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
2
votes
0 answers
A toArray function that breaks on primitive type, but works fine when written as a PartialFunction?
Playing around with a reflection-base code I've come a cross a situation where I want to convert a sequence into array. The catch is that the only type information available is in the form of a runtime.universe.Type, and the sequence itself is of…
Worakarn Isaratham
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2
votes
3 answers
How to convert one partial function to another?
Suppose I've got partial function parf
val parf: PartialFunction[Int, String] = { case 0 => "!!!" }
Now I've got also case class A(x: Int) and I need a function to transform PartialFunction[Int, String] to PartialFunction[A, String]:
def foo(pf:…
Michael
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2
votes
2 answers
How to return early in a pattern match of akka actor receive
Tried googling variations on this trivial question but didn't get an answer...
Basically I have a pattern match in my receive method.
In some cases I want to break early from the receive handling
override def receive = {
case blah => {
…
Avba
- 14,822
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2
votes
2 answers
What is the reference of the object that a partial function matches on?
Looking at this function as an example:
def receive = {
case "test" => log.info("received test")
case _ => log.info("received unknown message")
}
What object is being matched on? On the right hand side of the arrows, how can I refer to the…
Nelson
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2
votes
1 answer
What is correct way to use operator orElse in Scala?
I want to write two services, and then use orElse to make the two services combine together, which means service_one or service_two. They are all
PartialFunctions.
The service one is:
val usersService = HttpService {
case request @ GET -> Root /…
user504909
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2
votes
3 answers
Variable arguments with partial applied functions
I have a compilation problem on the following code.
object Main {
def main(args:Array[String]) = {
def collectBigger(median:Int)(values:Int*) = values.filter { _ > median }
val passedRanks = collectBigger(5)_
//this compiles
…
raisercostin
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2
votes
1 answer
Scala PartialFunction Stackoverflow
I'm developing a Scala / Python library called PySpark Cassandra. In it I have to deal with objects serialized Python objects in the pickle format when e.g. saving data.
I have a job which fails with a stackoverlfow:
org.apache.spark.SparkException:…
Frens Jan
- 319
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2
votes
2 answers
Scala : Overloaded function with PartialFunction in argument
I've just come across a strange problem while trying to overload a function using a partial function :
class Foo {
def bar(pf: PartialFunction[String, Int]): Foo = ???
def bar(zd: Int): Foo = ???
def zed(pf: PartialFunction[String, Int]): Foo…
Francis Toth
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2
votes
2 answers
inexplicable for-comprehension result in Scala
I understand for-expression is translated into map and flatMap. But I found something that I can not explain and need your helps. Here are two toy examples:
for {
None <- List(Option(1),None)
} yield 0
//res0: List[Int] = List(0, 0)
Q1: Why…
WeiChing 林煒清
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2
votes
1 answer
Scala regex + partial function unapply performance
Assume that I have a code like:
val pf: PartialFunction[String, Unit] =
"string" match { case regex(g1, g2, _*) =>
function(g1, g2)
}
pf has methods isDefinedAt and apply. Will the regex search be evaluated once, in isDefinedAt point, or…
dveim
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2
votes
1 answer
Scala function partial application
I'm trying to understand how function partial application works in Scala.
To do that, I've built this simple code:
object Test extends App {
myCustomConcat("General", "Public", "License") foreach print
…
nolanofra
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2
votes
2 answers
Collect results of multiple partial functions at single value?
Suppose I have some partial functions that may have overlapping domains:
val funcs: Seq[PartialFunction[Any, Int]] = Vector(
{ case i: Int if i % 2 == 0 => i*2 }
,
{ case i: Int if i % 2 == 1 => i*3 }
,
{ case i: Int if i % 6 == 0 => i*5 }
)
I want…
Arkadiy Kukarkin
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2
votes
1 answer
How to use PartialFunction.applyOrElse
I have a PartialFuncton[Throwable,Future[Result]] called errorMap to transform an throwable to a result or failed future. I can do it via lift and getOrElse like this:
val x: Future[Result] = errorMap.lift(e).getOrElse(Future.failed(e))
I figure…
Arne Claassen
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2
votes
1 answer
How to mix PartialFunction input parameter with output
What is the best way to mix a function input parameter with the output.
Here is my current code :
def zip[A,B](f: A => B) : A => (A, B) = (a: A) => (a, f(a))
def zip[A,B](pf: PartialFunction[A,B]) : PartialFunction[A, (A, B)] = {
case a if…
Yann Moisan
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2
votes
1 answer
Scala: 'missing parameter type' when calling scala macro with a PartialFunction reify
The compiler is throwing me a 'Missing parameter type'. After cornering the problem I've realized that when chaining Partial Functions you need to be explicit about the types or the compiler will throw the mentioned error. Now, do you guys know if…
ernestRC
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