implicit

Apparently unapply/unapplySeq in extractor objects do not support implicit parameters. Assuming here an interesting parameter a, and a disturbingly ubiquitous parameter b that would be nice to hide away, when extracting c. [ EDIT ]: It appears something was broken in my intellij/scala-plugin installation that caused this. I cannot explain. I was having numerous strange problems with my intellij lately. After reinstalling, I can no longer reprodce my problem. Confirmed that unapply/unapplySeq do allow for implicit parameters! Thanks for your help. This does not work (**EDIT :yes, it does):**

The following example from A Tour of Scala shows how implicit can be used to provide the appropriate missing members (add and unit) based on the type. The compiler will pick the right implicit object in scope. The library also uses that with List.sortBy and Ordering or List.sum and Numeric for instance. However is the following usage in class B a valid/recommended usage of implicit parameters (as opposed to not using implicit in class A): class I class A { def foo(i:I) { bar(i) } def bar(i:I) { baz(i) } def baz(i:I) { println("A baz " + i) } } (new A).foo(new I) class B { def foo(implicit i:I)

There are, at least, two techniques in Scala to pass default value to a method 1) default parameter value scala> def f(i: Int = 0) = i f: (i: Int)Int scala> f() res0: Int = 0 scala> f(1) res1: Int = 1 2) implicit parameter scala> def g(implicit i: Int) = i g: (implicit i: Int)Int scala> implicit val default = 0 default: Int = 0 scala> g(1) res5: Int = 1 scala> g res7: Int = 0 In which case do you choose one or another ? With the power of implicit, default values are they a usefull feature ? You should definitely prefer default parameter value. You should never create or use implicit parameters

Consider the following code: class A { def print = println("A") } class B extends A { override def print = println("B") } def foo(implicit a: A) = a.print def bar(implicit a: A) = { implicit val b = new B foo } bar(new A) // B I am wondering why calling foo in bar isn't raising an ambiguous implicit values error. Of course implicit val b: A = new B will raise that error. Why does foo pick the implicit b and not the implicit a ? Or even more general: What are the rules what will be picked? EDIT: Due to my comment-conversation with Ivan I want to clarify: I would know the answer to my question

I have a record type with methods, representing an specific hardware measurement type, read from the instrument as a string. The record contains implicit coversion to (and from) a string. If I cast a string as a record type, it seems to work, but is this safe? That is, does casting a string to a record with implicit string conversion call the implicit conversion as per assigning a temporary value? var a: MeasurementRecord; // record type with implicit string conversion & decode methods b: string; c:double; begin b := Edit1.Text; // Or any other string source a:=b; //Ok a:= edit1.text; //Ok c:=

I have a method that takes type parameters with an implicit view bounds on them. Can I use the @implicitNotFound annotation to give nicer compiler errors when the method is called with invalid data types? The documentation for the method is useless and even the source code doesn't help, and all the examples of use online are at the trait or class level. No, you cannot directly do that. As you’ve noticed, @implicitNotFound annotates traits or classes. You could, however, make a special implicit type just for that method and annotate it if you really wanted to have a custom message. 来源： https:/

I thought Implicit linking loads a DLL as soon as the application starts because it is also called "load-time dynamic linking". But I found some strange explanations below from the link here( https://msdn.microsoft.com/en-us/library/253b8k2c(VS.80).aspx ). Implicit Linking Like the rest of a program's code, DLL code is mapped into the address space of the process when the process starts up and it is loaded into memory only when needed. As a result, the PRELOAD and LOADONCALL code attributes used by .def files to control loading in previous versions of Windows no longer have meaning. Explicit

I am facing a strange issue with Scala/Spark (1.5) and Zeppelin: If I run the following Scala/Spark code, it will run properly: // TEST NO PROBLEM SERIALIZATION val rdd = sc.parallelize(Seq(1, 2, 3)) val testList = List[String]("a", "b") rdd.map{a => val aa = testList(0) None} However after declaring a custom dataframe type as proposed here //DATAFRAME EXTENSION import org.apache.spark.sql.DataFrame object ExtraDataFrameOperations { implicit class DFWithExtraOperations(df : DataFrame) { //drop several columns def drop(colToDrop:Seq[String]):DataFrame = { var df_temp = df colToDrop.foreach{

lazy val productService = BeanLookup[ProductDataService] object BeanLookup { def apply[T](implicit manifest: Manifest[T], context: ActorContext) = { val beanLookup = context.actorFor("/user/spring/beanLookup") Await.result( (beanLookup.ask(LookupBean(manifest.erasure))(timeout)).mapTo[T](manifest), timeout.duration) } def apply[T](implicit manifest: Manifest[T], system: ActorSystem) = { val beanLookup = system.actorFor("/user/spring/beanLookup") Await.result( (beanLookup.ask(LookupBean(manifest.erasure))(timeout)).mapTo[T](manifest), timeout.duration) } } scalac complains : scala: ambiguous

I've not been able to come up with how to encode Obj in Scala: {-# LANGUAGE ExistentialQuantification #-} data Obj = forall a. (Show a) => Obj a instance Show Obj where show (Obj a) = "Obj " ++ show a main = print $ show [Obj "hello", Obj 3, Obj True] when run, the above produces the following output: [Obj "hello",Obj 3,Obj True] In Scala, however, this does not seem to compile: forSome { type T; implicit val ev: Show[T] } and neither does this: forSome { type T : Show[T] } Is this even possible at the type system level, or do I need to "capture" the type class instance using something like