Recent questions tagged scala

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scala - flatMap with Shapeless yield FlatMapper not found

I'm trying to define some structure like this case class Transformer[From, To]( name: String, get: PaymentEvent => From, to: From => To I want ... ],shapeless.HNil]]] fields.flatMap(new filterName(names)) See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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623 views

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scala - Parametric type + function requires a string as second parameter?

class TestClass[T](val x: T) { def +(other: TestClass[T]) = x + other.x } this definition gives me the following compile error: error: type ... Double as a type parameter and use addition in Scala?? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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855 views

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scala - How to hide scrollbars in the JavaFX WebView

I'm trying to remove the scrollbars in a javafx webview. Search on forums, the suggestion is to make them invisible as follows: browser.getChildrenUnmodifiable( ... is surrounded in Scala code. Thanks! S See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Spark join produces wrong results

Presenting here before possibly filing a bug. I'm using Spark 1.6.0. This is a simplified version of the problem I'm dealing with. I've filtered a ... bug, or is this expected behaviour? If expected, why? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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634 views

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scala reflection

I want to create a hashmap to store parameters names and their values. The parameters however are with different types. I could use HashMap[String, Any], but ... Or is there any better way to store pair? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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641 views

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scala - Error when trying to write to hdfs: Server IPC version 9 cannot communicate with client version 4

I am trying a write a file to hdfs using scala and I keep getting the following error Caused by: org.apache.hadoop.ipc.RemoteException: Server IPC version 9 ... What change should I do to make this work? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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849 views

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scala - Add additional directory to clean task in SBT build

I have a SBT build where the tests create temporary files into a directory called temp. How can I tell SBT to delete this folder when I call the clean task? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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691 views

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scala - Why can't i define a variable recursively in a code block?

Why can't i define a variable recursively in a code block? scala> { | val test: Stream[Int] = 1 #:: test | } <console>:9: error: forward ... a code block but throws a compilation error in a code block. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Spark DataFrame equivalent to Pandas Dataframe `.iloc()` method?

Is there a way to reference Spark DataFrame columns by position using an integer? Analogous Pandas DataFrame operation: df.iloc[:0] # Give me all the rows at column position 0 See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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569 views

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scala - Difference in flattening an Option[List[Int]] in 2.9.1 and 2.10 nightly

I get different behaviour in 2.9.1 and 2.10 nightly -- what changed? Welcome to Scala version 2.9.1.final (OpenJDK Client VM, Java 1.6.0_22). Type in ... Some(3) map (x => List(x, -x)) flatten See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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1.1k views

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scala - sbt-assembly : including test classes

As part of sbt-assembly I want to include both src and test class files in jar. Sbt-assembly includes only src files with dependencies. Is there any way ... I can include test classes also in same jar? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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870 views

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scala - How to concatenate two streams in Apache Flink

E.g. i want to compose stream of 1, 2, 3 and 4, 5 in single one, so result should be: 1, 2, 3, 4, 5. In other words: if ... that Also did similar attempt with datetime included, but with same result. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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758 views

1 answer

scala - Non-integer ids in Spark MLlib ALS

I'd like to use val ratings = data.map(_.split(',') match { case Array(user,item,rate) => Rating(user.toInt,item.toInt,rate.toFloat) }) val model ... may produce error. How can i do to solve the problem? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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771 views

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scala - How to create encoder for Option type constructor, e.g. Option[Int]?

Is it possible to use Option[_] member in a case class used with Dataset API? eg. Option[Int] I tried to find an example but could not find any ... I moved the case class outside of the Main function. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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743 views

1 answer

scala - Why can I not flatMap a List[Option] using underscore?

Why can I write val flat: List[Int] = List(Some(1), Some(2)).flatMap(i => i) But not val flat: List[Int] = List(Some(1), Some(2)).flatMap(_) See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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619 views

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scala - Spark Dataset aggregation similar to RDD aggregate(zero)(accum, combiner)

RDD has a very useful method aggregate that allows to accumulate with some zero value and combine that across partitions. Is there any way to do that with ... capable of doing the same? Thanks a lot! VK See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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580 views

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scala - Cross-compiling aggregate projects with different crossScalaVersions for subprojects

We have a project with several subprojects which can compile under both Scala 2.10 and 2.11, one subproject which only compiles under 2.10 ( ... the aggregate project and still avoid this problem? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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608 views

1 answer

scala - NullPointerException in Spark RDD map when submitted as a spark job

We're trying to submit a spark job (spark 2.0, hadoop 2.7.2) but for some reason we're receiving a rather cryptic NPE in EMR. Everything runs just ... Also, how can we resolve it? We're pretty stumped. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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637 views

1 answer

scala - Predict Class Probabilities in Spark RandomForestClassifier

I built random forest models using ml.classification.RandomForestClassifier. I am trying to extract the predict probabilities from the models but I only saw ... share your thought or solutions. Thanks! See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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695 views

1 answer

scala - How to convert List[Double] to Columns?

I have List[Double], how to convert it to org.apache.spark.sql.Column. I am trying to insert it as a column using .withColumn() to existing DataFrame. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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593 views

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scala - Load Spark data locally Incomplete HDFS URI

I have experienced a problem with SBT loading in a local CSV file. Basically, I've written a Spark program in Scala Eclipse which reads the ... not (despite working under home/projects directory). See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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796 views

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scala - Gatling - execute scenarios sequentialy

When I run code like: setUp( scenario1.inject(constantUsersPerSec(1) during (1 second)), scenario2.inject(constantUsersPerSec(1) during (1 second)) ).protocol() ... to be changed to run it one by one? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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854 views

1 answer

scala - Play tests with database: "Too many connections"

To have a database available in scalatest with evolutions I use this extension of the default PlaySpec inspired by this SO question: trait ResetDbSpec extends PlaySpec with ... Play 2.5.10 and Slick 3.1. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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711 views

1 answer

scala - Can I overload curried methods?

Is there a way to overload methods in Scala that take multiple parameter lists? E.g. I'd like to do this: def foo(a: Int)(b: Int)(c: ... parameter might be considered optional in some cases, for example. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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1.0k views

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scala - Read specific column from Parquet without using Spark

I am trying to read Parquet files without using Apache Spark and I am able to do it but I am finding it hard to read specific columns. I am not ... columns from the file. I want to read specific columns. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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744 views

1 answer

scala - Using dynamic Datasource with Tomcat

I'm creating a series of webservices for my application and i have the need to access a different database based on the serviceCode that is passed as a ... or am i forced to add a resource everytime? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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560 views

1 answer

scala - What does Dotty offer to replace type projections?

I have been reading about Dotty, since it looks like it is about to become scala 3, and noticed that type projections are deemed "unsound" and removed ... so that we can cache the result in container } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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731 views

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scala - Unresolved Dependencies when building play 2.0 project

Downloaded play-2.0 from type safe yesterday, following instructions as far as I can, but when I come to build with sbt I get unresolved dependency ... appreciate any guidance on where to look... Thanks See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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