added tutorial on xml parsing

doc/tutorial1.clj

@@ -0,0 +1,46 @@
+(ns tutorial1
+  (:use
+   [eu.dnetlib.clojure.clarsec]
+   [eu.dnetlib.clojure.monad]))
+
+;; Parsing simplified XML:
+;;
+;; Sample Input:
+
+(def input
+     "    <library>
+              <book>
+                  <title>Hello</title>
+                  <author>Knuth</author>
+              </book>
+              <book>
+                  <title>World</title>
+                  <author>Knuth</author>
+              </book>
+              <book>
+                  <title>World</title>
+                  <author>Knuth</author>
+              </book>
+          </library>")
+
+(defn arrows [p] (between (symb "<") (symb ">") p))
+
+(def open-tag (arrows identifier))
+(defn close-tag [expect-name] (arrows (symb (str "/" expect-name))))
+
+(defn element [p]
+  (let-bind [tag-name open-tag
+             contents p
+             _ (close-tag tag-name)]
+            (result {(keyword tag-name) contents})))
+
+(def xml
+     (let [list$ #(flatten (apply list %&))]
+       (element
+        (<|> (<$> #(apply merge-with list$ %) (many1 (lazy xml)))
+             (stringify (many letter))))))
+
+(defn -main []
+    (println (:value (parse xml input))))
+
+;; (-main)