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Teaching Since:	Jul 2017
Last Sign in:	305 Weeks Ago
Questions Answered:	15833
Tutorials Posted:	15827

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MBA,PHD, Juris Doctor
Strayer,Devery,Harvard University
Mar-1995 - Mar-2002

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Manager Planning
WalMart
Mar-2001 - Feb-2009

Category > Computer Science Posted 11 Dec 2017 My Price 10.00

case class Author(penName: String, realName: String)

I have one more question to ask. Thank you so much!

object Amazon {

case class Author(penName: String, realName: String)
case class Publisher(name: String)
case class Book(title: String, author: List[Author], publisher: Publisher, year: Int, price: Double)
case class Series(name: String, books: List[Book])

// Find all books that written by an author
// The authorName should match either pen or real name.
// If there are no books that matches the author, return an empty list
def findAll(books: List[Book], authorName: String): List[Book] = ???

// Find all books that was published on a given year.
// If no books were published that year, you should get an empty list
def findAll(books: List[Book], year: Int): List[Book] = ???

// Find average price of all the books by the author
def findAveragePrice(books: List[Book], author: Author): Double = ???

// Find average price of all the books given a publisher
def findAveragePrice(books: List[Book], publisher: Publisher): Double = ???

// Generalize above two functions into one that finds a average price among books that matches a predicate
def findAverage(books: List[Book], p: Book => Boolean): Double = ???

// Given a list of books, produce a list of unique authors
// You should use .toSet method on List
def authors(books: List[Book], author: Author): Set[Author] = ???

// Given a list of books, produce a list of unique publisher
// You should use .toSet method on List
def publishers(books: List[Book], publisher: Publisher): Set[Publisher] = ???

// Generalize above two functions.
// You should use .toSet method on List
def toSet[A](books: List[Book], p: A => Boolean): Set[A] = ???

// Given a book series, find the total cost of the collection
def total(series: Series): Double = ???

// Given a book series, produce a list of unique authors that contributed
// You should use .toSet method on List
def authors(series: Series): Set[Author] = ???

def main(args: Array[String]): Unit = {
    val huckfinn = Book(
      "The Adventures of Huckleberry Finn",
      List(Author("Mark Twain", "Samuel Langhorne Clemens")),
      Publisher("Chatto & Windus"), 1885, 5.40)

    val design = Book(
      "Design Patterns: Elements of Reusable Object-Oriented Software",
      List(
        Author("Erich Gamma", "Erich Gamma"),
        Author("Richard Helm", "Richard Helm"),
        Author("Ralph Johnson", "Ralph Johnson"),
        Author("John Vlissides", "John Vlissides")
      ), Publisher("Addison-Wesley"), 1994, 28.11)

    val lotr = Series("The Lord of the Rings", List(
      Book(
        "The Followship of the Ring",
        List(Author("J. R. R. Tolkien", "John Ronald Reuel Tolkien")),
        Publisher("George Allen & Unwin"), 1954, 7.99)
    ))

    val amazon = List(huckfinn, design)

    assert(findAll(amazon, "Richard Helm") == List(design))

    assert(total(lotr) == 7.99)

    //You should write more tests
}

}
object Lab12 {

//This is a immutable data structure.
//All the methods should not modify the existing List
trait List[+A] {
    //Returns the (i + 1)th element in the list
    def get(i: Int): A = ???

    //Prepends an element at the beginning of the list
    def prepend[B >: A](a: B): List[B] = Cons(a, this)

    //Appends an element at the end of the list
    def append[B >: A](b: B): List[B] = ???

    //Replaces the head of the list with a
    def setHead[B >: A](a: B): List[B] = ???

    //Removes the last element in the list
    def init: List[A] = ???

    //Removes the first n elements in the list
    def drop(n: Int): List[A] = ???

    //Removes last (length - n) elements in the list
    def take(n: Int): List[A] = ???

    //Appends two lists together
    def append[B >: A](that: List[B]): List[B] = ???

    //Produces B by combining all the elments in the list using the function f starting with z then right most element
    def foldRight[B](z: B)(f: (A, B) => B): B = ???

    //Produces B by combining all the elments in the list using the function f starting with z then left most element
    def foldLeft[B](z: B)(f: (B, A) => B): B = ???

    //returns true if all of the elements in the list returns true for the predicate f
    def forAll(f: A => Boolean): Boolean = ???

    //returns the length of the list
    def length: Int = ???

    //returns a reverse of the list (use foldLeft or foldRight)
    def reverse: List[A] = ???

    //Transform each of the element using f
    def map[B](f: A => B): List[B] = ???

    //Transform each of the element using f then flatten
    def flatMap[B](f: A => List[B]): List[B] = ???

    //returns a new list only containing elements that satisfies the predicate f
    def filter(f: A => Boolean): List[A] = ???
}

object List {
    //Given a list of list, return a flattened list
    // List(List(1,2), List(3,4), 5).flatten == List(1,2,3,4,5)
    def flatten[A](list: List[List[A]]): List[A] = ???

    //Creates a new list of size n filled with element a
    def fill[A](n: Int)(a: A): List[A] = ???

    def apply[A](args: A*): List[A] =
      if (args.isEmpty) Nil
      else Cons(args.head, apply(args.tail: _*))
}

case object Nil extends List[Nothing]

case class Cons[A](head: A, tail: List[A]) extends List[A]

def main(args: Array[String]): Unit = {
    assert(List(1,2,3,4).get(2) == 3)
    assert(List(1,2,3).prepend(0) == List(0,1,2,3))
    assert(List(1,2).append(3) == List(1,2,3))
    assert(List(1,2,3).setHead(0) == List(0,2,3))
    assert(List(1,2,3).init == List(1,2))
    assert(List(1,2,3,4,5).drop(2) == List(3,4,5))
    assert(List(1,2,3,4,5).take(2) == List(1,2))
    assert(List(1,2).append(List(3,4)) == List(1,2,3,4))
    assert(List(1,2,3,4,5).forAll(x => x > 0) == true)
    assert(List(1,2,3,4,5).forAll(x => x < 3) == false)
    assert(List(1,2,3,4).foldRight(0)((a, b) => a + b) == 10)
    assert(List(1,2,3,4).foldLeft(0)((b, a) => b + a) == 10)
    assert(List(1,2,3,4).length == 4)
    assert(List(1,2,3,4).reverse == List(4,3,2,1))
    assert(List.flatten(List(List(1,2), List(3,4))) == List(1,2,3,4))
    assert(List(1,2,3).map(x => x * x) == List(1, 4, 9))
    assert(List(1,2,3).flatMap(x => List(x, x)) == List(1,1,2,2,3,3))
    assert(List(1,2,3,4,5).filter(x => x % 2 == 0) == List(2,4))
    assert(List.fill(3)(1) == List(1,1,1))
}
}

Attachments:

1512990840-lab12.doc

Answers

SophiaPretty

(5)

Status NEW Posted 11 Dec 2017 11:12 AM My Price 10.00

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