tpolecat

Hi, looking for scalac flags?

This gist has been upgraded to a blog post here.

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

  implicit def treeEncode[A: EncodeJson]: EncodeJson[Tree[A]] =
    EncodeJson(t => (t.rootLabel, t.subForest).asJson)

  implicit def treeDecode[A: DecodeJson]: DecodeJson[Tree[A]] =
    DecodeJson(c =>
      for {
        rootLabel <- (c =\ 0).as[A]
        subForest <- (c =\ 1).as[Stream[Tree[A]]]
      } yield Tree.node(rootLabel, subForest)

tpolecat

> runMain doobie.hi.Test
[info] Compiling 37 Scala sources to /Users/rnorris/Scala/doobie/target/scala-2.10/classes...
[info] Running doobie.hi.Test 
The answer was: java.lang.RuntimeException: Bogus country: NCL

  nyQL log for hi.examples
  +- [ok] getConnection(jdbc:h2:mem:test;DB_CLOSE_DELAY=-1, sa, ***)      |  conn1: url=jdbc:h2:mem:test us   304.109 ms
  `- [ex] database session                                                |  Bogus country: NCL              1496.911 ms
     +- [ok] populate database from /Users/rnorris/Scala/doobie/world.sql |  false                           1378.663 ms
     |  +- [ok] prepareStatement(RUNSCRIPT FROM ? CHARSET 'UTF-8')        |  prep1: RUNSCRIPT FROM ? CHARSE     3.950 ms

tpolecat

scala> class Foo(val n: Int)
defined class Foo

scala> class Bar(n: Int) extends Foo(n)
defined class Bar

scala> List[Foo]().sorted
<console>:9: error: No implicit Ordering defined for Foo.
              List[Foo]().sorted
                          ^

tpolecat

package spire.examples

import spire.algebra._
import spire.math.{Natural, UInt}

import scala.collection.mutable

object SetUtil {
  def powerStream[A](members: Stream[A]): Stream[Set[A]] = {
    val done = Stream.empty[Set[A]]

tpolecat

import shapeless._

// typeclass for total number of fields (just an example)
class Width[A](val toInt: Int)

object Width {

  // Get an instance
  implicit def apply[A](implicit A: Width[A]) = A

tpolecat

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

def subsets[A](as: List[A]): List[List[A]] = {
  def sub0(accum: List[List[A]], as: List[A]): List[List[A]] = 
    as match {
      case Nil => accum
      case a :: as => sub0(accum ++ accum.map(a :: _), as)
    }
  sub0(List(Nil), as)

tpolecat

// Where the hell does B come from? Looks like a type variable is escaping.

scala> Left(1).disjunction
res14: scalaz.\/[Int,B] = -\/(1)

// It's not Nothing

scala> Left(1).disjunction : (Int \/ Nothing)
<console>:17: error: type mismatch;
 found   : scalaz.\/[Int,B]

tpolecat

name := "just-scalaz"

version := "0.1"

scalaVersion := "2.10.2"

libraryDependencies ++= Seq(
  "org.scalaz" % "scalaz-core_2.10" % "7.0.3",
  "org.scalaz" % "scalaz-effect_2.10" % "7.0.3"
)