Here's an ADT which is not a GADT, in Haskell:
data Expr = IntExpr Int | BoolExpr Bool
import cats.Traverse | |
import cats.effect._ | |
import cats.effect.concurrent.Semaphore | |
import cats.temp.par._ | |
import cats.syntax.all._ | |
import scala.concurrent.duration._ | |
object Main extends IOApp { | |
import ParTask._ |
Tageless Final interpreters are an alternative to the traditional Algebraic Data Type (and generalized ADT) based implementation of the interpreter pattern. This document presents the Tageless Final approach with Scala, and shows how Dotty with it's recently added implicits functions makes the approach even more appealing. All examples are direct translations of their Haskell version presented in the Typed Tagless Final Interpreters: Lecture Notes (section 2).
The interpreter pattern has recently received a lot of attention in the Scala community. A lot of efforts have been invested in trying to address the biggest shortcomings of ADT/GADT based solutions: extensibility. One can first look at cats' Inject
typeclass for an implementation of [Data Type à la Carte](http://www.cs.ru.nl/~W.Swierstra/Publications/DataTypesA
This describes how I setup Atom for an ideal Clojure development workflow. This fixes indentation on newlines, handles parentheses, etc. The keybinding settings for enter (in keymap.cson) are important to get proper newlines with indentation at the right level. There are other helpers in init.coffee and keymap.cson that are useful for cutting, copying, pasting, deleting, and indenting Lisp expressions.
The Atom documentation is excellent. It's highly worth reading the flight manual.
// WARNING! totally untested, I have only compiled the code! :) | |
package json | |
import collection.immutable.Map | |
import scalaz.{\/, MonadPlus} | |
import scalaz.\/._ | |
import scalaz.std.vector._ | |
import scalaz.std.map._ | |
import scalaz.std.list._ |
Miles Sabin recently opened a pull request fixing the infamous SI-2712. First off, this is remarkable and, if merged, will make everyone's life enormously easier. This is a bug that a lot of people hit often without even realizing it, and they just assume that either they did something wrong or the compiler is broken in some weird way. It is especially common for users of scalaz or cats.
But that's not what I wanted to write about. What I want to write about is the exact semantics of Miles's fix, because it does impose some very specific assumptions about the way that type constructors work, and understanding those assumptions is the key to getting the most of it his fix.
For starters, here is the sort of thing that SI-2712 affects:
def foo[F[_], A](fa: F[A]): String = fa.toString
Use a git hook to match a Jira issue ID from the current branch, and prepend it to every commit message
Assuming the current branch contains a Jira issue ID, you can use a git hook script to prepend it to every commit message.
Create an empty commit-msg git hook file, and make it executable. From your project's root directory:
install -b -m 755 /dev/null .git/hooks/commit-msg
Save the following script to the newly-created .git/hooks/commit-msg file: