Question

Problem 8 In class, we discussed the difference between a pure (or effect-free) function (i.e. one that returns a value, but does not produce an effect) and a mutating function i.e one that changes the value of its parameters). In this exercise, we ask you to demonstrate your understanding o this distinction by implementing the same functionality as both a pure function, and as a mutating function. Both functions take a list of int as a parameter. The pure variant will return a new list containing the integers in reversed order. The mutating variant will retur None, and will instead modify the list that it's given Your functions should have these signatures: def reverse pure (xs) signature: list(int)> list(int) Returns a list of integers in reverse order pass def reverse ut (x) signature: list(int) > NoneType Reverses the list of integers in place pass When implementing reverse nut, consider carefully how one can reverse the items in a list without creating a new list A contrasting example: >> mylist [5, 12, 34, 0. 11 # The list of numbers >>> newlist - reverse-pure (aylist) # Call the pure function >> print(nevlist) 1, 0, 34, 12, 5] >> print (ylist) [5, 12, 34, 0, 11 >> reverse aut (nylist) >> print (ylist) 1, 0, 34, 12, 5] # The new , revers ed list # The original list is unchanged # Call the mutating function (returns None) # Original list is reversed in-place For this problem, you may not use the built-in Python functions for reversing list, reverse and reversed. You should implement the function using a loop.

Answer 1

Here is the completed code for this problem. Comments are included, go through it, learn how things work and let me know if you have any doubts or if you need anything to change. Make sure that you maintain proper indentations while pasting the below code into your program, I’m also attaching the code in both text and image formats, so in case if the indentation is messed up, you can refer the image and maintain proper spacing in each and every line. Thanks

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#code

def reverse_pure(lst):
    #defining an empty list
    reversed=[]
    #finding last index of parameter list
    index=len(lst)-1
    #iterating from rear to front
    while index>=0:
        #adding current element to new list
        reversed.append(lst[index])
        index-=1 #previous index
    return reversed #returning new list containing elements in reverse order

def reverse_mut(lst):
    #finding the length of lst list
    size=len(lst)
    #looping from i=0 to i=size/2
    for i in range(size//2):
        #swapping elements at index i and index size-i-i
        #that is swapping ith element from front and ith element from rear
        temp=lst[i]
        lst[i]=lst[size-1-i]
        lst[size - 1 - i]=temp
    #end of method, now the lst will be in reverse order.
   
#testing
myList=[5,12,34,0,1]
newList=reverse_pure(myList)
print(newList) # [1, 0, 34, 12, 5]
print(myList) # [5, 12, 34, 0, 1]
reverse_mut(myList)
print(myList) # [1, 0, 34, 12, 5]

#code screenshot

null

#output

[1, 0, 34, 12, 5]

[5, 12, 34, 0, 1]

[1, 0, 34, 12, 5]