ceedubs’s gists

ceedubs / gist:1352742

Created November 9, 2011 19:52 — forked from hay/gist:1351230

Enterprisify your Java Class Names!

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ceedubs / FizzBuzz.scala

Created October 17, 2012 11:44

Scala FizzBuzz

	object FizzBuzz {
	val defaultRules = List(
	Rule(3, "fizz"),
	Rule(5, "buzz")
	)

	def main(args: Array[String]) = {
	fizzBuzz() foreach(println)
	}

ceedubs / zipconst.scala

Created August 4, 2013 13:36

	import shapeless._

	trait ZipConst[C, L <: HList] {
	type Out
	def apply(c: C, l: L): Out
	}

	trait ZipConstAux[C, L <: HList, O <: HList] {
	def apply(c: C, l: L): O
	}

ceedubs / gist:6934206

Last active December 25, 2015 06:39

	scala> val vs = 1.success[String] :: 2.success[String] :: Nil
	vs: List[scalaz.Validation[String,Int]] = List(Success(1), Success(2))

	scala> vs.traverseU(_.toValidationNel)
	res9: List[scalaz.Validation[scalaz.NonEmptyList[String],Int]] = List(Success(1), Success(2))

ceedubs / gist:8589661

Created January 24, 2014 00:22

Defining type alias ErrorsOrT to use liftM on EitherT instances without using a type lambda

	scala> import scalaz.syntax.id._ // for .right
	import scalaz.syntax.id._

	scala> import scalaz.EitherT
	import scalaz.EitherT

	scala> import scalaz.NonEmptyList
	import scalaz.NonEmptyList

	scala> import scala.concurrent.Future

ceedubs / gist:9345388

Created March 4, 2014 12:10

Using Scala type tags to ensure that a String is lower case. At compile time we can require a String @@ LowerCase (that is, a String that we are promising is lower case). However at runtime there is no extra boxing, so we don't have the overhead we would have if we wrapped strings in a LowerCase class.

	scala> import scalaz.{ @@, Tag }
	import scalaz.{$at$at, Tag}

	scala> sealed trait LowerCase
	defined trait LowerCase

	// as an optimization you could also define a TrustMeLowerCase method that doesn't call toLowerCase if you know your input is already lower case
	scala> def LowerCase(s: String): String @@ LowerCase = Tag[String, LowerCase](s.toLowerCase)
	LowerCase: (s: String)scalaz.@@[String,LowerCase]

ceedubs / TypeLevelFizzBuzz.scala

Last active August 29, 2015 13:58

Type level FizzBuzz

	package typelevelfizzbuzz

	import Nat._

	sealed trait Nat

	object Nat {
	sealed trait _0 extends Nat
	sealed trait Succ[T <: Nat] extends Nat
	type _1 = Succ[_0]

ceedubs / gist:cd2e11ef9b786066a8ba

Created September 30, 2014 18:49

Scalaz traverse example

	/* traverse takes an F[A] and an A => G[B] and returns a G[F[B]].
	* In this case List[Long] and Long => Option[String] result in Option[List[String]]
	*/
	scala> val usernames = Map(1L -> "susie", 2L -> "bob")
	usernames: scala.collection.immutable.Map[Long,String] = Map(1 -> susie, 2 -> bob)

	scala> List(1L, 2L).traverse(usernames.get)
	res2: Option[List[String]] = Some(List(susie, bob))

	scala> List(1L, 2L, 3L).traverse(usernames.get)

ceedubs / gist:a96bc169eb3152cd6226

Created September 30, 2014 22:17

Scalaz's Equal type class (and associated handy === syntax) is a type-safe alternative to Scala's ==

	scala> case class UserId(id: Long)
	defined class UserId

	scala> def isSusan(id: UserId): Boolean = id == 3L // see the bug?
	isSusan: (id: UserId)Boolean

	scala> isSusan(UserId(3L))
	res31: Boolean = false// shouldn't this be true?

	// let's show the compiler how to check whether two UserIds are equal

ceedubs / gist:f8273ede78f86df7df7f

Last active August 29, 2015 14:07

Turning List[Int => Int] into Int => List[Int] with sequenceU

	import scalaz.std.list._
	import scalaz.std.function._
	import scalaz.syntax.traverse._

	val add1: Int => Int = _ + 1
	val times2: Int => Int = _ * 2
	val squared: Int => Int = n => n * n
	// sequenceU requires that List has a Traverse instance
	// and that Function1 (for Int => Int in this case) has an Applicative instance
	// luckily, scalaz provides both

Cody Allen ceedubs