Recent questions tagged scala

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scala - Why is List a Semigroup but Seq is not?

I'm fairly new to scalaz and I am trying to figure out why the following code works: import scalaz._ import Scalaz ... isn't there one for Seq? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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658 views

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scala - Turning A => M[B] into M[A => B]

For a monad M, Is it possible to turn A => M[B] into M[A => B]? I've tried following the types to no ... , so I'm not holding out much luck. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Spark job with Async HTTP call

I build a RDD from a list of urls, and then try to fetch datas with some async http call. I need all the ... t find any answer yet. Best regards See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Changing Ivy Cache Location for sbt projects in IntelliJ IDEA?

I have sbt 0.13.2 with a Scala project in IntelliJ 13.0.2. I just want to change my default ../. ... update SBT_HOME What would be the solution? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Spark UDF for StructType / Row

I have a "StructType" column in spark Dataframe that has an array and a string as sub-fields. I'd like ... value register with alternatives: ... See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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658 views

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scala - Intermittent Timeout Exception using Spark

I've a Spark cluster with 10 nodes, and I'm getting this exception after using the Spark Context for the first ... cluster know how to solve it? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - case class copy 'method' with superclass

I want to do something like this: sealed abstract class Base(val myparam:String) case class Foo(override val ... of Edmondo1984's response. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Is there any way to extend an object?

In scala, we cannot extend object: object X object Y extends X gives an error error: not found: type X In ... easiest way to extend this object? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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535 views

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scala - How to check covariant and contravariant position of an element in the function?

This is a code snippet from one of the articles that I read regarding contravariance and covariance in scala. ... be highly helpful. Thanks See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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676 views

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scala - Calculate the standard deviation of grouped data in a Spark DataFrame

I have user logs that I have taken from a csv and converted into a DataFrame in order to leverage the ... possible on the returned data. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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599 views

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scala - Spark2.1.0 incompatible Jackson versions 2.7.6

I am trying to run a simple spark example in intellij, but I get the error like that: Exception in thread "main" ... launcher_2.11" % "2.1.0" See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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587 views

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scala - Why were the case classes without a parameter list deprecated?

Why were the case classes without a parameter list deprecated from Scala? And why does compiler suggest to use () ... my second question... :| See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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805 views

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scala - How can colored terminal output be disabled for sbt/play?

I would like to disable the color escape codes logged from sbt/play. Is this possible? And if it is, ... line switch or system property. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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851 views

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scala - Unresolved dependency SBT 0.13.0 after update

Update SBT to 0.13.0: I have a couple of projects written with Scala 2.10.2 and build with sbt 0.12.4. ... this problem: sbt.version=0.13.0 See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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595 views

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scala - A grasp of immutable datastructures

I am learning scala and as a good student I try to obey all rules I found. One rule is: IMMUTABILITY!!! ... would be much easier using vars. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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616 views

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scala - How to implement implicit Json Writes of embedded object in Play Framework 2.x

there are two classes Foo and Bar. Foo contains a field of Bar. The question is, how do I implement an ... class. What is the problem here? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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725 views

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scala - Select Specific Columns from Spark DataFrame

I have loaded CSV data into a Spark DataFrame. I need to slice this dataframe into two different dataframes, ... dataframe, based on columns ? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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835 views

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scala - Scalatest - how to test println

Is there something in Scalatest that will allow me to test the output to the standard out via a println statement? ... ("hello world") } } See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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814 views

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scala - Why do case class companion objects extend FunctionN?

When you create a case class, the compiler creates a corresponding companion object with a few of the case class ... HasApply: (Int => Int) See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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753 views

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scala - The argument types of an anonymous function must be fully known. (SLS 8.5)

I have a function literal {case QualifiedType(preds, ty) => t.ty = ty ; Some((emptyEqualityConstraintSet,preds)) } Which ... (preds,ty) -> .... See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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923 views

1 answer

scala - How to reduce Seq[Either[A,B]] to Either[A,Seq[B]]?

Given a sequence of eithers Seq[Either[String,A]] with Left being an error message. I want to obtain an ... reflect the body of the message. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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600 views

1 answer

scala - mapped projection with companion object in SLICK

I have nested classes/objects and want to store (and retrieve) them in a database by using SLICK. I ... suggested solutions work for me. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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584 views

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scala - What is the difference between the methods iterator and view?

scala> (1 to 10).iterator.map{_ * 2}.toList res1: List[Int] = List(2, 4, 6, 8, 10, 12, 14 ... I choose iterator over view or view over iterator? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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591 views

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scala - How do I find out Apache Buildr/Maven 2 repo names

I'm just starting to use Apache Buildr and I'm constantly running into the problem of not knowing what repo ... for what they have available? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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603 views

1 answer

scala - Adding two columns to existing DataFrame using withColumn

I have a DataFrame with a few columns. Now I want to add two more columns to the existing DataFrame. ... or is there any alternatives? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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780 views

1 answer

scala - How to obtain the symmetric difference between two DataFrames?

In the SparkSQL 1.6 API (scala) Dataframe has functions for intersect and except, but not one for difference. ... do it, especially in Scala. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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727 views

1 answer

scala - Using Spark to write a parquet file to s3 over s3a is very slow

I'm trying to write a parquet file out to Amazon S3 using Spark 1.6.1. The small parquet that I'm ... 0 Running, 0 Completed Status: ALIVE See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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889 views

1 answer

scala - SparkSQL - Read parquet file directly

I am migrating from Impala to SparkSQL, using the following code to read a table: my_data = sqlContext.read. ... col_A, col_B from my_table' See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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