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--- functions [2023/11/03 06:27] – appledog
+++ functions [2024/10/20 07:45] (current) – appledog
@@ Line 2: / Line 2: @@
 * Today I will do a lesson on functions.
+Note: This lesson might even be skipped, given that pyhang does not require functions.
 == Functions
@@ Line 9: / Line 11: @@
 * How to make a function (see examples below)
-== Code Example
-* Here is an example:
+== Part 1: What's a function? Making functions
+=== Start Code
+Show this to the students. Does it work? What do we need to do?
 <Code:Python>
-def main():
+x = 5
-    x = 5
+y = 3
-    y = 12
-    z = add(x, y)
-    print(z)
-def add(a, b):
+a = add(x, y)
-    c = a + b
+s = sub(x. y)
-    return c
+m = mul(x, y)
+d = div(x, y)
-if __name__ == "__main__":
+print(a, s, m, d)
-    main()
 </Code>
-* There are three parts.
+=== Mid Code
-** One, "def main()" creates the main() function.
+Writing the four functions
-** Two, "def add(a, b)" creates a function with two arguments, or, parameters.
-** Three, "if __name__ == main...." means, to run the "main" function first.
-So you see, you can use the add() function to add numbers.
+=== End Code
+adding idiv(), irem()
-== Homework
-* Classwork/Hommework: Students must:
-** Write a function to multiply two numbers.
-** Write a function to divide two numbers.
-** Write a function to subtract two numbers.
-** Test the program! //(How do you  test? use print() to show the answer.)//
-=== Advanced
+== Part 2: Refactoring a rot13 program
-Is this too easy? Here are some more challenging questions:
+=== Start Code
+We start here, and the journey is to refine the code and learn about functions as we move towards the end code.
-* Write a function that returns a random number.
+<Code:Python>
-* Write a function that returns a random fruit name.
+a = "hello"
-or maybe,
+for c in a:
-* Write a function that prints "even" or "odd" if the number is even or odd.
+    i = ord(c)
+    # upper case
+    if i >= 65 and i <= 90:
+        i = i + 13
+        if i > 90:
+            i = i - 26
+    # lower case
+    if i >= 96 and i <= 122:
+        i = i + 13
+        if i > 122:
+            i = i - 26
+    print(b, end='')
+</Code>
+=== End Code
+<Code:Python>
+def main():
+    a = input("Enter the code: ")
+    while a != "end":
+        print(rot13(a))
+        print("")
+        a = input("Enter the next code: ")
+def rot13(a):
+    r = ""
+    for c in a:
+        r += rot13_letter(c)
+    return r
+def rot13_letter(c):
+    i = ord(c)
+    # capital letters
+    if is_letter(c):
+        i = i + 13
+        if not is_letter(chr(i)):
+            i = i - 26
+    return  chr(i)
+def is_letter(c):
+    i = ord(c)
+    if i >=65 and i <= 90:
+        return True
+    elif i >= 96 and i <= 122:
+        return True
-<Code:Python|Example answer!>
-def isEven(a):
-    x = a // 2      #NOTE: / always returns a float. // always returns the lowest integer!
-    if a == x:
-        return "even"
     else:
-        return "odd"
+        return False
+if __name__ == '__main__':
+    main()
 </Code>
-There are many, many ways to do this. The students should be able to think of at least this:
+== Part 3: 3n+1 example
+Now the students must do things on their own.
-<Code:Python|Example answer 2!>
+=== Start Code
-def isEven(a):
+<Code:Python>
-    while a >= 2:
-        a = a - 2
+n = 10
-    if a == 0:
+while n > 1:
-        print("even")
+    if n % 2 == 0:
+        # Even
+        n = n // 2
     else:
-        print("odd")
+        # Odd
+        n = 3 * n + 1
+        print(str(n))
+if __name__ == '__main__':
+    main()
+</Code>
+=== End Code
+<Code:Python>
+def main():
+    n = input("Please enter a number: ")
+    n = int(n)
+    c = 0
+    print("Start: " + str(n), end = '')
+    while n > 1:
+        print(', ', end = '')
+        c = c + 1
+        if c % 10 == 0:
+            print("")
+        if n % 2 == 0:
+            n = n // 2      # Even
+        else:
+            n = 3 * n + 1   # Odd
+        print(str(n), end = '')
+    print(".")
+    print(f"There were {c} numbers.")
+if __name__ == '__main__':
+    main()
 </Code>
-If this challenge is too easy, they can always write a function that determines if a number is prime.