halcat0x15a

Pipeモナドの紹介

Scalaの記事です。Haskellはあまり書けません。

Iterateeの複雑さから開放されたいのでPipe系ライブラリ使いましょうという記事です。

Iterateeとの比較や簡単な使い方についてつらつらと書いていきます。

Iterateeについて

gakuzzzz

package disample

case class DiSampleConfig(foo: Int, bar: String)
object DiSampleConfig {
  implicit val configs: Configs[DiSampleConfig] = Configs { c =>
    DiSampleConfig(
      foo = c.get[Int]("foo"),
      bar = c.get[String]("bar")
    )
  }

xeno-by

import scala.annotation.StaticAnnotation
import scala.reflect.macros.Macro
import language.experimental.macros

class body(tree: Any) extends StaticAnnotation

trait Macros extends Macro {
  import c.universe._

  def selFieldImpl = {

puffnfresh

var daggy = require('daggy'),
    State = require('fantasy-states'),
    Cofree = require('fantasy-cofrees'),
    AST = daggy.taggedSum({
        Add: ['l', 'r'],
        Sub: ['l', 'r'],
        Num: ['n']
    }),
    incNode = State.get.chain(function(n) {
        return discard(

xuwei-k

class A(private[this] var a: => Int){
  lazy val b = a
}

puffnfresh

var State = require('fantasy-states'),
    Tuple2 = require('fantasy-tuples').Tuple2,
    
    // Tuple2 Number Number
    initial = Tuple2(0, 1),
    
    // State (Tuple2 Number Number) Number -> State (Tuple2 Number Number) Number
    next = discard(
      	State.modify(function(t) {
            return Tuple2(t._1 + 1, (t._1 + 1) * t._2);

halcat0x15a

import scalaz._, Scalaz._

object MaxValue extends App {

  val a = Map(1 -> 10, 2 -> 5)
  val b = Map(2 -> 10, 3 -> 7)
  val c = a.mapValues(Tags.MaxVal) |+| b.mapValues(Tags.MaxVal)
  (c: Map[Int, Int]) assert_=== Map(1 -> 10, 2 -> 10, 3 -> 7)

}

tototoshi

val m1 = Map(1 -> 2, 2 -> 5, 3 -> 1)
val m2 = Map(2 -> 4, 3 -> 3, 4 -> 3)

def toMultiMap[A, B](m1: Map[A, B], m2: Map[A, B]): Map[A, Set[B]] = 
  (m1.toSeq ++ m2.toSeq).groupBy(_._1).mapValues(_.map(_._2).toSet)

/*
scala> toMultiMap(m1, m2).mapValues(_.max)
res0: scala.collection.immutable.Map[Int,Int] = Map(2 -> 5, 4 -> 3, 1 -> 2, 3 -> 3)
*/

xuwei-k

collection

each(list, iterator, [context]forEachforeach

underscore	Scala

gist:5685201

import Data.Semigroup
import Numeric.Natural.Internal

-- 2x2 integer matrix [[a,b],[c,d]]
data Mat2x2 a = Mat2x2 a a a a deriving (Show,Eq)

-- multiply matrix [[a,b],[c,d]] . [[p,q],[r,s]] = [[a*p+b*r, a*q+b*s],[c*p+d*r, c*q+d*s]]
multiply_mat2x2 :: Num a => Mat2x2 a -> Mat2x2 a -> Mat2x2 a
multiply_mat2x2 (Mat2x2 a b c d) (Mat2x2 p q r s) = Mat2x2 (a*p+b*r) (a*q+b*s) (c*p+d*r) (c*q+d*s)