Some improvements in the first notebooks

notebooks/julia_basics.ipynb

@@ -147,6 +147,44 @@
     "foo()"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "d18e679d",
+   "metadata": {},
+   "source": [
+    "### A very easy first exercise\n",
+    "\n",
+    "Run the following cell. It contains definitions used later in the notebook."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "81678b3d",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "function why_q1()\n",
+    "    msg = \"\"\"\n",
+    "    In the first line, we assign a variable to a value. In the second line, we assign another variable to the same value. Thus, we have 2 variables associated with the same value. In line 3, we associate y to a new value (re-assignment). Thus, we have 2 variables associated with 2 different values. Variable x is still associated with its original value. Thus, the value at the final line is x=1.\n",
+    "    \"\"\"\n",
+    "    println(msg)\n",
+    "end\n",
+    "function why_q2()\n",
+    "    msg = \"\"\"\n",
+    "    It will be 1 for very similar reasons as in the previous questions: we are reassigning a local variable, not the global variable defined outside the function.\n",
+    "    \"\"\"\n",
+    "    println(msg)\n",
+    "end\n",
+    "function why_q3()\n",
+    "    msg = \"\"\"\n",
+    "    It will be 6. In the returned function f2, x is equal to 2. Thus, when calling f2(3) we compute 2*3.\n",
+    "    \"\"\"\n",
+    "    println(msg)\n",
+    "end\n",
+    "println(\"🥳 Well done! \")"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "92112bd1",
@@ -467,6 +505,24 @@
     "x"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "a2f94960",
+   "metadata": {},
+   "source": [
+    "Run next cell to get an explanation of this question."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "fc562337",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "why_q1()"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "4d2cb752",
@@ -586,6 +642,24 @@
     "x"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "f69108c2",
+   "metadata": {},
+   "source": [
+    "Run next cell to get an explanation of this question."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "05c62aa3",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "why_q2()"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "4fc5eb9b",
@@ -1068,6 +1142,24 @@
     "x"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "062ff145",
+   "metadata": {},
+   "source": [
+    "Run next cell to get an explanation of this question."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "6bf7818e",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "why_q3()"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "bc8e9bcf",
@@ -1257,16 +1349,6 @@
     "squares[2:3] = [4,9]"
    ]
   },
-  {
-   "cell_type": "markdown",
-   "id": "92248ad5",
-   "metadata": {},
-   "source": [
-    "<div class=\"alert alert-block alert-info\">\n",
-    "<b>Tip:</b> Note that Julia array indexing is 1-based (like in Fortran, but unlike C,C++,Python). Love it or hate it. 🙂\n",
-    "</div>"
-   ]
-  },
   {
    "cell_type": "markdown",
    "id": "f64021ab",