cqfd

(ns asink.core
  (:require-macros [cljs.core.async.macros :refer [go]])
  (:require [cljs.core.async :refer [<! timeout]]
            [cljs.nodejs :as n]))

(n/enable-util-print!)

(defn spin []
  (go (println "spinning...")
      (<! (timeout 1000))

cqfd

var assert = require('assert');

/*
* 1 + 2 * 3 --> 7
* Plus(1, Mult(2, 3))
*/

/*
* There are three kinds of arithmetic expressions:
*

cqfd

import scala.util.continuations._
import scala.collection.mutable

object Main {
  def main(args: Array[String]): Unit = {
    val jumpTable: mutable.Map[String, Unit => Unit] = mutable.Map()
    def label(s: String) = shift { k: (Unit => Unit) =>
      jumpTable(s) = k
      k()
    }

cqfd

require 'em-websocket'

class ChatServer
  def initialize
    @clients = []
  end
  def start!
    EM.start_server('0.0.0.0', 45678, RegularTcpConnection) do |conn|
      conn.server = self
      @clients << conn

cqfd

require 'em-http'
require 'json'

email = "eventmachinebot-bot@students.hackerschool.com"
api_key = "qHoWj0MEvawlKcj6mBly7EgFfWEu1AwJ"

class ZulipBot
  def initialize(email, api_key)
    @email = email
    @api_key = api_key

cqfd

package foo

import akka.actor.Actor
import akka.actor.Props
import akka.pattern.ask
import akka.util.Timeout
import scala.util.{Try, Success, Failure}
import scala.concurrent.{ future, Future, Promise, ExecutionContext }
import scala.concurrent.duration._

cqfd

sealed trait Arith
case class Num(n: Int) extends Arith
case class Plus(l: Arith, r: Arith) extends Arith
case class Mult(l: Arith, r: Arith) extends Arith

object Arith {
  def interp(e: Arith): Int = e match {
    case Num(n) => n
    case Plus(l, r) => interp(l) + interp(r)
    case Mult(l, r) => interp(l) * interp(r)

cqfd

board = [
  0, 0, 0,
  0, 0, 0,
  0, 0, 0
]

def print_board(board):
    print "%s | %s | %s" % (board[0], board[1], board[2])
    print "%s | %s | %s" % (board[3], board[4], board[5])
    print "%s | %s | %s" % (board[6], board[7], board[8])

cqfd

import scala.annotation.tailrec

trait PeanoNumber
case object Z extends PeanoNumber
case class S(n: PeanoNumber) extends PeanoNumber

trait BinaryTree
case object EmptyTree extends BinaryTree
case class NonEmptyTree(n: Int, l: BinaryTree, r: BinaryTree) extends BinaryTree

cqfd

1. Write a recursive function to compute the length of a list.
2. Write a recursive function to compute the sum of a list of numbers.
3. Write a recursive function to compute the sum of a binary tree of numbers.
4. Write a recursive implementation of the map function.
5. Write a recursive implementation of the filter function.
6. Write a recursive function that inserts an element in the right place into a linked list. The function should return a new linked list rather than mutate the original list.
7. The change counting problem from SICP: http://mitpress.mit.edu/sicp/full-text/sicp/book/node16.html
8. Write a recursive function that enumerates the nodes of a tree in depth-first {pre|in|post} order.
9. Write a recursive function that computes the "power set" of a set.
10. Write a recursive function that computes the number of ways of distinct k-element subsets of a set with n elements. In other words, "n choose k".