tpolecat

Latest releases and supported Scala versions for org.tpolecat stuff

	Release	2.12	2.13	3.0.0	Notes
Atto	0.9.5	✅	✅	✅
Doobie (CE2)	0.13.4	✅	✅	✅
Doobie (CE3)	1.0.0-M5	✅	✅	✅
Natchez (CE2)	0.0.26	✅	✅	✅	EOL
Natchez (CE3)	0.1.3	✅	✅	✅

tpolecat

Vaccine waiting lists in/around Austin

Let me know if you hear of any more and I'll update the list.

Hub/Provider	Registration URL
Bastrop	www.covac.info
Bell	http://www.bellcountyhealth.org
Gillespie	https://www.hillcountrymemorial.org/hill-country-covid/

tpolecat

import java.io.ByteArrayInputStream
import java.security.PrivateKey
import java.security.PublicKey
import org.bouncycastle.jce.provider.BouncyCastleProvider
import org.bouncycastle.openpgp.operator.jcajce._
import org.bouncycastle.openpgp._
import scala.util.control.NonFatal

/**
 * Methods to turn GPG ASCII-amored exported text into JCA keys. Many thanks to Twitter friends, 

tpolecat

Ok, so to map CITEXT, which is not a standard type JDBC knows about, we need a wrapper class and need to move the value back and forth via the generic PGobject data type.

import org.postgresql.util.PGobject

case class CIText(s: String)

object CIText {
 

tpolecat

sealed trait MaybeNumeric[A]
case class  YesNumeric[A](n: Numeric[A]) extends MaybeNumeric[A]
case class  NoNumeric[A]() extends MaybeNumeric[A]

object MaybeNumeric {
  implicit def instance[A](implicit ev: Numeric[A]): MaybeNumeric[A] =
    YesNumeric(ev)
}

tpolecat

import scalaz._, Scalaz._

/** Abstraction over functions of the shape `A => F[A]`. */
case class EndoT[F[_], A](run: A => F[A]) {

  def apply(a: A): F[A] =
    run(a)

  def andThen(e: EndoT[F, A])(implicit ev: Bind[F]): EndoT[F, A] =
    e.compose(this)

tpolecat

It's not good enough to abstract Future to M[_]: Monad

Let's get our imports out of the way.

import scala.util.Random.nextInt
import scala.concurrent._
import scala.concurrent.duration._
import scala.concurrent.ExecutionContext.Implicits.global

tpolecat

// addCompilerPlugin("com.milessabin" % "si2712fix-plugin" % "1.2.0" cross CrossVersion.full)
import scalaz._, Scalaz._

implicit def f2k[F[_], A, B](f: A => F[B]) = Kleisli(f)

val a: Int => ListT[List, Int] = {
  case 0 => ListT(List(List(0, 1)))
  case 1 => ListT(List(List(0), List(1)))
}

tpolecat

EDIT: This gist has been promoted and is now a blog post.

Kinda-Curried Type Parameters

Scala methods can have multiple lists of value parameters but only one list of type parameters, which is occasionally irritating when some are inferable and others are not. Consider this method which has two type parameters, one inferable and one not.

import scalaz._, Scalaz._

tpolecat

doobie experiment - postgres NOTIFY as scalaz-stream

One of the cool things PostgreSQL gives you is a simple notification system that you can use to let clients know that something interesting has happened. For instance you can set up rules that broadcast notifications when a table is updated, and client applications can update displays in response. The JDBC driver provides access to this API so I thought I would see what it would look like in doobie.

The program below constructs a Process[ConnectionIO, PGNotification] that registers for events, polls for them periodically (this is the best we can do with current driver support), and unregisters when the stream terminates for any reason. We use a Transactor to replace ConnectionIO with Task which gives us something we can actually run.

package doobie.example

import doobie.imports._