Solutions: You can find the file with solutions for all questions here.

## Lambdas

### Question 1: Make your own lambdas

For each of the following expressions, write functions `f1`, `f2`, `f3`, and `f4` such that the evaluation of each expression succeeds, without causing an error. Be sure to use lambdas in your function definition instead of nested `def` statements. Each function should have a one line solution.

``````def f1():
"""
>>> f1()
3
"""
return 3

def f2():
"""
>>> f2()()
3
"""
return lambda: 3

def f3():
"""
>>> f3()(3)
3
"""
return lambda x: x

def f4():
"""
>>> f4()()(3)()
3
"""
return lambda: lambda x: lambda: x``````

Use OK to test your code:

``````python3 ok -q f1
python3 ok -q f2
python3 ok -q f3
python3 ok -q f4``````

### Question 2: Higher Order Lambdas

Return a lambda function that takes in a multiplier and returns a lambda function that given an input will return the input multiplied by the multiplier.

``````def higher_order_lambdas():
"""
Return a lambda function that takes in a multiplier and returns a lambda function that given an input will
return the input multiplied by the multiplier
>>> hol = higher_order_lambdas()
>>> doubles = hol(2)
>>> doubles(3)
6
>>> hol = higher_order_lambdas()
>>> triples = hol(3)
>>> triples(4)
12
"""
return lambda m : lambda n : m * n``````

Use OK to test your code:

``python3 ok -q higher_order_lambdas``

### Question 3: Lambdas and Currying

We can transform multiple-argument functions into a chain of single-argument, higher order functions by taking advantage of lambda expressions. This is useful when dealing with functions that take only single-argument functions. We will see some examples of these later on.

Write a function `lambda_curry2` that will curry any two argument function using lambdas. See the doctest if you're not sure what this means.

``````def lambda_curry2(fn):
"""
Returns a Curried version of a two argument function func.
>>> y = x(3)
>>> y(5)
8
"""
return lambda arg1: lambda arg2: fn(arg1, arg2)``````

Use OK to test your code:

``python3 ok -q lambda_curry2``

## Dictionaries

### Question 4: Replace All

Given a dictionary `d`, return a new dictionary where all occurences of `x` as a value (not a key) is replaced with `y`.

``````def replace_all(d, x, y):
"""
>>> d = {'foo': 2, 'bar': 3, 'garply': 3, 'xyzzy': 99}
>>> e = replace_all(d, 3, 'poof')
>>> e == {'foo': 2, 'bar': 'poof', 'garply': 'poof', 'xyzzy': 99}
True
"""
new = {}
for key in d:
if d[key] == x:
new[key] = y
else:
new[key] = d[key]
return new``````

Use OK to test your code:

``python3 ok -q replace_all``

### Question 5: Merge Dictionaries

Implement the function `merge_dict`. The `merge_dict` function merges two dictionaries with the same keys together.

``````def merge_dict(d1, d2):
"""Returns a dictionary with two dictionaries merged together. You can assume that the same keys appear in both dictionaries.
>>> data8 = {"midterms":1, "projects":3}
>>> data100 = {"midterms":2, "projects":3}
>>> combined_exams = merge_dict(data8, data100)
>>> combined_exams
{'midterms': 3, 'projects': 6}
>>> sunday_orders = {"pizza": 3, "hot dogs": 2, "fries": 5}
>>> monday_orders = {"pizza": 1, "hot dogs": 1, "fries": 8}
>>> combined_orders = merge_dict(sunday_orders, monday_orders)
>>> combined_orders
{'pizza': 4, 'hot dogs': 3, 'fries': 13}
"""
result_dict = {}
for work in d1:
result_dict[work] = d1[work] + d2[work]
return result_dict``````

Use OK to test your code:

``python3 ok -q merge_dict``

## Submit

Make sure to submit this assignment by running:

``python3 ok --submit``