HW5: Scala 1

HW5: Scala 1
 Points 25 Submitting a file upload
Throughout this class, you are not allowed to use loops or mutable variables in Scala. If you
want to use a feature or function we haven't discussed in class, please ask me first.
1. (5 points) Write a function is_prime that takes in an integer x and returns true if x is prime and
false if it is not. To do this, you may write a helper “loop” recursive function that takes one
parameter. You are welcome to create additional non-recursive helper functions. Please define
all helper functions inside is_prime.
2. (5 points) Consider the function add_third
def add_third(x:Int):Int = {
if(x<1) 0
else x+add_third(x-3)
 }
You will write a more general version of this function, add_fth, where instead of recursing on x-3, we
will use a function f to find the value we will recurse with. To help you get started, here are a couple
of questions to answer (you don’t need to turn in the answers, just write the function)
Step 1: add_fth will take two parameters, a function f, and an Int x. What should the type of f be?
Step 2: How will we use f in the body of the function?
In addition to the function add_fth, include a function call to add_fth that will have the same behavior
as a function call to add_third. To do this you must first define a function to pass as a parameter to
add_fth.
3. (10 points) Write a more general version of the sum_f and combine functions from class called
apply_combine that applies a function f(taken as a parameter) to the integers from 1 to x(taken as
a parameter), then combines those values using another function g(taken as a parameter). So
apply_combine takes in three parameters: a function f that takes in an Int and returns an Int; a
function g that takes in two Ints and returns an Int; and an Int x . It then returns the result of using
the function g to combine the values gained by applying f to 1, 2, …, x. For example, if I define
def add(x:Int, y:Int) :Int = x+y
def square(x:Int):Int = x*x
4/3/23, 7:47 PM HW5: Scala 1
https://camino.instructure.com/courses/87658/assignments/619987?module_item_id=1469336 2/2
then
apply_combine(square, add, 4)
would return 30=16+9+4+1
And if I define
def mult(x:Int, y:Int) :Int = x*y
 def identity(x:Int) = x
then
apply_combine(identity, mult, 4)
would return 24
4. (5 points) Read the blog post here: https://www.smashingmagazine.com/2014/07/dont-bescared-of-functional-programming/ (https://www.smashingmagazine.com/2014/07/dont-be-scared-offunctional-programming/)
(you only need to read up to “Let’s Get Real”)
Write a 100-150 word summary of this article; you don’t have to rehash the whole running example,
but please provide at least three ideas that you found interesting in the article. This article uses
javascript; you should be able to follow it without any javascript background (one helpful tip:
something that looks like this:
function(item) {
 return item[propertyName];
 }
Is defining an anonymous function.)
Please upload the first three problems as part of the same file. Please name it
HW5Yourlastname.scala (or save and submit as a .txt if that's easier to submit) where Yourlastname
is your last name. Name the file for problem 4 HW5P4Yourlastname.pdf (or .txt)