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vpatryshev / EnvHacker.scala
Last active August 4, 2021 12:29 — forked from jaytaylor/EnvHacker.scala
Setting environment variables in Scala JVM
import java.util.{Collections, Map => JavaMap}
import scala.collection.JavaConverters._
trait EnvHacker {
/**
* Portable method for setting env vars on both *nix and Windows.
* @see http://stackoverflow.com/a/7201825/293064
*/
def setEnv(newEnv: Map[String, String]): Unit = {
try {
@vpatryshev
vpatryshev / CovarianceAndContravariance.scala
Last active August 24, 2021 03:15
## Covariance and Contravariance Illustrated
import Experiments_1.Q2
object Experiments_1:
// class Q1[+T]:
// def enqueue(x: T): Unit = println(s"Q1 enqueued $x")
// val x1: Q1[Any] = new Q1[Int]
class Q2[-T]:
def enqueue(x: T): Unit = println(s"Q2 enqueued $x")
@vpatryshev
vpatryshev / ImplicitConverter.scala
Created January 31, 2022 13:08
How to build an implicit generic converter
class Test extends AnyFlatSpec with Matchers {
"transformer" should "work" in {
// source: https://contributors.scala-lang.org/t/ability-to-force-the-caller-to-specify-a-type-parameter-for-a-polymorphic-method/2116/26
sealed trait NotNothing[-T]
object NotNothing {
@implicitAmbiguous("inst() method needs a generic parameter type, which is missing")
implicit val nothingIsNothing = new NotNothing[Nothing]{}
implicit def notNothing[T] = new NotNothing[T] {}
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vpatryshev / NotaMonad.scala
Created November 13, 2022 17:33
sample applicative functor in Scala that is not a monad
/**
* An example of a polynomial applicative functor `1+X×X` build from two monads, 1+ and X×X, and
* which is not a monad.
*
* Idea: https://stackoverflow.com/questions/49742377/is-data-poe-a-empty-pair-a-a-a-monad/49742857#49742857
*/
object NotMonad {
sealed trait SquarePlusOne[+A] {
def map[B](f: A => B): SquarePlusOne[B]
}
@vpatryshev
vpatryshev / findjdks.sh
Created January 17, 2024 19:44
Find JDKs that will work with your Scala project
#!/bin/bash
Try all available JDKs to find which one works for your Scala and sbt.
clear && printf '\e[3J'
function testWith(){
java=$1
echo Y | sdk install java "$java"
sdk use java "$java"
sbt clean test package 2>$java.log && rm $java.log && return 0 || return 1