davidallsopp

#
# A crude demo of how IO can be pure yet achieve something.
# All functions are pure, including main(). Only __main__ has effects.
#
class IO:
    def __init__(self, f):
        self.f = f
    
    def run(self, x):
        return self.f(x)

davidallsopp

object GeoHash {

  import Base32._, Calation._

  val LAT_RANGE = (-90.0, 90.0)
  val LON_RANGE = (-180.0, 180.0)

  // Aliases, utility functions
  type Bounds = (Double, Double)
  def mid(b: Bounds) = (b._1 + b._2) / 2.0

davidallsopp

/**
 * Examples of writing mixed unit/property-based (ScalaCheck) tests.
 *
 * Includes tables and generators as well as 'traditional' tests.
 *
 * @see http://www.scalatest.org/user_guide/selecting_a_style
 * @see http://www.scalatest.org/user_guide/property_based_testing
 */

import org.scalatest._

davidallsopp

import org.scalatest._
import prop._
import org.scalacheck.Arbitrary._
import org.scalacheck.Gen

/**
 * Solutions to the ScalaCheck problem that shrinking failing values may generate 
 * invalid values, because the constraints of the generator are not respected.
 *
 * See also http://stackoverflow.com/questions/20037900/scalacheck-wont-properly-report-the-failing-case

davidallsopp

// An explanation of using the Option type in Scala rather than null (in languages such as Java)
// The equivalent in Haskell is the Maybe type

// The Option type is for values that might or might not exist - i.e. exactly the use case
// that null fulfills. It has two subtypes: Some[A] and None
// ( where A is a type parameter - i.e. Some is a generic type. )

val yes = Some("Hello world!")
val no = None

davidallsopp

import scala.language.implicitConversions

object configs {

  // Options (e.g. from a config file or system properties), as key-value strings
  val opts = Map("min" -> "100", "path" -> "/home/user2")

  // Automatically wrap the default values in a Some 
  // (or can omit this and specify None to indicate lack of a default value)
  implicit def wrap[A](a: A) = Some(a) 

davidallsopp

package example

import java.util.Date

object NoNulls {

  sealed trait Employee // sealed, so nobody else can create further subclasses
  object Employee {
  
    def apply(id: Int, name: String, start: Date=new Date()) = CurrentEmployee(id, name, start) // factory method

davidallsopp

import random
import sys

while True:
  for i in range(80):
    sys.stdout.write(random.choice("\/|-"))
  print

davidallsopp

import random
from random import randint
from winsound import Beep

while True:
    Beep(randint(200,5000), 250)

davidallsopp

letters = 'abcdefghijklmnopqrstuvwxyz '
jumbled = 'jklmnopqrstuvwxyzabcdefghi '

# Long way
#decrypt_map = { }
#encrypt_map = { }
#for x in range(len(encrypted_letters)):
#    encrypted_letter = encrypted_letters[x]
#    unencrypted_letter = unencrypted_letters[x]
#    decrypt_map[unencrypted_letter] = encrypted_letter