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.

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2answers
220 views

Applying Function to `Seq[B]` in `Seq[Either[A, B]]`

Given: ...
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1answer
2k views

Building a query URL in Scala

I'm working on a webapp in ScalaJS and want to create a query url for requesting some JSON. Right now I'm using a method called urlBuilder to take the query options from an Options case class and ...
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1answer
56 views

Unifying trait for tabular data in Scala

This trait is meant to be a simple interface for tabular data from different file types, such as csv, excel, open office etc. Right now I'm only asking about some of the top level code for now and ...
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1answer
4k views

Unit testing Spark transformation on DataFrame

Looking for suggestions on how to unit test a Spark transformation with ScalaTest. The test class generates a DataFrame from static data and passes it to a transformation, then makes assertion on the ...
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1answer
277 views

Game of Life in Scala with a sparse representation

While reviewing another Scala implementation of the Game of Life, I ended up drastically rewriting it. The board is represented as a Set[(Int, Int)] containing the ...
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1answer
85 views

Parsing latitude and longitude, using Try[T] to ignore errors

I wrote this question asking about how to implement my error handling while still maintaining functional code and based on 200_success's very interesting note on the spaces, I decided to ...
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1answer
370 views

Conway's Game of Life in Scala

To learn Scala, coming from Java and Python, I'm attempting to program an implementation of Conway's Game of Life. I've implemented two different approaches so far, with the first being so bad I'm ...
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2answers
510 views

Convert a String with comma separated latitudes and longitudes to a Seq[Coordinate]

I have a function that receives a String like the following: "-10.0 -10.0,10.0 10.0,0.0 0.0" And needs to translate that into ...
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2answers
654 views

Recursive Scala Case class Reduction

I have a case class that is recursive and looks like this: ...
2
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0answers
169 views

GitHub user graph crawler using akka

This code queries the GitHub followers API and stores the graph in a mongodb collection: ...
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1answer
352 views

Simple Scala money library

for some fun, I decided to start working on something that let me work with Money calculations. I realise there are libraries out there like Joda Money, but I'm doing this mainly for fun. I was ...
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1answer
534 views

Hamming distance in Scala

Problem Write a program that can calculate the Hamming difference between two DNA strands. GAGCCTACTAACGGGAT CATCGTAATGACGGCCT ^ ^ ^ ^ ^ ^^ Code ...
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1answer
711 views

Anagram in Scala

Code ...
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3answers
149 views

Nucleotide count in Scala

This is my second day in learning Scala and I still need to develop a taste of functional programming, I often find myself doing imperative coding. Below is the result of my TDD practice. Code ...
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1answer
365 views
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1answer
200 views

Little Sudoku solver

I always have enormous difficulty working out 2D grid addresses, so for me it is easier to work with the List functions. All tests pass and I'm looking for feedback ...
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1answer
400 views

Akka streams: Bidirectional flow that completes the stage when one side is completed

This is meant to be a bidirectional flow BidiFlow that works exactly as BidiFlow.identity, except that it completes the stage as soon as one of the Flows (in1 -> ...
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2answers
484 views

Rate limiter utility class

I had a problem in my system where the class that sends messages to other systems sometimes gets flooded and so I needed to add rate limiting. I threw together something that would work, but I would ...
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1answer
180 views

Implementation of API to create a company account in a database

I'm working on an API that has a lot of controller functions like this: ...
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1answer
114 views

Anagram counter

Homework prompt was: You are given two strings, a ‘parent’ string and a ‘query’ string respectively. Your task is to determine how many times the query string – or an anagram of the query string ...
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1answer
93 views

Checking whether a game board is full

I have a method in Scala that checks if a game board is full or not. To speed this method up, I return inside the nested for loop to break out of both of them and stop execution. How would I achieve ...
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0answers
193 views

Union-find implementation

Here are a few questions on my mind: What improvements to the above code can you think of? I want to say new UnionFind(x) where ...
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0answers
29 views

Getting all timeDuration from a day which are not in a list of timeDuration in Scala

I have a list of timestamp tuples of the form List((startTime,endTime)), which are basically denoting periods of time throughout the day. For example: ...
2
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1answer
45 views

Pushing data to an analytics API

This is code that handles pushing data to an analytics API, and IMO it feels too much like Java. logActivity is a method that uses ...
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0answers
199 views

Merging trees in scalaz

I just built a function to merge a set of List[A]s into a single scalaz.Tree[A]. Specifically, if I have the following three <...
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1answer
197 views

Segmented Sieve of Eratosthenes in Scala

I'm trying to solve PRIME1 in SPOJ with the following Scala snippet: Peter wants to generate some prime numbers for his cryptosystem. Help him! Your task is to generate all prime numbers between ...
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2answers
86 views

Building a Tree from Breadcrumbs

I need to transform List("home", "mens", "clothing", "jackets") into ...
2
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1answer
73 views

Print Trace Debugger

Notice: The original library has since been replaced by: https://github.com/JohnReedLOL/scala-trace-debug See my Scala print trace debugger. This project is used for lightweight debugging sort of ...
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1answer
758 views

Determining the HTTP status code to return for a request

I have a piece of code that I would like to refactor but can't figure how to do it. This is a method from a Play controller where I have to verify many precondition and respond different status for ...
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0answers
202 views

Needleman Wunsch algorithm in Scala

The Needleman–Wunsch algorithm is an algorithm used in bioinformatics to align protein or nucleotide sequences. Here is an implementation in Scala: ...
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2answers
197 views

Longest palindromes

I've been tasked to solve this exercise lately, and this is what I wrote: ...
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2answers
2k views

Limit HTTP request rate for spray/akka-http

I want to limit the request rate in a spray/akka-http route. I'm not an expert with both scala and spray/akka but learning. So I came up with the following custom directive: ...
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0answers
245 views

Finding the most frequent words in Scala using Akka

I'm new to akka and would like to get some feedback on my first attempt. The code takes text from stdin and finds the top 10 most frequently occurring words. Specifically, I would like to know Is ...
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0answers
144 views

Frequency of words in all files of a directory using Future - Scala

I created a program to get frequency of word in all files in a directory using Future API ...
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0answers
33 views

Stronger Functor TypeClass

I'm working on arrow library for scala I've come with some new typeclass, which looks like generalized Functor ...
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0answers
439 views

Immutable queue implementation in Scala

I created a queue in which we can perform Enqueue, Dequeue and Traversing in Scala. ...
3
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1answer
63 views

Implicit type class for updating maps

With the help of SO I got my code working, but I think it still could be improved, in particular I do not like using asInstanceOf. Is there some way how to avoid it?...
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1answer
3k views

List of Files in any Folder - Scala

I have written a code to count the number of files in a folder and if there are any folder inside folder it will count the files in that folder too. ...
8
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1answer
165 views

Scala implementation of @rolfl's integer-partitioning algorithm

While reviewing @Martijn's Distinct sums of integers (finding all combinations of positive integers that sum to a given number), I proposed the following solution: ...
3
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3answers
195 views

Producing uniform lists in Scala

When writing an answer to another question here, I came across the problem of producing lists of integers having a certain total and only consisting of a certain number and an optional rest. So for ...
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2answers
179 views

Functional translation of dice simulation

I have tried my hands at "functionalising" a toy problem I had: find the expected number of throws of a six sided die until all sides have been seen (the answer is 14.7) My starting point is my ...
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1answer
35 views

Similar 2 classes in Scala need to refactoring

I am newbie in scala don't know how to refactor to make it better because currently it kinds of boring when read it. I have 2 classes BidWinPostData and BidEventPostData. They are kind similar the ...
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2answers
89 views

Adding polynomials represented as maps

I'm using maps to represent a polynomial. The key is the exponent and the value is the coefficient : Map(exp -> coef) e.g. ...
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3answers
160 views

Distinct sums of integers

I need to get the distinct sums of naturals of a natural What I came up with is: ...
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0answers
402 views

collect and parallelize in spark performance

the below code is working fine, but as this is new for me, please help to improve performance. as I have not included yet my complex logic but confused over collect and parallelize. Aim is to collect ...
6
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1answer
149 views

Caching side effects

Is this a proper way to cache side effects (occurring on job.tryLoad)? ...
4
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1answer
216 views

Solution to part 1 of Day 7 Advent of Code in Scala

Does someone want to review my solution to part 1 of Day 7 Advent of Code in Scala? The assignment is here: http://adventofcode.com/day/7 Without repeating the whole text, in short: Given a text file ...
4
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1answer
586 views

Return different type of response based on Accept header

I'm a novice to Scala and Akka-Http and am experimenting with Akka-Http for writing rest services. I have to return JSON or protobuf based on the Accept-Header. ...
3
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1answer
201 views

Handling HTTP requests and saving user to database

I am using Play Framework and Slick. In userController.scala I am handling HTTP post requests and sending to personRepository.scala. Is this controller and method written in the correct way? ...
5
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0answers
691 views

RandomForest multi-class classification

Below is the code I have for a RandomForest multiclass-classification model. I am reading from a CSV file and doing various transformations as seen in the code. I ...