Foldleft in scala example
WebfoldLeft applies a two-parameter function op to an initial value z and all elements of this collection, going left to right. Shown below is an example of its usage. Starting with an initial value of 0, foldLeft here applies the function (m, n) => m + n to each element in the List and the previous accumulated value. WebJul 10, 2009 · Here are a few more examples. list.foldLeft(0)((b,a) => b+a) list.foldLeft(1)((b,a) => b*a) list.foldLeft(List[Int]())((b,a) => a :: b) The first line is super simple. It’s almost like the example I described above, but the z value is the number 0 instead of string “X”.
Foldleft in scala example
Did you know?
WebUsage Below is an example program of showing how to use foldRight method − Example object Demo { def main(args: Array[String]) = { val list = List(1, 2, 3 ,4) //apply operation to get sum of all elements of the list val result = list.foldRight(0) (_ + _) //print result println(result) } }
WebHowever, unlike foldLeft() and foldRight(), the initial value given to fold() can only be of the same type or a supertype of the type of the collection. In this example the order is not relevant, so you can change fold() to foldLeft() or foldRight() and the result will remain the same. Using a function that is sensitive to order will alter results. WebMar 22, 2024 · Here’s an example of using the foldRight function in Scala: val numbers = List (1, 2, 3, 4, 5) val reversedNumbers = numbers.foldRight (List [Int] ()) ( (num, acc) => acc :+ num) println (reversedNumbers) // Output: List (5, 4, 3, 2, 1) In this example, we have a list of numbers. We want to reverse the order of the list using foldRight.
http://allaboutscala.com/tutorials/chapter-8-beginner-tutorial-using-scala-collection-functions/scala-scanleft-example/ WebFeb 17, 2024 · As a brief note, here’s some Scala source code that shows how to write a fold left ( foldLeft) function using recursion: // scala 2 object FoldLeft extends App { val a = List (1,2,3,4) def add (a: Int, b: Int) = a + b println (foldLeft (0) (a) (add)) def foldLeft (lastResult: Int) (list: List [Int]) (f: (Int, Int) => Int): Int = list match ...
WebNov 22, 2024 · The reduceLeft function is applicable to both Scala's Mutable and Immutable collection data structures. The reduceLeft method takes an associative binary operator function as parameter and will use it to collapse elements from the collection.
WebAug 28, 2024 · Scala fold/reduce FAQ: Can you share an example that shows how to get the max or min value from a collection using the Scala reduceLeft collections method?. A Scala reduceLeft example. I don't have much time today, but sure, here’s a quick Scala reduceLeft example. The following code will determine which student has the max … book orphans of the empireWebJul 1, 2024 · Although you can foldLeft a list to find the minimum, Scala has a built in function for this: List(3, 2, 1).min() To show the usefulness of foldLeft, let’s look at something that is not as easy. book or recordWebJul 26, 2024 · Example #1: object GfG { def main (args:Array [String]) { val m1 = Map (3 -> "geeks", 1 -> "for", 2 -> "cs") val result = m1.foldLeft (0) (_+_._1) println (result) } } 6 Here, zero in the foldLeft method is the initial value. Example #2: object GfG { def main (args:Array [String]) { val m1 = Map (3 -> "geeks", 1 -> "for", 1 -> "for") book or movie firstWebNov 25, 2024 · In our first example we were folding on a type List [Int] and had a start type of Int. Int is a supertype of List [Int]. The second constraint of fold is that the start value must be neutral, i.e. it must not change the result. For example, the neutral value for an addition operation would be 0, 1 for multiplication, Nil lists, etc. book orphan trainWebAug 28, 2024 · The foldLeft method, found on Scala sequences, is a fun little method. Its signature looks like this: def foldLeft [B] (z: B) (f: (B, A) => B): B What that signature means is that foldLeft is a method that takes … godwin coachesWebDec 19, 2024 · //fold example val listRdd = spark. sparkContext. parallelize ( List (1,2,3,4,5,3,2)) println ("Partitions : "+ listRdd. getNumPartitions) println ("Total : "+ listRdd. fold (0)(( acc, ele) => { acc + ele })) println ("Total … godwin coat of armsWebHowever, sometimes you may need to add multiple columns after applying some transformations n that case you can use either map () or foldLeft (). Let’s see an example with a map. I don’t have a real-time scenario to add multiple columns, below is just a skeleton on how to use. I will update this once I have a Scala example. godwin construction