gvolpe

Dependency Injection in Functional Programming

There exist several DI frameworks / libraries in the Scala ecosystem. But the more functional code you write the more you'll realize there's no need to use any of them.

A few of the most claimed benefits are the following:

• Dependency Injection.
• Life cycle management.
• Dependency graph rewriting.

non

introduction

ScalaCheck 1.14.0 was just released with support for deterministic testing using seeds. Some folks have asked for examples, so I wanted to produce a Gist to help people use this feature.

simple example

These examples will assume the following imports:

SteefH

Amorphous: Writing a Scala library for boilerplate-free object mapping

At Infi, we started our first Scala project (link in Dutch) in mid-2016. When it became clear that Scala might be one of the technologies used in the project, I jumped at the chance to be part of it, because I'm always eager to learn new tech, and doing a project in a functional programming language was already near the top of my professional wish list.

As always when learning new technology, I like to push the envelope to see where things start to break down. I think that's a nice way to get to know the limits of that technology. As it turns out, Scala is a powerful language, with a strong type system that lets you use many advanced concepts I won't detail here (eg. type classes, high-level abstractions like the ones in the Typeclassopedia with the help of scalaz or [Cats](https://github.com

micahgodbolt

The apt-get version of node is incredibly old, and installing a new copy is a bit of a runaround.

So here's how you can use NVM to quickly get a fresh copy of Node on your new Bash on Windows install

$ touch ~/.bashrc
$ curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.35.3/install.sh | bash
// restart bash
$ nvm install --lts

dusenberrymw

Spark Tips & Tricks

Misc. Tips & Tricks

• If values are integers in [0, 255], Parquet will automatically compress to use 1 byte unsigned integers, thus decreasing the size of saved DataFrame by a factor of 8.
• Partition DataFrames to have evenly-distributed, ~128MB partition sizes (empirical finding). Always err on the higher side w.r.t. number of partitions.
• Pay particular attention to the number of partitions when using flatMap, especially if the following operation will result in high memory usage. The flatMap op usually results in a DataFrame with a [much] larger number of rows, yet the number of partitions will remain the same. Thus, if a subsequent op causes a large expansion of memory usage (i.e. converting a DataFrame of indices to a DataFrame of large Vectors), the memory usage per partition may become too high. In this case, it is beneficial to repartition the output of flatMap to a number of partitions that will safely allow for appropriate partition memory sizes, based upon the

jdegoes

Applied Functional Programming with Scala - Notes

Copyright © 2016-2018 Fantasyland Institute of Learning. All rights reserved.

1. Mastering Functions

A function is a mapping from one set, called a domain, to another set, called the codomain. A function associates every element in the domain with exactly one element in the codomain. In Scala, both domain and codomain are types.

val square : Int => Int = x => x * x

remarkablemark

# set the base image to Debian
# https://hub.docker.com/_/debian/
FROM debian:latest

# replace shell with bash so we can source files
RUN rm /bin/sh && ln -s /bin/bash /bin/sh

# update the repository sources list
# and install dependencies
RUN apt-get update \

jkpl

object Main extends App {
  AvoidLosingGenericType.run()
  AvoidMatchingOnGenericTypeParams.run()
  TypeableExample.run()
  TypeTagExample.run()
}

class Funky[A, B](val foo: A, val bar: B) {
  override def toString: String = s"Funky($foo, $bar)"
}

etorreborre

import scala.collection.mutable.ListBuffer
import org.scalacheck._, Arbitrary._, Prop._
  
// a specs2 example showing that it works  
def e1 =
  forAll(distinctListOf[Int]) { ls =>
    ls.distinct === ls
  }.set(minTestsOk = 10000, maxSize = 1000)
  
// distinct list of elements from a given arbitrary

rjsen

import scala.annotation.{StaticAnnotation, compileTimeOnly}
import scala.language.experimental.macros
import scala.reflect.macros.whitebox.Context

@compileTimeOnly("use macro paradise")
class Extends[T](defaults: Any*) extends StaticAnnotation {
  def macroTransform(annottees: Any*): Any = macro Extends.impl
}

object Extends {