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ceedubs / gist:1352742
Created November 9, 2011 19:52 — forked from hay/gist:1351230
Enterprisify your Java Class Names!
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<title></title>
<style>
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background: white;
text-align: center;
padding: 20px;
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@ceedubs
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
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
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
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
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
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
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
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
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