Every

sealed abstract class Every[+T] extends PartialFunction[Int, T] with Product with Serializable

An ordered, immutable, non-empty collection of elements.

Class Every has two and only two subtypes: One and Many. A One contains exactly one element. A Many contains two or more elements. Thus no way exists for an Every to contain zero elements.

== Constructing Everys ==

You can construct an Every by passing one or more elements to the Every.apply factory method:

Every(1)
Every(1, 2)
Every(1, 2, 3)

Alternatively you can pass one element to the One.apply factory method, or two or more elements to Many.apply:

One(1)
Many(1, 3)
Many(1, 2, 3)

== Working with Everys ==

Every does not extend Scala's Seq or Traversable traits because these require that implementations may be empty. For example, if you invoke tail on a Seq that contains just one element, you'll get an empty Seq:

scala> List(1).tail
res6: List[Int] = List()

On the other hand, many useful methods exist on Seq that when invoked on a non-empty Seq are guaranteed to not result in an empty Seq. For convenience, Every defines a method corresponding to every such Seq method. Here are some examples:

Many(1, 2, 3).map(_ + 1)                  // Result: Many(2, 3, 4)
One(1).map(_ + 1)                         // Result: One(2)
Every(1, 2, 3).containsSlice(Every(2, 3)) // Result: true
Every(1, 2, 3).containsSlice(Every(3, 4)) // Result: false
Every(-1, -2, 3, 4, 5).minBy(_.abs)       // Result: -1

Every does not currently define any methods corresponding to Seq methods that could result in an empty Seq. However, an implicit converison from Every to collection.immutable.IndexedSeq is defined in the Every companion object that will be applied if you attempt to call one of the missing methods. As a result, you can invoke filter on an Every, even though filter could result in an empty sequence—but the result type will be collection.immutable.IndexedSeq instead of Every:

Every(1, 2, 3).filter(_ < 10) // Result: Vector(1, 2, 3)
Every(1, 2, 3).filter(_ > 10) // Result: Vector()

You can use Everys in for expressions. The result will be an Every unless you use a filter (an if clause). Because filters are desugared to invocations of filter, the result type will switch to a collection.immutable.IndexedSeq at that point. Here are some examples:

scala> import org.scalactic._
import org.scalactic._

scala> for (i <- Every(1, 2, 3)) yield i + 1
res0: org.scalactic.Every[Int] = Many(2, 3, 4)

scala> for (i <- Every(1, 2, 3) if i < 10) yield i + 1
res1: scala.collection.immutable.IndexedSeq[Int] = Vector(2, 3, 4)

scala> for {
    |   i <- Every(1, 2, 3)
    |   j <- Every('a', 'b', 'c')
    | } yield (i, j)
res3: org.scalactic.Every[(Int, Char)] =
       Many((1,a), (1,b), (1,c), (2,a), (2,b), (2,c), (3,a), (3,b), (3,c))

scala> for {
    |   i <- Every(1, 2, 3) if i < 10
    |   j <- Every('a', 'b', 'c')
    | } yield (i, j)
res6: scala.collection.immutable.IndexedSeq[(Int, Char)] =
       Vector((1,a), (1,b), (1,c), (2,a), (2,b), (2,c), (3,a), (3,b), (3,c))

== Motivation for Everys ==

Although Every is a general-purpose, non-empty ordered collection, it was motivated by the desire to enable easy accumulation of errors in Ors. For examples of Every used in that use case, see the Accumulating errors with Or section in the main documentation for Or.

Type parameters:

T: the type of elements contained in this Every

Companion:

object

Source:

Every

Value members

Abstract methods

Concrete methods

Deprecated methods

Inherited methods

`Inherited methods`