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
112,579
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Get compiler to notice exhaustive match on Vector
The following code defines an exhaustive match over a Vector, v.
def testExhaustiveness(v: Vector[Int]) = {
v match {
case Vector() => println("v is empty")
case ns :+ n => ...
- 949
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1
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11
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How to create data-frame on rocks db (SST files)
We hold our documents in rocks-db. We will be syncing these rocks-db sst files to S3. I would like to create a dataframe on the SST files and later run an sql. When googled, I was not able to find any ...
- 779
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How to force pull in fs2.Stream
I created an fs2.Stream with:
topic <- Stream.eval(fs2.concurrent.Topic[F, Either[Throwable, AmqpMessage[Array[Byte]]]])
messages <- Stream.resource(topic.subscribeAwait(innerQueueSize))
...
- 2,132
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Test/compile not finding lib/jar with Scala 3 (but 2.13 works)
I'm packaging jars from generated source code with an sbt-plugin and the jars are fine and on the classpath.
Now I have two identical minimal projects targeting Scala 2.13 and 3.3. With 2.13 I can run ...
- 5,817
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Scala 3 binary compatibility issue
As I am moving to help my organization adopt scala 3, i am trying to map out the potential chanllenge to look after.
Generally, i was readying about binary compatibility change with scala 3 and ...
- 9,684
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1
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38
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Scala Future strange behavior
What's wrong with this code? Why I can see only one output? What returns futureUserByName function? onComplete doesn't work for it as well. It must be just simple Future, but it doesn't work.
import ...
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Flattening nested json with back slash in apache spark scala Dataframe
{
"messageBody": "{\"task\":{\"taskId\":\"c6d9fb0e-42ba-4a3e-bd39-f2a32a6958c1\",\"serializedTaskData\":\"{\\\"clientId\\\":\\\&...
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Jetty 12 with Scala "Unable to locate class corresponding to inner class entry for Scope"
After upgrading jetty-server from 11 to 12, the compilation (using mill as the build tool) fails with:
Unable to locate class corresponding to inner class entry for Scope in owner org.eclipse.jetty....
- 341
1
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1
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54
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Scala 3 macros: "dynamically" instantiating singleton objects at compile-time
I'm trying to create a macro that makes use of some objects.
Suppose I have the following definitions:
trait Foo:
def doStuff(): Unit
// in other files
object Bar extends Foo:
def doStuff() = ......
- 485
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72
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Importing libraries with same names
I have two libraries that both follow the same names for importing, but one has more functionality than the other. How do I make scala choose the right library to use when importing? Currently, it’s ...
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Comparing impact of Scala PlayFramework's db.withConnection and db.withTransaction methods on the underlying postgres database
Given that there is just one simple SQL statement (example: select id from foo) that I need to execute on my Postgres 15 database, I am curious to know the performance impact of executing it using ...
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23
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Spark : Read special characters from the content of dat file without corrupting it in scala
I have to read all the special characters in some dat file (e.g.- testdata.dat) without being corrupted and initialise it into a dataframe in scala using spark.
I have one dat file (eg - testdata.dat),...
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1
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29
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Use Jedis `echo` in pipeline
The examples use Scala code, but the issue would be the same with Java.
Way back in version 2 of Jedis, you could use echo in a pipeline:
import redis.clients.jedis._
object Main {
def main(args: ...
- 341
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1
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38
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Scala 2 to Scala 3: Instantiating a trait no longer recognises new methods
The following code compiles and runs in Scala 2:
trait SomeTrait {
val myName: String
}
class SomeClass() extends SomeTrait {
override val myName: String = "Billy Banana"
}
val ...
- 83
1
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24
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Creating a custom aggregator in spark with window rowsBetween?
What I'm trying to do is use a window function to get the last and current row and do some computation on a couple of the columns with a custom aggregator. I have time series data with points that are ...
- 91