Lecture 6 - Exercises

6A - Conditional Statements

1. What does the following program print?

   wwu_founded = 1893
   if (wwu_founded // 1000) < 1:
       wwu_founded = "eighteen ninety three"
   if type(wwu_founded) == type("some text"):
       print("WWU was founded in", wwu_founded)
   else:
       print("Year founded:", wwu_founded)

2. Some of the following expressions could fill in the blank below to make the following program print oolong. Which ones are they?

   if (True and (_______ or not True)) and not False:
       print("green")
   else:
       print("oolong")

   1. True
   2. False
   3. not True
   4. not False
   5. 3 == 4
   6. 17 % 2 == 1

3. Is there anything that could fill in the blank in the program above that would cause the program to print both green and oolong?

6B - Nested and Chained Conditionals

Consider the following program.

# assume x and y are numbers
if x < y:
    print("x is less than y")
else:
    if x > y:
        print("x is greater than y")
    else:
        print("x and y must be equal")

4. How many comparison operators (>, <) are evaluated when the program is run with x set to 4 and y set to 5?
5. How many comparison operators (>, <) are evaluated when the program is run with x set to 8 and y set to 3?
6. Rewrite the program to use chained conditionals (i.e., elif) instead of nested if statements.

Consider the following program:

# Program 0:
if (a < 0) == True:
    print(0)
else:
    if a >= 0:
        print(a)

7. Which of the following programs are equivalent to Program 0? In other words, which of the following has exactly the same output regardless of the value of a? (hint: what values of ‘a’ would you want to check in a test table?)

   # Program 1:
   if a < 0:
       print(0)
   else:
       print(a)
   
   # Program 2:
   if (a < 0) == True:
       print(0)
   print(a)
   
   # Program 3:
   if (a > 0) == True:
       print(a)
   else:
       print(0)
   
   # Program 4:
   if (a < 0) == True:
       print(0)
   if a >= 0:
       print(a)

8. Of the programs above that are equivalent to 0 (including Program 0 itself), which is the simplest and thus most preferable way to write it?

9. Consider the following three programs. Give the smallest positive integer value for the variable num_tacos such that the three programs print exactly the same thing when they are executed. Hint: what values would you put in a testing table?

   Program 1:

   if (num_tacos == 32):
       print("32 tacos")
   elif (num_tacos < 32):
       print("Too few tacos")
   elif (num_tacos == 32):
       print("32 tacos")
   elif (num_tacos % 5 == 0):
       print("Oh yes, tacos!")
   else:
       print("Too many tacos") 

   Program 2:

   if (num_tacos == 32):
       print("32 tacos")
   if (num_tacos < 32):
       print("Too few tacos")
   if (num_tacos == 33):
       print("33 tacos")
   if (num_tacos % 5 == 0):
       print("Oh yes, tacos!")
   else:
       print ("Too many tacos")

   Program 3:

   if (num_tacos == 32):
       print("32 tacos")
   else:
       if (num_tacos < 32):
           print("Too few tacos")
       else:
           if (num_tacos == 34):
             print("34 tacos")
           else:
               if (num_tacos % 5 == 0):
                   print("Oh yes, tacos!")
               else:
                   print ("Too many tacos")