HW-Recursion-student-template.scala 2.82 KB
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// Copyright (c) 2020 EPITA Research and Development Laboratory
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without restriction,
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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package homework
import lecture.Recursion._

// Assignment name: Recursion excercise
//
// This homework assignment accompanies section "Recursion".
// The test cases can be found in the file RecursionTestSuite.scala
// You should complete the functions, replacing ??? with correct Scala
// code so that the tests pass.
//
// In the lecture we developed three functions for summing a list of
// integers.  Three different techniques were used.   In this assignment
// you should use similar techniques to create three functions to sum a
// list of Double, and also to find the product of a list of Double.

object Recursion {
  // follow the examples from the lecture to create the following functions
  // sumDoublesBySimpleRecursion()
  // sumDoublesByTailRecursion()
  // sumDoublesByFold()
  //
  // and also
  //
  // productDoublesBySimpleRecursion()
  // productDoublesByTailRecursion()
  // productDoublesByFold()

  def sumDoublesBySimpleRecursion(doubles: List[Double]): Double = {
    doubles match {
      case List() => ???
      case d :: ds => ??? + sumDoublesBySimpleRecursion(???)
    }
  }

  def sumDoublesByTailRecursion(doubles: List[Double]): Double = {
    def sumRest(acc: Double, rest: List[Double]): Double = {
      ???
      }
    }

    sumRest(???, ???)
  }

  def sumDoublesByFold(doubles: List[Double]): Double = {
    doubles.fold(??)(???)

  }


  def productDoublesBySimpleRecursion(doubles: List[Double]): Double = {
    doubles match {
      ???
    }
  }

  def productDoublesByTailRecursion(doubles: List[Double]): Double = {
    def productRest (acc: Double, rest: List[Double] ): Double = {
      ???

    }

    ???
  }

  def productDoublesByFold(doubles: List[Double]): Double = {
    ???
  }

}