Operator priority for sum and division on the list in Scala

My example uses sum function but this is not the only higher order function I've been having problems with. To the point It's been a while but I keep catching myself on writing code like: scala> List(2, 5, 7, 11) sum / 3 which gives me: <console>

Why does not my card () work?

I have a Akka HTTP service which returns a string, as shown below: val route1: Route = { path("hello") { get{ complete{ println("Inside r1") "You just accessed hello" } } } } I am trying to understand the difference between m

How to access nested fields in the .proto, ScalaPB database

The following my dataframe schema root |-- name: string (nullable = true) |-- addresses: array (nullable = true) | |-- element: struct (containsNull = true) | | |-- street: string (nullable = true) | | |-- city: string (nullable = true) I want to out

logical and if inside scala match cases

I need to use bunch of match case in scala, how do I use for or if inside the match case, so for example: import scala.util.Random val x = Random.nextInt(30) val result = match x { case 0 to 10 => bad case 11 to 20 => average case 20 to 30 => coo

Benefits of creating a type alias versus using a string

I can see a few benefits of creating a custom type over using a string for things like: type UserId = String def getUser(userId: UserId)... versus: def getUser(userId: String)... It makes your code more readable, and I imagine if you ever need to cha

Is there a beach data structure in Scala?

I'm looking for a way to handle ranges in Scala. What I need to do is: given a set of ranges and a range(A) return the range(B) where range(A) intersect range (B) is not empty given a set of ranges and a range(A) remove/add range(A) from/to the set o

Apache Spark RDD [Vector] Immunity Problem

I know the RDDs are immutable and therefore their value cannot be changed but I see the following behaviour: I wrote an implementation for FuzzyCMeans (https://github.com/salexln/FinalProject_FCM) algorithm and now I'm testing it, so I run the follow

Returns the elements of the array, except to repeat

Write a method that returns the values of all elements in the array, except for repeating. Do not use for. - this is task from Scala book. I tried myArray.mkString(", ") but it has duplicates. Searched into Scaladoc but it doesn't help. Maybe tr

Add only unique items to a list from another list

I am creating a service that returns lists of articles from an XML feed. I am trying to find a better way to update the list of articles currently stored in my program whenever the client code calls for an update. I have a variable named articleHisto

How to specify the parameter of the function with implicit?

I would like to pass a function with signature def insert(o: Role)(implicit s: Session): UUID into a function (as inserter) with signature def insertRows[T](instanceList: List[T], inserter: T => UUID): Unit How do I specify that inserter has an impli

Scala: best nested multiple-condition test

Lately, I frequently end up writing code like that: def doSomethingWithLotsOfConditions(arg1, arg2, arg3...) { arg1.get(arg2) match { case Some(value1) => arg3.get(value1) match { case Some(value2) => arg4.get(arg5, value2) match { case Some(value3)

Are parcelables from Android supported by Scala?

I've read that due to Scala compiler magic it is possible to implement the Android Parcelable pattern in Scala (that requires a static class member). However there is very little information about that and I'm not sure ... ... if this is even true ..

Extraction of entities and nested values ​​from JSON

I am trying to extract Issues from Jira and put them into List[Issue]. I figured out how to download and parse JSON: val json = JsonParser.parse(content) I can also extract some numbers in the root of JSON: val total = (json \ "total").extract[I

Play scala json frame validation exception

I'm trying to check JsValue object in my Actor using play framework 2.2.2. When I try to use validate method, I receive exception not a result object: try { val result = data.validate[EventConfig] Logger.debug("Result: "+result") } catch {

Scala overloaded higher order functions cause a type error

I have a overloaded method defined as follows: def g(f: () ⇒ Double): Object = null def g(f: Double ⇒ Double): Object = null def g(f: (Double, Double) ⇒ Double): Object = null def h(f: (Double, Double) ⇒ Double): Object = null While h(math.max _) wor

Scala - select items from the ordered list

I am looking for a nice way to remove first N elements which are equal from the ordered list, e.g. List(1,1,1,2,3,3) should return removeSame(list) -> (1,1,1) Is there a nice way to do it, rather than remove the head of the list and then use takeWhil

Scala Lift - Run PHP file since scala run

I'm not entirely sure the wording for the title is correct, but what I'm attempting to do is run and execute PHP files from within the Lift framework. I'm not after any url queries to a PHP file residing on a server, more interested in somehow gettin

How to implement instance sharing for case classes

Assuming defintion: case class IntegerWrapper(i : Int) and being in a situation that potentially large amounts of IntegerWrapper instances with i=[0..N> may be created what does one have to do to: Map this range to a fixed set of singletons [IntegerW

Features vs. Scala packages

After watching Martin's keynote on Reflection and Compilers I can't seem to get this crazy question out of my head. Martin talks among other things about the "(Wedding) Cake Pattern", where traits play the central part. I'm wondering, why in the

Step by step guide for Scala to work on .net?

I have never used .Net framework and need to demonstrate to someone that Scala indeed works on .Net. I need to get a "quick and dirty" .Net setup with Scala working on some existing JVM Scala code. I could not find a step-by-step guide for this.

using a partial function to block the block with scala

I have a catch block that I end up repeating quite a bit, and found this SO question that confirmed that I can use a partial function as a catch block (What are the use cases for Scala 2.9's try-catch generalization? 1). Currently, my code looks like

Do the constructor arguments get GC'ed?

I am using a system which needs to initialize many objects using transactions, and for reasons beyond the scope of this question these transactions must be passed into the constructors. Like this: trait Mutable class Txn(i: Int) { def newID(implicit

Why is there no string interpolation in Scala?

This is not just an idle quip... I wonder if anybody knows if there's an actual design reason why Scala does not support interpolation similar to Groovy and other "syntactically better Javas"? e.g. var str1 = "World"; var str2 = "