o

scala

PartialFunction 

Companion trait PartialFunction

object PartialFunction

A few handy operations which leverage the extra bit of information available in partial functions. Examples:

```import PartialFunction._

def strangeConditional(other: Any): Boolean = cond(other) {
case x: String if x == "abc" || x == "def"  => true
case x: Int => true
}
def onlyInt(v: Any): Option[Int] = condOpt(v) { case x: Int => x }```
Source
PartialFunction.scala
Since

2.8

Linear Supertypes
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Inherited
1. PartialFunction
2. AnyRef
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Visibility
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Value Members

1. final def !=(arg0: Any)

Test two objects for inequality.

Test two objects for inequality.

returns

`true` if !(this == that), false otherwise.

Definition Classes
AnyRef → Any
2. final def ##(): Int

Equivalent to `x.hashCode` except for boxed numeric types and `null`.

Equivalent to `x.hashCode` except for boxed numeric types and `null`. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For `null` returns a hashcode where `null.hashCode` throws a `NullPointerException`.

returns

a hash value consistent with ==

Definition Classes
AnyRef → Any
3. final def ==(arg0: Any)

The expression `x == that` is equivalent to `if (x eq null) that eq null else x.equals(that)`.

The expression `x == that` is equivalent to `if (x eq null) that eq null else x.equals(that)`.

returns

`true` if the receiver object is equivalent to the argument; `false` otherwise.

Definition Classes
AnyRef → Any
4. final def asInstanceOf[T0]: T0

Cast the receiver object to be of type `T0`.

Cast the receiver object to be of type `T0`.

Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression `1.asInstanceOf[String]` will throw a `ClassCastException` at runtime, while the expression `List(1).asInstanceOf[List[String]]` will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.

returns

Definition Classes
Any
Exceptions thrown

`ClassCastException` if the receiver object is not an instance of the erasure of type `T0`.

5. def clone()

Create a copy of the receiver object.

Create a copy of the receiver object.

The default implementation of the `clone` method is platform dependent.

returns

a copy of the receiver object.

Attributes
protected[lang]
Definition Classes
AnyRef
Annotations
( ... ) ()
Note

not specified by SLS as a member of AnyRef

6. def cond[T](x: T)(pf: PartialFunction[T, Boolean])

Creates a Boolean test based on a value and a partial function.

Creates a Boolean test based on a value and a partial function. It behaves like a 'match' statement with an implied 'case _ => false' following the supplied cases.

x

the value to test

pf

the partial function

returns

true, iff `x` is in the domain of `pf` and `pf(x) == true`.

7. def condOpt[T, U](x: T)(pf: PartialFunction[T, U]): Option[U]

Transforms a PartialFunction[T, U] `pf` into Function1[T, Option[U]] `f` whose result is `Some(x)` if the argument is in `pf`'s domain and `None` otherwise, and applies it to the value `x`.

Transforms a PartialFunction[T, U] `pf` into Function1[T, Option[U]] `f` whose result is `Some(x)` if the argument is in `pf`'s domain and `None` otherwise, and applies it to the value `x`. In effect, it is a `match` statement which wraps all case results in `Some(_)` and adds `case _ => None` to the end.

x

the value to test

pf

the PartialFunction[T, U]

returns

`Some(pf(x))` if `pf isDefinedAt x`, `None` otherwise.

8. def empty[A, B]: PartialFunction[A, B]

The partial function with empty domain.

The partial function with empty domain. Any attempt to invoke empty partial function leads to throwing scala.MatchError exception.

Since

2.10

9. final def eq(arg0: AnyRef)

Tests whether the argument (`that`) is a reference to the receiver object (`this`).

Tests whether the argument (`that`) is a reference to the receiver object (`this`).

The `eq` method implements an equivalence relation on non-null instances of `AnyRef`, and has three additional properties:

• It is consistent: for any non-null instances `x` and `y` of type `AnyRef`, multiple invocations of `x.eq(y)` consistently returns `true` or consistently returns `false`.
• For any non-null instance `x` of type `AnyRef`, `x.eq(null)` and `null.eq(x)` returns `false`.
• `null.eq(null)` returns `true`.

When overriding the `equals` or `hashCode` methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (`o1 eq o2`), they should be equal to each other (`o1 == o2`) and they should hash to the same value (`o1.hashCode == o2.hashCode`).

returns

`true` if the argument is a reference to the receiver object; `false` otherwise.

Definition Classes
AnyRef
10. def equals(arg0: Any)

The equality method for reference types.

The equality method for reference types. Default implementation delegates to `eq`.

See also `equals` in scala.Any.

returns

`true` if the receiver object is equivalent to the argument; `false` otherwise.

Definition Classes
AnyRef → Any
11. def finalize(): Unit

Called by the garbage collector on the receiver object when there are no more references to the object.

Called by the garbage collector on the receiver object when there are no more references to the object.

The details of when and if the `finalize` method is invoked, as well as the interaction between `finalize` and non-local returns and exceptions, are all platform dependent.

Attributes
protected[lang]
Definition Classes
AnyRef
Annotations
( classOf[java.lang.Throwable] )
Note

not specified by SLS as a member of AnyRef

12. final def getClass(): Class[_]

Returns the runtime class representation of the object.

Returns the runtime class representation of the object.

returns

a class object corresponding to the runtime type of the receiver.

Definition Classes
AnyRef → Any
Annotations
()
13. def hashCode(): Int

The hashCode method for reference types.

The hashCode method for reference types. See hashCode in scala.Any.

returns

the hash code value for this object.

Definition Classes
AnyRef → Any
Annotations
()
14. final def isInstanceOf[T0]

Test whether the dynamic type of the receiver object is `T0`.

Test whether the dynamic type of the receiver object is `T0`.

Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression `1.isInstanceOf[String]` will return `false`, while the expression `List(1).isInstanceOf[List[String]]` will return `true`. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.

returns

`true` if the receiver object is an instance of erasure of type `T0`; `false` otherwise.

Definition Classes
Any
15. final def ne(arg0: AnyRef)

Equivalent to `!(this eq that)`.

Equivalent to `!(this eq that)`.

returns

`true` if the argument is not a reference to the receiver object; `false` otherwise.

Definition Classes
AnyRef
16. final def notify(): Unit

Wakes up a single thread that is waiting on the receiver object's monitor.

Wakes up a single thread that is waiting on the receiver object's monitor.

Definition Classes
AnyRef
Annotations
()
Note

not specified by SLS as a member of AnyRef

17. final def notifyAll(): Unit

Wakes up all threads that are waiting on the receiver object's monitor.

Wakes up all threads that are waiting on the receiver object's monitor.

Definition Classes
AnyRef
Annotations
()
Note

not specified by SLS as a member of AnyRef

18. final def synchronized[T0](arg0: ⇒ T0): T0
Definition Classes
AnyRef
19. def toString(): String

Creates a String representation of this object.

Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.

returns

a String representation of the object.

Definition Classes
AnyRef → Any
20. final def wait(): Unit
Definition Classes
AnyRef
Annotations
( ... )
21. final def wait(arg0: Long, arg1: Int): Unit
Definition Classes
AnyRef
Annotations
( ... )
22. final def wait(arg0: Long): Unit
Definition Classes
AnyRef
Annotations
( ... ) ()

Deprecated Value Members

1. def apply[A, B](f: (A) ⇒ B): PartialFunction[A, B]

Converts ordinary function to partial one

Converts ordinary function to partial one

Annotations
Deprecated

(Since version 2.12.5) For converting an ordinary function f to a partial function pf, use `val pf: PartialFunction[A, B] = { case x => f(x) }`. For creating a new PartialFunction, use an explicit type annotation instead, like in `val pf: PartialFunction[Int, String] = { case 1 => "one" }`.

Since

2.10