## Scala forall example?

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?