fix composition example

Author: despadam

11_functional_programming.ipynb

@@ -422,7 +422,7 @@
     "\n",
     "<div class=\"alert alert-block alert-warning\">\n",
     "    <h4><b>Question</b></h4>\n",
-    "    Inside the solution function below, write the solution of equation <code>x^2 + y^2</code>, using lambda expressions.\n",
+    "    Inside the solution function below, write the solution of equation <code>x^2 + y^2</code>, using composition.\n",
     "</div>"
    ]
   },
@@ -444,7 +444,7 @@
     "%%ipytest\n",
     "\n",
     "def solution_composition(x: int, y: int):\n",
-    "    \"\"\"A function that solves the equation x^2 + y^2, using lambda functions.\n",
+    "    \"\"\"A function that solves the equation x^2 + y^2, using composition.\n",
     "\n",
     "    Args:\n",
     "        x: the first integer\n",

tutorial/tests/test_11_functional_programming.py

@@ -42,10 +42,11 @@ def reference_composition(x, y):
     def square(x: int) -> int:
         return x * x
 
-    def sum(x: int, y: int) -> int:
+    def add(x: int, y: int) -> int:
         return x + y
 
-    eq = lambda x, y: sum(square(x), square(y))
+    def eq(x: int, y: int) -> int:
+        return add(square(x), square(y))
 
     return eq(x, y)