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: ... .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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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 ... 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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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 ... 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 ... 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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scala reflection

I want to create a hashmap to store parameters names and their values. The parameters however are with different ... 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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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. ... 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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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 ... 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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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 #:: ... 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 ... 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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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 ... => 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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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 ... 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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876 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, ... 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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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. ... 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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775 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 ... 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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745 views

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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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620 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. ... ? 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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584 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 ... 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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611 views

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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 ... 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

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scala - Predict Class Probabilities in Spark RandomForestClassifier

I built random forest models using ml.classification.RandomForestClassifier. I am trying to extract the predict ... 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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697 views

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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 ... .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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595 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 ... 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( ... 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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858 views

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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 ... 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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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 ... 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 ... 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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748 views

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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 ... 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

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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 ... 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 ... 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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