Getting Started
Download lab17.scala into any directory. Change directory to that directory. Run the program using the command
scala lab17.scala
Functional Programming Exercises
In this lab, you will gain some more experience with functional programming in Scala by completing the definitions of a series of methods.
As you work on each function, you can remove the line of code that reads
throw new RuntimeException("TODO")
There are tests in the main function of the Lab17 class. You can uncomment each test as you complete each function.
General hints
- think about a base case for each recursive function
- you can use list.head to get the first element of a list and list.tail to get a list containing the remaining elements of a list (after the first)
- use element :: list to construct a new list by prepending element to list
Task 1
Complete the definition of the allEven function, which takes a list of integers and returns true if all of the elements are even, false otherwise.
Task 2
Complete the definition of the reverse function, which takes a list of integers and returns a list with the elements of the original list reversed.
This function has a nested helper function reverseWork, which is the part you will need to implement. This function should be tail-recursive: the accum parameter is used to build up the partial results of the computation.
Task 3
Complete the definition of the makeIntList function, which takes an integer n and returns a list containing all of the integers from 1 to n, inclusive.
This function has a nested helper function makeIntListWork, which is the part you need to implement.
Task 4
Complete the definition of the replaceMultiplesOf function, which takes a list of integers and an integer n, and returns a list in which each element of the original list that is both
- greater than n
- an exact multiple of n
is replaced by 0.
This function has a nested helper function replaceMultiplesOfWork, which is the part you need to implement.
Task 5
Complete the definition of the allPrimesLessThan function, which takes an integer n and returns a list of all of the prime numbers less than n.
The idea is that you can repeatedly call replaceMultiplesOf to change the multiples of 2, 3, 4, etc. to 0. After all such multiples have been replaced, filter the list to remove all of the 0 elements.
