Recent questions tagged Scala

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scala - Liftweb: create a form that can be submitted both traditionally and with AJAX

Is it possible in Lift web framework to create forms (and links) that react via AJAX, but also work without ... code, that would be best. 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 SQL filter multiple fields

What is the corrent syntax for filtering on multiple columns in the Scala API? If I want to do something like this: ... "group" !== "-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 - If case class inheritance is prohibited, how to represent this?

I am trying to create the case classes as explained in this article sealed abstract case class Exp() case class ... (x:Int) extends Exp ^ 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 - Turn Slick logging off

Slick fills up the console with a massive amount of log messages. I wanted, like the documentation suggested, ... - After phase insertCompiler: 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 compile single file in sbt

I'm doing some refactoring that made compiler temporally give errors in several files. I'd like to work ... that sbt functionality disclosure. See Question&Answers more detail:os...

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

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800 views

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scala - How does curly braces following trait instantiation work?

I find some confusing use of trait in some unittesting code, such as: trait MyTrait { val t1 = ... // ... other cases might also be helpful? 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 find max in a list of tuples?

I have the following list of tuples: val arr = List(('a',10),('b',2),('c',3)) How to find the tuple ... or ('a', 10) for max value. 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 - Inheriting a trait twice

This doesn't work: trait Trait class Class extends Trait with Trait Compiler complains: <console>:8: error: ... or pattern somehow useful? 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 convert X => Option[R] to PartialFunction[X,R]

As long as we have a PartialFunction[X,R] it's very easy to convert it to a function returning Option[R], ... there some better way I missed? See Question&Answers more detail:os...

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

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938 views

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scala - Match "fallthrough": executing same piece of code for more than one case?

What is the Scala's way to write the following code: int i; switch(i) { case 1: a(); break; case ... code will return nothing. Thanks for help! See Question&Answers more detail:os...

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

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810 views

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scala - Play2 Framework proxy streaming content to client keeps connection open after streaming is done

The below code does streaming back to client, in, what I gather is a more idiomatic way than using Java's ... when passed through this proxy. See Question&Answers more detail:os...

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

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894 views

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scala - Spark: sc.WholeTextFiles takes a long time to execute

I have a cluster and I execute wholeTextFiles which should pull about a million text files who sum up to ... to observe the limit... See Question&Answers more detail:os...

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

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699 views

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scala - Testing a Play2 application with SecureSocial using dependency injection

Thanks a lot for any guidance! The SecureSocial plugin works fine when I run it from the browser, but I would ... apply(Action.scala:215) [info] See Question&Answers more detail:os...

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

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707 views

1 answer

scala - Why makes calling error or done in a BodyParser's Iteratee the request hang in Play Framework 2.0?

I am trying to understand the reactive I/O concepts of Play 2.0 framework. In order to get a better ... this I would greatly appreciate it! See Question&Answers more detail:os...

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

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754 views

1 answer

scala - Why method defined like "cons[B >: A](v: B)" accepts argument of type which is not supertype of A?

I am studying variance in scala right now, and I think I have a good understanding of contravariance. For example given ... >: A is not true. See Question&Answers more detail:os...

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

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790 views

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scala - How to do custom operations on GroupedData in Spark?

I want to rewrite some of my code written with RDDs to use DataFrames. It was working quite smoothly until ... possible? Thanks in advance. See Question&Answers more detail:os...

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

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1.5k views

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scala - Spark dataframe checkpoint cleanup

I have a dataframe in spark where an entire partition from Hive has been loaded and i need to break the lineage ... has been in the dataframes. 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 - How to read and write multiple tables in parallel in Spark?

In my Spark application, I am trying to read multiple tables from RDBMS, doing some data processing, then write ... (I think same logic)? See Question&Answers more detail:os...

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

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902 views

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scala - Iterate Over a tuple

I need to implement a generic method that takes a tuple and returns a Map Example : val tuple=((1,2),( ... this kind of iteration over the tuple 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 - merge multiple small files in to few larger files in Spark

I using hive through Spark. I have a Insert into partitioned table query in my spark code. The input data is in ... to do this Spark or 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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924 views

1 answer

scala - Macro to access source code text at runtime

Is there already or is it possible to have a Scala macro that gives me access to the text of the source? For ... "} // prints list.sum: 6 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 - Is there any difference between flatten and flatMap(identity)?

scala> List(List(1), List(2), List(3), List(4)) res18: List[List[Int]] = List(List(1), List(2), ... one over the other? Are there any tradeoffs? See Question&Answers more detail:os...

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

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1.2k views

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scala - Dropping empty DataFrame partitions in Apache Spark

I try to repartition a DataFrame according to a column the the DataFrame has N (let say N=3) different values ... creates 200 partitions) ...) See Question&Answers more detail:os...

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

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719 views

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scala - Continuations and for comprehensions -- what's the incompatibility?

I am new to Scala and trying to wrap my head around continuations I'm trying to reproduce the yield return C# ... than a while loop? Thank you 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

1 answer

scala - Shapeless: generic lens parameterized by case class or field

Based on: import shapeless._ case class Content(field: Int) lens[Content] >> 'field I am trying to ... boilerplate-free 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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817 views

1 answer

scala - Is there an Iteratee-like concept which pulls data from multiple sources?

It is possible to pull on demand from a number (say two for simplicity) of sources using streams (lazy lists). ... source does it want to pull. See Question&Answers more detail:os...

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

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955 views

1 answer

scala - How to generate type hierarchy diagrams with Scaladoc?

I want that Scaladoc generates a type hierarchy diagram for the following code snippet: trait A trait B extends ... I generate such diagrams? 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

1 answer

scala - How to set heap size in play/activator?

I get a "java.lang.OutOfMemoryError: Java heap space" when running activator. I would like to set the ... any documentation on this anywhere. See Question&Answers more detail:os...

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

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