Questions tagged [scala]
Scala is a general-purpose programming language principally targeting the Java Virtual Machine. Designed to express common programming patterns in a concise, elegant, and type-safe way, it fuses both imperative and functional programming styles. Its key features are: an advanced static type system with type inference; function types; pattern-matching; implicit parameters and conversions; operator overloading; full interoperability with Java; concurrency
scala
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nested case class generic filter method
I have some nested case classes that may look like the following:
case class Lowest(intVal: Int, stringVal: String)
case class Mid (lowestSeq: Seq[Lowest])
case class High (midSeq: Seq[Mid])
So if ...
- 538
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19
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How to address the performance impact of executing multiple functions dynamically compiled with Scala 2's runtime reflection?
I have an entity that generates Scala functions compiled dynamically using Scala 2's runtime reflection. My case is slightly more convoluted, but the following showcases the issue:
import scala....
- 207
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Create Flow[ByteString, ByteString, NotUsed] by piping through InputStream
I need decompress data using compression not supported by akka, but supported by other library which provided InputStream interface.
To make it work with akka stream, I need to implement function:
def ...
- 23
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How to run MySQL scripts when I run docker compose? [duplicate]
I have a Scala backend and Javascript frontend applications and MySQL database. I want to create docker images for every one of them with one docker-compose.yml file and I want to run the scripts for ...
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0
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22
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Scala 3 reflection: collect all members that are singleton objects
I have a method in Scala 2 that uses reflection. It doesn't work in Scala 3, and I would like to reimplement it so it works for Scala 3. (I will no longer need it for Scala 2 anymore, so it need not ...
- 6,113
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27
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Chisel Template Not Functioning Windows 11 - Cannot run program "which": CreateProcess error=2, The system cannot find the file specified
After having cloned the template project for Chisel (https://github.com/chipsalliance/chisel-template) I tried running sbt test, and I got the following error in the file /src/test/scala/gcd/GCDSpec:
&...
- 35
1
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1
answer
47
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multiple pattern matching on iteration
val subjectpairs = IndexedSeq((8,0),(3,4),(0,9),(6,1))
val priors = subjectpairs.map { case( f,_) => f}.filter{ _ >0.0}
val posts = subjectpairs.map { case( _,l) => l}.filter{ _ >0.0}
...
- 9,645
1
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18
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Encrypt Spark Libsvm Dataframe
I have a libsvm file that I want to load into Spark and then encrypt it. I want to iterate over every element in the features to apply my encrypt function, but there doesn't seem to be any way to ...
- 41
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1
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17
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Adding new Rows to Spark Partition while using forEachPartition
I am trying to add a new Row to each Partition in my Spark Job. I am using the following code to achieve this:
StructType rowType = new StructType();
rowType.add(DataTypes.createStructField("...
- 1,081
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23
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IntelliJ Scala warning with parameterized type in compiled JAR
I have Scala code with parameterized types like this:
val foo: SomeParameterizedType[_ <: Product with Serializable] =
new SomeParameterizedType[Foo](arguments)
val bar: SomeParameterizedType[_ &...
- 18.5k
1
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28
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Unable to connect to MongoDB replicaset from scala mongodb driver
I am running mongodb replicaset in docker on localhost and I am able to connect to it from both command line and Mongodb Compass. When I try to connect from code I get Connection Refused. I am unable ...
- 5,036
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28
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Scala can't find imported file from same directory
I'm fairly new to scala, having troubles compiling my code. So I have a project structure like this
topdir/
com/
name/
final/
file1.scala
file2.scala
Both files are in the same package ...
- 103
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33
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IntelliJ Scala 2.13.0 no longer compiles - Error compiling the sbt component 'compiler-bridge-2.13.0-66.0'
I am working on a hobby project on my desktop using Scala 2.13.0 and JDK 22. The project compiles and runs perfectly fine there. This project is also on my personal GitHub. Because I went on holiday ...
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21
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Scala Spark Dataframe creation from Seq of tuples doesn't work in Scala 3, but does in Scala 2
When trying to test something locally with Scala Spark, I noticed the following problem and was wondering what causes it, and whether there exists a workaround.
Consider the following build ...
- 718
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39
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Using spark 3.4.1 lib in Java when extending StringRegexExpression to a java class
I am using spark 3.4.1 in maven project where I am configured scala (2.13.8) lang as well. I am trying to create a class Like.java in project by extending spark's StringRegexExpression
package com....
- 66
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38
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Scala project: sbt compile generates empty fs2-grpcs folder, missing proto-generated classes
I'm working on a Scala project that currently implements a simple REST API. I'm trying to add a new gRPC service to this project. However, I'm encountering an issue during compilation.
Issue:
When I ...
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1
answer
29
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How to resolve: java.lang.NoSuchMethodError: 'scala.collection.Seq org.apache.spark.sql.types.StructType.toAttributes()'
Running a simple ETL PySpark job on Dataproc 2.2 with job property spark.jars.packages set to io.delta:delta-core_2.12:2.4.0 . Other settings are set to default. I have the following config:
conf = (
...
- 21
1
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1
answer
53
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Scala Fs2: Aggregate computation on infinite streams
I cant seem to understand how to perform aggregate computations on infinite streams. Taking an infinite stream of elements and performing a computation on each one individually is easy, but collecting ...
- 11
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1
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64
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Azure Synapse Analytics - output not displayed
Following Scala code in Azure Synapse should print: Hello, World!. But instead, it prints: defined object Geeks.
Question: What could be the issue and how can we fix it?
object Geeks {
// Main ...
- 23.3k
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1
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Scala failed to install on Windows 10
I used this site to install Scala on latest version of Windows 10 Pro. The installer started and successfully completed the following steps (shown at the end below). At the end, command window asked: ...
- 23.3k
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1
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43
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Scala f interpolator formatting for Java LocalDate
I'd like to be able to format strings based on Java.LocalDate using the f interpolator, i.e. something like:
val = LocalDate.of(2024,7,28)
f"$dt:YYYY-MM-dd"
But this will give a compile ...
- 175
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0
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37
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Casting to a Member Type in Scala
I'm using the Apache POI library 5.2.3 in Scala to create a line chart in a PowerPoint presentation.
// createData returns XDDFChartData
var chartData = chart.createData(
ChartTypes.LINE,
...
- 31
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24
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Scalatest 3.0.8 PrivateMethodTester can't find private method named X
I have a base class that has a protected method called "validateOptPwd". This gets inherited in a test and then called via PrivateMethodTester.
val validateOptPwdMethod: PrivateMethod[Future[...
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1
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1
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36
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uPickle ReadWriter for joda DateTime fails
For a project, i need JSON representation for a org.joda.time.DateTime. For JSON, i use uPickle. As there is no implicit ReaderWriter[DateTime], i have to write it myself. After googleing around, i ...
-1
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0
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41
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How can I find if the current fiber is running in the primary or blocking thread pool [duplicate]
My app runs thousands of small tasks in parallel using foreachPar(){}.withParallelism(85). The app runs on a machine with 100 CPUs. Some tasks finish in a few milliseconds, while the others finish in ...
- 3,155