Scala forall example?

scala forall option
scala exists
scala forall type
scala foreach
scala filter
scala list
scala map
scala list contains

I tried Google search and could not find a decent forall example. What does it do? Why does it take a boolean function?

Please point me to a reference (except the Scaladoc).

The forall method takes a function p that returns a Boolean. The semantics of forall says: return true if for every x in the collection, p(x) is true.

So:

List(1,2,3).forall(x => x < 3)

means: true if 1, 2, and 3 are less than 3, false otherwise. In this case, it will evaluate to false since it is not the case all elements are less than 3: 3 is not less than 3.

There is a similar method exists that returns true if there is at least one element x in the collection such that p(x) is true.

So:

List(1,2,3).exists(x => x < 3)

means: true if at least one of 1, 2, and 3 is less than 3, false otherwise. In this case, it will evaluate to true since it is the case some element is less than 3: e.g. 1 is less than 3.

Scala List forall() method with example, Scala List forall() method with example. The forall() method is utilized to check if the given predicate satisfies all the elements of the list or not. Return Type: It returns true if the stated predicate holds true for all the elements of the list else it returns false. Scala Iterator forall() method with example The forall() method belongs to the concrete value members of the Class AbstractIterator. It is defined in the class IterableOnceOps. It tests whether a used predicate holds for all the elements of the stated collection.

A quick example of how you can play with this function using a Scala script.

create a myScript.scala file with

println(args.forall(p => (p.equals("a"))))

and call it with

scala myScript.scala a a a  // true
scala myScript.scala a b c  // false

Scala Iterator forall() method with example, Scala Iterator forall() method with example​​ It may not terminate for the infinite sized collection. Return Type : It returns true if the stated collection is empty or if the given predicate p holds for all elements of this collection, else it returns false. Scala forall method is used for testing each element of a collection. It is a predicate operation which returns a boolean value based on some validation performed on each item of the collection. Normal way of validating each item in a collection. The below example is imperative style programming

Scala's forall is also a great tool to do something like applying logical and to a list of boolean values with the early exist:

val evalResults: List[Boolean] = List(evaluateFunc1(), evaluateFunc2(), evaluateFunc3(), evaluateFunc4(), evaluateFunc5())

evalResults.forall(result => result == true)

Scala forall example?, The forall method takes a function p that returns a Boolean. The semantics of forall says: return true if for every x in the collection, p(x) is true. Scala Short !=(x: Long) method with example Scala List forall() method with example The forall() method is utilized to check if the given predicate satisfies all the elements of the list or not.

Scala forall method with examples – StaticReference, Scala forall method with examples. Scala list forall example. Scala forall applies a function to each item of the collection. Scala Seq forall example. object StaticReference { def main(args: Array[String]) { val seq = Seq(1, 2, 3, 4, 5); val ouput = seq.forall(item => { if (item < 10) { true } else false }) } } Scala It is an irrefutable pattern, so effectively it is a full function with pattern parameters. On 3/6/09, Martin S. Weber < martin [dot] weber [at] nist [dot] gov > wrote: remains to be asked, why is it patterns aren't allowed as formal parameters?

Forall, For example, we take an empty Option, all predicates making assertions about its content should return false. The same is valid for Scala  Besides having a bad memory, I haven’t been able to work with Scala much recently, so I’ve been putting together this list of for loop examples.. This page is a work in progress, and as of tonight I haven’t tested some of the examples, but if you’re looking for some Scala for loop examples — technically called a for-comprehension or for-expression — I hope these examples are

Forall semantics - Question, For Example, def foo1(x :(Int,Float)) = x match { case (i, f) => } def foo2  Overview. In this tutorial, we will learn how to use the foldRight function with examples on collection data structures in Scala.The foldRight function is applicable to both Scala's Mutable and Immutable collection data structures.

Comments
  • scala-lang.org/api/current/scala/collection/immutable/List.html: Tests whether a predicate holds for all elements of this list.
  • maybe you got confused because you thought of the functionality of foreach instead (iterate through all elements)
  • Yes I was thinking its a parallel version of foreach.
  • so forall(foo) is equivalent to foldLeft(true)((x,y)=> x & foo(y))
  • @Jus12, yes, with the correction that it uses && because it does short-circuit evaluation (it stops evaluating foo if it finds a false).
  • why not use the REPL?