Initial commit of files supporting mutual recursion and tail recursion discussion

MutualRecursion.py

+def parse(expression):      # This should have real logic
+    left_expression = "1"
+    operator = "+"
+    right_expression = "2"
+    return left_expression, operator, right_expression
+
+
+def add(left_expression, right_expression):
+    return evaluate(left_expression) + evaluate(right_expression)
+
+
+def subtract(left_expression, right_expression):
+    return evaluate(left_expression) - evaluate(right_expression)
+
+
+def multiply(left_expression, right_expression):
+    return evaluate(left_expression) * evaluate(right_expression)
+
+
+def divide(left_expression, right_expression):
+    return evaluate(left_expression) / evaluate(right_expression)
+
+
+operator_map = {
+    "+": add,
+    "-": subtract,
+    "*": multiply,
+    "/": divide
+}
+
+
+def evaluate(expression):
+    if expression.isnumeric():
+        return expression
+    else:
+        left_expression, operator, right_expression = parse(expression)
+        return operator_map[operator](left_expression, right_expression)
+
+
+if __name__ == '__main__':
+    print(evaluate("1+2"))

StackBuster.py

+def non_terminating_recursion(a_string, instance_number):
+    a_longer_string = "{} {}".format(a_string, a_string)
+    # print( "Activation instance: {:d}".format(instance_number))
+    return non_terminating_recursion(a_longer_string, instance_number + 1)
+
+
+if __name__ == '__main__':
+    print(non_terminating_recursion("This is a long string that's going to become even longer.", 0))

TailRecursion.py

+def poorly_defined_iterator(a_list):
+    if len(a_list) > 0:
+        print(a_list[0])
+        poorly_defined_iterator(a_list[1:])
+
+
+def slightly_better_iterator(a_list):
+    for item in a_list:
+        print(item)
+
+
+def poorly_defined_adder(a_list):
+    if len(a_list == 0):
+        return 0
+    else:
+        return a_list[0] + poorly_defined_adder(a_list[1:])
+
+
+def slightly_better_adder(a_list):
+    total = 0
+    for item in a_list:
+        total += item
+    return total
+
+
+if __name__ == '__main__':
+    poorly_defined_iterator([1, 2, 3, 4, 5])
+    slightly_better_iterator([1, 2, 3, 4, 5])
+    print(poorly_defined_adder([1, 2, 3, 4, 5]))
+    print(slightly_better_adder([1, 2, 3, 4, 5]))