ppurang

/*
Given a map defined like:

def map[A, B](f: A => B)(btree: BTree[A]): BTree[B] =
    fold((_:A) => Leaf(f(_)).asInstanceOf[BTree[B]])((x:BTree[B]) => (y:BTree[B]) => Fork(x,y))(btree)

when applied on a tree ((1 2) (3 4))
 map((x:Int) => x*2)(BTree(1 :: 2 :: 3 :: 4 :: Nil)) 

results in ((<function1> <function1>) (<function1> <function1>)) 

ppurang

scala> trait YouCantMatchMe
defined trait YouCantMatchMe

scala> object YesICan extends Traitor[YouCantMatchMe]
defined module YesICan

scala> def uncatchable_?(any: Any) = any match {
     |   case YesICan(uncatchable) => Some(uncatchable)
     |   case _ => None
     | }

ppurang

quicksort

scala

def qsort[A <% Ordered[A]](v: Seq[A]): Seq[A] = v.headOption match {
  case Some(x) => (qsort(v.tail.filter(_ < x)) :+ x) ++ qsort(v.tail.filter(_ >= x))
  case _ => Seq()
}

haskell

ppurang

//performance is not everything 
//can this be parallel?

def isPalindrome(list: List[Int]) = {
  (list zip list.reverse filter (a => a._1 != a._2) size) == 0
}

ppurang

import sbt._
import Keys._
import sbt.Package._
import java.util.jar.Attributes.Name._
import com.github.siasia.WebPlugin._

//unashamed copy of scalaz's build
object SlogBuild extends Build {

  override lazy val settings = super.settings :+

ppurang

#!/bin/sh
L=`dirname $0`/../lib
cp=`echo $L/*.jar|sed 's/ /:/g'`
exec scala -classpath $cp -savecompiled $0 $@ 
!#

# shebang magic from  http://www.eamonn.org/blog/archives/425
println("hello world")

ppurang

-- import Control.Monad (ap)
type Pos = (Int, Int)
type Direction = Pos -> Pos

direction :: Pos -> [Direction] -> [Pos]
direction p [] = []
direction p (x:xs) = x p : direction p xs
-- another way
-- direction p ds = ap ds [p] 

ppurang

val add = """.*: what is (\d*) plus (\d*)""".r

q match {

  case add(a, b) =>(a.toInt + b.toInt).toString
  case bond() => // well we don't want to reveal too much
  case banana() => //but bond and banana ought to get the attention.
  case _ => ""
}

ppurang

Type Class

Origin

http://homepages.inf.ed.ac.uk/wadler/papers/class/class.ps

Haskell

http://www.haskell.org/haskellwiki/Typeclassopedia

ppurang

:silent

//the following are helper functions

def p = if(readLine() == "q") sys.exit 
def pp[A]: ( => A) => Unit = a => {readLine() ; a} 
object > { 
  def > : String => Unit = println _
  def >[A] : (String,  => A) => Unit = (a,b) => {print("> " + a); readLine(); readLine(); println("  ---->  " + b); println}   
}