way better exercises

Akuli · Akuli · commit d97dff1cad04 · 2017-01-05T22:31:44.000+02:00
diff --git a/answers.md b/answers.md
@@ -251,39 +251,58 @@ These are answers for exercises in the chapters. In programming, there's always
 
 ## Defining functions
 
-1. Use `-value` (it works just like `-1`) to get the negative in
-    the abs function, and for loops in the other two functions.
+1. The problem with the first example is that name is a local variable.
+    I explained how to fix this in [the output section](defining-functions.md#output):
 
     ```py
-    def my_abs(value):
-        if value < 0:
-            return -value
-        # actually, this else is useless because returning ends the
-        # function anyway
-        else:
-            return value
-
-    def my_any(a_list):  # don't call this "list", see summary in the Lists chapter
-        for item in a_list:
-            if item:
-                return True    # ends the function
-        return False
-
-    def my_all(a_list):
-        for item in a_list:
-            if not item:
-                return False
-        return True
+    def ask_name():
+        name = input("Enter your name: ")
+        return name
+    
+    print("Your name is", ask_name())
+
+2. If you run the next example, you get something like this:
+
+        <function get_greeting at 0xb73a0a04>
+
+    The problem is that we print the actual `get_greeting` function,
+    but we need to **call** it like `get_greeting()`:
+
+    ```py
+    def get_greeting():
+        return "Hello World!"
+    
+    print(get_greeting())
+    ```
+
+3. See [the return or print section](defining-functions.html#return-or-print).
+
+    The greet function prints a greeting.
+
+    ```py
+    >>> greet("World")
+    Hello World
+    >>> 
     ```
 
-2. Like this:
+    But it also returns None because we don't tell it to return anything else.
 
     ```py
-    def print_box(message, character='*'):
-        number_of_characters = len(message) + 4
-        print(character * number_of_characters)
-        print(character, message, character)
-        print(character * number_of_characters)
+    >>> return_value = greet("World")
+    Hello World
+    >>> print(return_value)
+    None
+    >>> 
+    ```
+
+    This code from the exercise does the same thing as the code above
+    does, but without a temporary `return_value` variable:
+
+    ```py
+    >>> print(greet("World"))
+    Hello World
+    None
+    >>> 
     ```
 
 ***
diff --git a/defining-functions.md b/defining-functions.md
@@ -489,70 +489,42 @@ print("Your favorite color is %s!" % choice)
 
 ## Exercises
 
-**TODO:** more exercises.
-
-**There is a lot to learn about functions, and I don't expect you to
-learn everything at once.** However, there's also lots of free Python
-exercises about defining functions you can do. Do many of them and
-spend time with them until you're familiar with defining functions.
-
-1. The box printing function doesn't really print a box, it prints a
-    message between two lines.
-
-        ************
-        Hello World!
-        ************
-
-    Modify it to print an actual box:
-
-        ****************
-        * Hello World! *
-        ****************
-
-2. Python comes with many built-in functions. Some of the simplest ones
-    are abs, all and any. They can be used like this:
-
-    - abs returns the absolute value of its only argument.
-
-        ```py
-        >>> abs(1)
-        1
-        >>> abs(-1)
-        1
-        >>> 
-        ```
-
-    - any returns True if one or more of the elements of a list is true,
-        and False otherwise.
-
-        ```py
-        >>> any([True, False, True])
-        True
-        >>> any([False, False, False])
-        False
-        >>> 
-        ```
-
-    - all returns True if all elements of a list are true, and False
-        otherwise.
-
-        ```py
-        >>> all([True, True, True])
-        True
-        >>> all([True, False, True])
-        False
-        >>> 
-        ```
-
-    Define functions `my_abs`, `my_all` and `my_any` that work the same
-    way without using the built-in functions. Then run the program with
-    IDLE, or with `py -i file.py` on Windows or `python3 -i file.py` on
-    other operating systems. Try the above examples with your
-    functions.
-
-2. Find more exercises about defining functions online.
-
-Answers for the first and second exercise are [here](answers.md).
+**There are many things to learn about functions, and I don't expect
+you to learn everything at once.** However, there are also many free
+exercises about defining functions you can do.
+
+1. What's wrong with this code?
+
+    ```py
+    def ask_name():
+        name = input("Enter your name: ")
+
+    ask_name()
+    print("Your name is", name)
+    ```
+
+2. How about this code?
+
+    ```py
+    def get_greeting():
+        return "Hello World!"
+
+    print(get_greeting)
+    ```
+
+3. Why does this print None after greeting the world?
+
+    ```py
+    def greet(target):
+        print("Hello", target)
+
+    print(greet("World"))
+    ```
+
+4. Find more exercises about defining functions online.
+
+Answers for the first, second and third exercise are
+[here](answers.md#defining-functions).
 
 ***
 
