CSCI 150 HW: Function Stack Tracing

Due: Monday, February 26

To receive full credit, for each exercise you should do the following:

1. Predict: First, complete the exercise without using the Python interpreter. (You are welcome to refer to your notes or textbook, read Python documentation, look at examples from class, etc.; just don’t actually run any code.) Trace the execution of the code in the exercise, including updating variables and any printed output.

2. Check: Run the code. Does the actual output agree with what you wrote down in step 1?

3. Evaluate: If your answer to part 1 was different than the actual output, keep experimenting with it, consult the textbook or Python documentation, ask a friend or TA or professor, etc. until you can explain why the code works the way it does and what your misunderstanding(s) were in part 1. (You do not need to do anything for step 3 if the output agrees exactly with what you wrote in step 1.)

You should consider the code in each exercise separately from the other exercises.

1. Consider the functions defined below. Trace the execution when main1() is called.

    def foo(a: int) -> int:
        b = 3*a + 2
        return b
        print("In foo")
   
    def bar(x: int, y: int) -> int:
        return foo(x) + foo(y)
   
    def main1():
        print(f"The value is {bar(2,3)}")
   
    main1()
   

2. Consider the functions defined below. Trace the execution when main2() is called.

    def f1():
        print("mushroom")
   
    def f2():
        f1()
        print("badger")
        f1()
   
    def f3(n: int):
        f2()
        if n > 5:
            print("snake")
            f1()
        else:
            print("snaaaaake")
   
    def main2():
        f3(2)
        f3(6)
   
    main2()
   

3. Trace the execution when main3 is called.

    def main3():
        s: int = 0
        i: int = 0
        while i < 5:
            j: int = 0
            while j < i:
                s += j
                j += 1
            i += 1
        print(s)
   
    main3()
   

Your solution should be hand-written (or typed) and contain the following:

• For each piece of code, you should turn in a completed trace, including any printed output, which was generated prior to running the code on a machine.
• If your check in step 2 indicated a mistake, correct it, and explain what you got wrong initially and why the code produces the answer it does.

Specifications

• To be considered complete you must work each given problem, and you must have the correct answer (after step 2 if needed), along with correct explanations where appropriate.