jashkenas

Spurred by recent events (https://news.ycombinator.com/item?id=8244700), this is a quick set of jotted-down thoughts about the state of "Semantic" Versioning, and why we should be fighting the good fight against it.

For a long time in the history of software, version numbers indicated the relative progress and change in a given piece of software. A major release (1.x.x) was major, a minor release (x.1.x) was minor, and a patch release was just a small patch. You could evaluate a given piece of software by name + version, and get a feeling for how far away version 2.0.1 was from version 2.8.0.

But Semantic Versioning (henceforth, SemVer), as specified at http://semver.org/, changes this to prioritize a mechanistic understanding of a codebase over a human one. Any "breaking" change to the software must be accompanied with a new major version number. It's alright for robots, but bad for us.

SemVer tries to compress a huge amount of information — the nature of the change, the percentage of users that wil

eevee

HEY: I've turned this into a blog post, which is a little more in depth.

🚨 https://eev.ee/blog/2016/06/04/converting-a-git-repo-from-tabs-to-spaces/ 🚨

---

Death to tabs, long live spaces

Do this

milessabin

import shapeless._

sealed trait List[+T]
case class Cons[T](hd: T, tl: List[T]) extends List[T]
sealed trait Nil extends List[Nothing]
case object Nil extends Nil

trait Show[T] {
  def apply(t: T): String
}

milessabin

scala> import shapeless._, syntax.singleton._, record._
import shapeless._
import syntax.singleton._
import record._

scala> object ->> {
     |   def unapply[K, V](f: FieldType[K, V])(implicit k: Witness.Aux[K]) = Option((k.value, f: V))
     | }
defined module $minus$greater$greater

milessabin

scala> import shapeless._; import SingletonTypes._; import Record._
import shapeless._
import SingletonTypes._
import Record._

scala> val r = ("foo" ->> 23) :: ("bar" ->> true) :: ("baz" ->> 2.0) :: HNil
r: (String("foo"), Int) :: (String("bar"), Boolean) :: (String("baz"), Double) :: HNil =
   (foo,23) :: (bar,true) :: (baz,2.0) :: HNil

scala> r.head         // r is an HList of pairs of singleton-typed Strings and values ...

fanf

package test_shapeless

object DI {
  import shapeless._

  trait Injecter[L <: HList, A] {
    def apply(l: L) : A
  }

  trait InjecterAux[L <: HList, A] {

paulp

/* A better way to tag types?
 *
 * 1) object Time: here we are distinguishing between different uses of a Long,
 * yet there is no boxing whatsoever.
 *
 *   main calls start: ()J
 *   main calls timed: (Function0, J)
 *   Function0 gives up the result: ()J
 *   timed calls now: ()J
 *   timed calls elapsed$extension: (JJ)J

travisbrown

scala> import scala.language.experimental.macros
import scala.language.experimental.macros

scala> import scala.reflect.macros.{ Context, TypecheckException }
import scala.reflect.macros.{Context, TypecheckException}

scala> object NoncompilationTests {
     |   def compiles(code: _): Boolean = macro compiles_impl
     |   def compiles_impl(c: Context)(code: c.Tree) = c.literal(
     |     try {

julienrf

object Ok {
  trait Foo[A]
  case class Bar(x: Int)
  object Bar {
    implicit class BarOps(bar: Foo[Bar]) {
      val ok = "ok"
    }
  }

  def usage(bar: Foo[Bar]) = bar.ok // Ok, the implicit conversion is found in the Bar companion object

paulp

/** Constructing "singleton types" from compile-time literals
  *
  * val x = Example.foo(42)
  * val y: x.T = 42 // compiles
  * val z: x.T = 43 // doesn't
  *
  */
package s

import scala.language.experimental.macros