Lab 6 - Nonlocal, Mutability

Write 2 easy mutating functions.

Instructions: https://inst.eecs.berkeley.edu/~cs61a/su19/lab/lab06/

Solution: https://github.com/tomthestrom/cs61a/blob/master/lab/lab06/lab06.py

Q1: Make Adder Increasing

Write a function which takes in an integer n and returns a one-argument function. This function should take in some value x and return n + x the first time it is called, similar to make_adder. The second time it is called, however, it should return n + x + 1, then n + x + 2 the third time, and so on

def make_adder_inc(n):
    """
    >>> adder1 = make_adder_inc(5)
    >>> adder2 = make_adder_inc(6)
    >>> adder1(2) 
    7
    >>> adder1(2) # 5 + 2 + 1
    8
    >>> adder1(10) # 5 + 10 + 2
    17
    >>> [adder1(x) for x in [1, 2, 3]]
    [9, 11, 13]
    >>> adder2(5)
    11
    """
    "*** YOUR CODE HERE ***"

Q1: Solution

def make_adder_inc(n):
    """
    >>> adder1 = make_adder_inc(5)
    >>> adder2 = make_adder_inc(6)
    >>> adder1(2) 
    7
    >>> adder1(2) # 5 + 2 + 1
    8
    >>> adder1(10) # 5 + 10 + 2
    17
    >>> [adder1(x) for x in [1, 2, 3]]
    [9, 11, 13]
    >>> adder2(5)
    11
    """
    "*** YOUR CODE HERE ***"
    i = 0
    def adder_inc(x):
        nonlocal i
        
        added_sum = n + x + i
        i = i + 1
        return added_sum
    return adder_inc

Q2: Map

Write a function that takes a function and a list as inputs and maps the function on the given list - that is, it applies the function to every element of the list.

Be sure to mutate the original list. This function should not return anything.

def map(fn, lst):
    """Maps fn onto lst using mutation.
    >>> original_list = [5, -1, 2, 0]
    >>> map(lambda x: x * x, original_list)
    >>> original_list
    [25, 1, 4, 0]
    """
    "*** YOUR CODE HERE ***"

Q2: Solution

def map(fn, lst):
    """Maps fn onto lst using mutation.
    >>> original_list = [5, -1, 2, 0]
    >>> map(lambda x: x * x, original_list)
    >>> original_list
    [25, 1, 4, 0]
    """
    "*** YOUR CODE HERE ***"
    for i in range (len(lst)):
        lst[i] = fn(lst[i])