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Scalaz: one symbol at a time (OSAAT#1)

Symbol

|> or ▹

Pronounced

• Pipe
• The Thrush combinator

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scalaz (series/7.2.x)$ grep -R 'def [^A-Za-z_]' core effect concurrent iteratee
core/src/main/scala/scalaz/Arrow.scala:  final def <<<[A, B, C](fbc: (B =>: C), fab: (A =>: B)): =>:[A, C] =
core/src/main/scala/scalaz/Arrow.scala:  def >>>[A, B, C](fab: (A =>: B), fbc: (B =>: C)): (A =>: C) =
core/src/main/scala/scalaz/BijectionT.scala:  def ***[C, D](g: Bijection[C, D])(implicit evF: F[B] =:= Id[B], evG: G[A] =:= Id[A]): Bijection[(A, C), (B, D)] =
core/src/main/scala/scalaz/BijectionT.scala:  def ^^^[C, D](g: Bijection[C, D])(implicit evF: F[B] =:= Id[B], evG: G[A] =:= Id[A]): Bijection[A \/ C, B \/ D] =
core/src/main/scala/scalaz/BijectionT.scala:  def <=<[C](that: BijectionT[F, G, C, A])(implicit FM: Bind[F], GM: Bind[G]): BijectionT[F, G, C, B] = compose(that)
core/src/main/scala/scalaz/BijectionT.scala:  def >=>[C](that: BijectionT[F, G, B, C])(implicit M: Bind[F], GM: Bind[G]): BijectionT[F, G, A, C] = andThen(that)
core/src/main/scala/scalaz/Cofree.scala:  final def =>>[B](f: Cofree[S, A] => B)(implicit

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implicit val pc = PopulationControl(
  dataSource=postgressDs,
  ...customzation here)

"Friends database" should {

  populate("""

    # User

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scala> :paste
// Entering paste mode (ctrl-D to finish)

object Colours extends Enumeration {
  val Red, Amber, Green = Value
}

object WeekDays extends Enumeration {
  val Mon,Tue,Wed,Thu,Fri = Value
}

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scala> :paste
// Entering paste mode (ctrl-D to finish)

def traffic(colour: Colours.Value) = colour match {
 case Colours.Green => "Go"
}

// Exiting paste mode, now interpreting.

traffic: (colour: Colours.Value)String

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object WeekDay {
  sealed trait EnumVal
  case object Mon extends EnumVal
  case object Tue extends EnumVal
  case object Wed extends EnumVal
  case object Thu extends EnumVal
  case object Fri extends EnumVal
  val daysOfWeek = Seq(Mon, Tue, Wed, Thu, Fri)
}

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object SolarSystemPlanets {

  sealed abstract class Planet(
    val orderFromSun : Int,
    val name         : String,
    val mass         : Kilogram,
    val radius       : Meter) extends Ordered[Planet] {

      def compare(that: Planet) = this.orderFromSun - that.orderFromSun

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scala> import SolarSystemPlanets._
import SolarSystemPlanets._

scala> println(planets)
TreeSet(Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune)

scala> EARTH < MARS
res1: Boolean = true

scala> planets.filter(_.radius > 7.0e6)

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package code.filter

import javax.servlet._
import http._
import java.util.regex._

// A wrapper around an HTTP Servlet Request which removes any /cached/:id from a URI
case class ResouceRequest(req: HttpServletRequest) extends HttpServletRequestWrapper(req) {

  // The URI without the /cached/:id part:

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import play.api.libs.json._
case class Notify(email: Option[String] = None)
implicit val reader = Json.reads[Notify]

Json.parse(""" { "email": "[email protected]" } """).asOpt[Notify]
// res0: Option[Notify] = Some(Notify(Some([email protected])))

Json.parse(""" { } """).asOpt[Notify]
// res1: Option[Notify] = Some(Notify(None))