Remove semicolon at the end of function declaration, and explains why it is...

Remove semicolon at the end of function declaration, and explains why it is required to add a semicolon at the end of a struct

2-ObjectProgramming/1-Introduction.ipynb

@@ -43,7 +43,7 @@
     "double norm(double v_x, double v_y, double v_z) \n",
     "{ \n",
     "    return std::sqrt( v_x * v_x + v_y * v_y + v_z * v_z ); \n",
-    "};\n",
+    "}\n",
     "\n",
     "{\n",
     "    double v1_x, v1_y, v1_z;\n",
@@ -158,6 +158,41 @@
     "Let's also highlight the `.` syntax which allows to access the attributes of an object (e.g `v1.x`).\n"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### The semicolon at the end of a `struct`\n",
+    "This comes historically from the C, where a `struct` is considered as a type declaration and it allows to do:\n",
+    "\n",
+    "**Xeus-cling issue:** Here cling doesn't manage to compile it but it is accepted rightfully by a full-fledged compiler (see for instance [@Coliru](http://coliru.stacked-crooked.com/a/3b77606ea8082485)):"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "struct Vector\n",
+    "{\n",
+    "    double x;\n",
+    "    double y;\n",
+    "    double z;    \n",
+    "} v1; // Here the struct is declared and at the same time an object v1 is created\n",
+    "\n",
+    "v1.x = 1.;\n",
+    "v1.y = 5.;\n",
+    "v1.z = -2.;"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "This is the reason why a semicolon is always required at the end of a `struct` or a `class` declaration."
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},