Added rd grammar

nlp/4_2_Syntactic_Processing.ipynb

@@ -233,12 +233,14 @@
     "\n",
     "We can use the StandfordParser that is integrated in NLTK, but it requires to configure the CLASSPATH, which can be a bit annoying. Instead, we are going to see some demos to understand how grammars work. In case you are interested, you can consult the [manual](http://www.nltk.org/api/nltk.parse.html) to run it.\n",
     "\n",
-    "In the following example, you will run an interactive context-free parser, called [shift-reduce parser](http://www.nltk.org/book/ch08.html).\n",
+    "In the following example, you will run two interactive context-free parser (http://www.nltk.org/book/ch08.html): shift-reduce parser (botton-up) and  recursive descent parser (top-down).\n",
-    "The panel on the left shows the grammar as a list of production rules. The panel on the right contains the stack  and the remaining input.\n",
+    "\n",
+    "\n",
+    "First, we run the shift-reduce parser. The panel on the left shows the grammar as a list of production rules. The panel on the right contains the stack  and the remaining input.\n",
     "\n",
     "You should:\n",
     "* Run pressing 'step' until the sentence is fully analyzed. With each step, the parser either shifts one word onto the stack or reduces two subtrees of the stack into a new subtree.\n",
-    "* Try to act as the parser. Instead of pressing 'step', press  'shift' and 'reduce'. Follow the 'always shift before reduce' rule. It is likely you will reach a state where the parser cannot proceed. You can go back with 'Undo'."
+    "* Try to act as the parser. Instead of pressing 'step', press  'shift' and 'reduce'. Follow the 'always shift before reduce' rule. It is likely you will reach a state where the parser cannot proceed. You can go back with 'Undo'. You can try to change the order of the grammar rules or add new grammar rules."
    ]
   },
   {
@@ -253,6 +255,25 @@
     "srparser_app.app()"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Now we run the recursive descent parser. Observe the different parsing strategies and consult the [book](http://www.nltk.org/api/nltk.parse.html)."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "collapsed": true
+   },
+   "outputs": [],
+   "source": [
+    "from nltk.app import rdparser_app\n",
+    "rdparser_app.app()"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},