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Questions tagged [partialfunction]

Questions about the Scala's PartialFunction type. For questions about the broader concept of partial functions (i.e. functions not defined for all of their inputs), use [partial-functions]. For questions about partially applied functions, use [partial-application].

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Adding new arguments to a partial function

Is there some simple way how to add new arguments to a partial function, so that resulting function is defined in the same domain as before (new arguments have no influence on its partiality)? Following code works, but seems a bit verbose. val…
Suma
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How to partially apply case class with type parameter in Scala

So I have a tuple that I want to pass as the parameters for a case class in Scala. For case classes without type parameters, this is easy, as I can do: scala> case class Foo(a: Int, b: Int) defined class Foo scala> (Foo.apply _) res0: (Int,…
cdmckay
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How to avoid explicit .isDefinedAt() call in pattern matching guard

I have some Akka-based actor system where multiple kind of actors is based on same template due to a fact that those actors only differ by a type of response value. For example: final case class Request(data: Any) final case class Response(data:…
Seigert
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Partial Function pattern match split into a class and a trait

Lift uses a PartialFunction on their implementation of Comet Actors, and you usually end up with this on your class: override def lowPriority: PartialFunction[Any,Unit] = { case MyCaseClass1(a) => do something here case MyCaseClass2(a) …
fmpwizard
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partialFunction in collectFirst

I have a sequence of some objects and I want to collect the first element for which another function returns Some() For now, my code works this way: mySeq.collectFirst{ case elem if doSmth(elem).nonEmpty => (doSmth(elem).get, elem) } Is…
D Artem
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Partial function in scala

I see the following code in several places depicting the use of partial functions in Scala. val divide: PartialFunction[Int, Int] = { case d: Int if d != 0 => 42 / d } Here, divide is a variable whose type of is PartialFunction[Int,Int] which…
user3103957
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How to check if function is partial in Scala?

I have a method that receives a function, but that function may be partial, in such case I don't want it to fail with MatchError. def doSomething[X,Y](opt:Option[X])(f:X=>Y)={ f match { case p:PartialFunction[X,Y]=> opt.flatMap(p.lift) //This…
caeus
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In a pattern matching partial function, how to make isDefined return false for invalid inputs that can't be included in the case pattern?

In a partial function implemented with pattern matching, how to make isDefined return false for invalid inputs that can't be included in the case pattern? For example, I have the following decodeList partial function: case class Arr(items:…
Shreck Ye
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Why Scala PartialFunction works without defining isDefinedAt?

It looks First and Second are the same, but why? First val iter = List(1, 2, 3, 4, 5).iterator val first = iter.collect(new PartialFunction[Int, Int]{ def apply(i: Int) = i def isDefinedAt(i: Int) = i > 0 && i <…
mon
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In Scala, Is it possible to have a "partially lazy" calculaltion of a dynamically calculated partial function?

With assistance from @Luis Miguel Mejía Suárez, I have a dynamically calculated partial function for changing arabic numbers to roman numerals: import scala.collection.immutable.ListMap import scala.collection.mutable.StringBuilder object…
Brian Kessler
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Type-safe states with exhaustive pattern matching in Akka Typed

I started working with Akka Typed to get exhaustive pattern matching on my behaviors, which has been great for the external facing contract of each actor. However, if the actor is a state machine, chances are the different states have state specific…
Arne Claassen
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Scala function composition totalFn(partialFn(totalFn(x)))

I was trying to compose three functions with only the middle one being a PartialFunction. I would expect the resulting type to be PartialFunction as well. Example: val mod10: Int => Int = _ % 10 val inverse: PartialFunction[Int, Double] = { case n…
user2697852
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Scala missing parameter type for expanded function The argument types of an anonymous function must be fully known. (SLS 8.5)

I have the following snippet I need to complete for an assignment. To fulfill the asignment I have to correctly replace the comments /*fulfill ...*/. However I tried my best and I am still getting an missing parameter type for expanded function The…
HaaLeo
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Scala type inference failing to infer types of a generic function

I have the following code def sendMoney[T <: MoneyType](fn: T => Future[T], input: T): Unit which is called this way case x: Any => (sendMoney(_, _).tupled(x match { case c: HoldsMoney => (createHold(_: HoldsMoney), c: HoldsMoney) case r:…
ffff
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Scala, default code for PartialFunction?

I am using Akka and would like to run some code for all cases of a PartialFunction. For actor supervision, I have something like: val supervisorStrategy = OneForOneStrategy() { case npe: NullPointerException => Stop case re: RuntimeException =>…
ticofab
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