^ | grep -v '{-# LANGUAGE CPP #-}' | sed -n 's/^> \?//p' > $@
+#	cpp -DExtract -traditional-cpp -P $^ | grep -v '{-# OPTIONS_GHC -cpp #-}' | sed -n 's/^> \?//p' > $@
hunk ./MonadPlus.lhs 15
-<code>ServerPartT</code> by using <code>MonadPlus</code>.
-
-<p>In the following example we combine three <code>ServerPartT</code>s
-together using the <code>MonadPlus</code> function.
+<code>ServerPartT</code> by using <code>MonadPlus</code>. Typically
+via the <code>msum</code> function:
hunk ./MonadPlus.lhs 22
+<p>In the following example we combine three <code>ServerPartT</code>s
+together.</p>
+
+<div class="source">
+
hunk ./MonadPlus.lhs 38
+</div>
hunk ./Path.lhs 7
-<h2>Matching on dynamic path segments</h2>
+<h2><a name="variable_path_segments">Matching on variable path segments</a></h2>
hunk ./Path.lhs 9
-<h3><code>path</code></h3>
+<h3><a name="path"><code>path</code></a></h3>
hunk ./Path.lhs 26
+<div class="source">
hunk ./Path.lhs 37
+</div>
hunk ./Path.lhs 39
+
+<p>Now, if we start the app and point our browser at:  <a href="http://localhost:8000/hello/World">http://localhost:8000/hello/World</a> we get the "Hello, World". </p>
+<p>if we point it at <a href="http://localhost:8000/hello/Haskell">http://localhost:8000/hello/Haskell</a>, we get "Hello, Haskell".</p>
hunk ./Path.lhs 43
-<p>Now, if we start the app and point our browser at:  <a href="http://localhost:8000/hello/World">http://localhost:8000/hello/World</a> we get the "Hello, World". <p>if we point it at <a href="http://localhost:8000/hello/Haskell">http://localhost:8000/hello/Haskell</a>, we get "Hello, Haskell".</p>
hunk ./RouteFilters.lhs 28
+#include "FromReqURI.lhs"
hunk ./blog.css 3
-  font-family: Georgia, Serif;
+/*  font-family: Georgia, Serif; */
+  font-family: Sans-serif;
hunk ./blog.css 6
-  width: 30em;
+  width: 50em;
hunk ./blog.css 51
+.source
+{ 
+  background: #eeeeee;
+  padding: 1em;
+ }
+
+