Lecture-1-2-Recursion.scala 1.96 KB
 Jim Newton committed May 13, 2020 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 ``````// 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, // including without limitation the rights to use, copy, modify, merge, // publish, distribute, sublicense, and/or sell copies of the Software, // and to permit persons to whom the Software is furnished to do so, // subject to the following conditions: // // The above copyright notice and this permission notice shall be // included in all copies or substantial portions of the Software. // // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. package lecture object Recursion { def sumIntegersBySimpleRecursion(ints: List[Int]): Int = { ints match { case List() => 0 // common variable names are also h::t or head::tail or first::rest case i :: is => i + sumIntegersBySimpleRecursion(is) } } def sumIntegersByTailRecursion(ints: List[Int]): Int = { def sumRest(acc: Int, rest: List[Int]): Int = { rest match { case List() => acc case i :: is => sumRest(acc + i, is) } } sumRest(0, ints) } def sumIntegersByFold(ints: List[Int]): Int = { ints.fold(0)(_ + _) } def genLongList(len:Int, value:Double):List[Double] = { List.tabulate(len)(_ => value) } def main(argv:Array[String]):Unit = { val longList = List.tabulate(5673)(n => 0) println(s"sum = \${sumIntegersBySimpleRecursion(longList)}") } }``````