# Tutorial 4 - Problem 5

1. variable1 = 1
2. variable2 = 2

3. def function1():
4.    variable3 = 3
5.    variable4 = variable3
6.    return variable4

7. def function2(parameter1):
8.    variable5 = parameter1 
9.    variable6 = 6
10.   return variable5
    
11. def function3(parameter2, parameter3):
12.    variable7 = parameter2 
13.    variable8 = parameter3
14.    return variable9

# main
15. variable10 = function2(variable3)
16. print(function3(variable5, variable2))
17. variable1 = function1()


# a. What is wrong with it?
# NameError: name 'variable3' is not defined in statement variable10 = function2(variable3)
# NameError: name 'variable5' is not defined in statement print(function3(variable5, variable2))
# NameError: name 'variable9' is not defined in statement return variable9 in function3()

# b. In general, what is the scope of a variable?
# The section of the program over which the variable is known and can be used.

# c. In general, what is the scope of a parameter?
# A parameter is a variable, so its scope, usually, is over the body of the function for which it is a parameter.

# d. In general, what is the relationship between variable scope and the stack frame of a function?
# Variables local to a function (and parameters) are given memory location in the stack frame
# assigned to a fucntion when it is executed. 
# When the execution flow returns from the function to the "caller" of the function, the stack frame
# is recycled, i.e., the variables are no longer accessible, they do no have "scope" anymore.

# e. What is the scope of each of the 10 variables in the Python program?
# Scope of variable1 and variable2 is the whole program.
# Scope of variable3 is lines 4., 5. and 6.
# Scope of variable4 is lines 5. and 6.

# Scope of variable5 is lines 8., 9. and 10.
# Scope of variable6 is lines 9. and 10.

# Scope of variable7 is lines 12., 13. and 14.
# Scope of variable8 is lines 13. and 14.

# Variable9 is problematic (not yet defined) and has no scope.
# Scope of variable10 is lines 15., 16. and 17.

# f. What is the scope of each of the 3 parameters in the Python program?
# Scope of parameter1 is the body of function2, i.e., parameter1 is known over the whole body of function2.
# SCope of parameter2 and parameter3 is the body of function3, i.e., parameter2
# and parameter3 are known over the whole body of function3.