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].
Questions tagged [partialfunction]
120 questions
0
votes
1 answer
Type mismatch in Play controller action when recovering a future
I'm having a problem to return the correct type in a scala play controller method can someone give me a hint here? I'm using for comprehantion to deal with two service methods that returns a Future, and I would like to handle elegantly the result…
simonC
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0
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1 answer
How are we creating an object for a trait?
If PartialFunction is a trait, then how does this code work? Are we creating an object of the trait?
def x=new PartialFunction[Any, Unit] {
def isDefinedAt(x: Any) = x match {
case "hello" => true
case "world" => true
case…
codingsplash
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0
votes
1 answer
What does @ mean in Scala?
When studying sources of akka I found the following in the akka.event.slf4j.SLF4JLogger actor:
def receive = {
//...
case event @ Warning(logSource, logClass, message) ⇒
withMdc(logSource, event) { Logger(logClass,…
user2953119
0
votes
1 answer
Scala Partial Function Application Semantics + locking with synchronized
Based on my previous question on locks based on value-equality rather than lock-equality, I came up with the following implementation:
/**
* An util that provides synchronization using value equality rather than referential equality
* It is…
pathikrit
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1 answer
How to combine PartialFunction with another function and return PartialFunction?
I have the following class:
class MessageProcessorActor(private val destination : ActorRef) extends Actor{
override def receive: Receive = {
case _ =>
destination ! {
case MyActor.TracableMessage(msg) =>…
user3663882
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0
votes
1 answer
Is there something like Map.keySet for a partial function in scala?
More specifically, I have:
case class Key (key: String)
abstract class abstr {
type MethodMap = PartialFunction[Key, String => Unit]
def myMap: MethodMap // abstract
def useIt (key: Key, value: String) = {
val meth = myMap(key)
…
Mahdi
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0
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1 answer
How to implement a partial function in a subclass
I'm trying to design a couple of classes that inherit a partial function, but I don't seem to be able to get the syntax quite right. My superclass looks like this:
abstract class Controller {
val react:PartialFunction[Event,Unit]
}
And the…
Ceilingfish
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0
votes
1 answer
implicit from context bound on collection type parameter
I have some code that streams a response by converting a Stream of case classes to json representations using spray.json. This works fine for a single case class, but I want to genericize it.
So I'm starting with case classes like this:
import…
ryryguy
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0
votes
1 answer
Partial Functions and Execute-Once behaviour in Scala
EDIT: I agree with the sentiment of the down vote, but disagreed with the solution. So I've corrected/broken the code in the question so it has the problem as explained. I've left the answer and my original comment to it. In my opinion, the "def…
Tom
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votes
2 answers
Scala regex and partial functions
I want to use Scala's collect function with a regular expression. Ideally I'd like to collect only those terms that match the regular expression. I've so far implemented the following which works fine
val regex =…
Jon
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0
votes
1 answer
Scala: Function definition of PartialFunction is ambiguous
Function definition of the PartialFunction is following:
trait PartialFunction[-A, +B] extends (A) ⇒ B
PartialFunction would allow us to filter by using case with collect on collection.
For example when you have list of integers and…
user_1357
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0
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1 answer
How does the case by type work in scala?
I know about case classes, pattern matching, unapply and PartialFunction, but I'm confused about bellow macros snippet.
val declarations = weakTypeOf[T].declarations
val methods = declarations.collect { case m: MethodSymbol => m }
Scaladoc of…
sh1ng
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0
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1 answer
Scala Currying: Overriding function with an empty argument by a partial function
I'm trying to implement/override a function with an empty input argument by using partial function. It is best explained by this non-working minimal example:
trait T
trait TFactory {
def build(): T
}
class A(someParameter: Int) extends T
object…
bluenote10
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3 answers
Scala PartialFunction construction with different results
I was trying to debug why some partial function composition were not working when I noticed that depending on how you instantiate the partial function you get different results.
When you're using the syntactic sugar method it all works as…
Cristian Vrabie
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-1
votes
1 answer
Scala: Partial function error: use _ if you want to treat it as a PartialFunction
The following piece of code does not work:
FileSystems.getDefault.getPath is from the java.nio package
Update:
Method createCalculation is:
Note: MyLocation is a case class that extends MyMessage
def creatCalculation(myPlace: MyLocation): MyMessage…
user3825558
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