Getting Functional with Scala

Getting Functional with Scala

• 1.
  Getting Functional withScala An Introduction to Functional Programming and the Scala Programming Language September, 2016
• 2.
  2 Software Engineer atIBM Mobile Innovation Lab @jorgelpaez19 Jorge Paez
• 3.
  3 My IBM Journey…So far www-01.ibm.com/employment/us/extremeblue https://www.ibm.com/innovation/milab/
• 4.
  4 Where will yoursstart? http://www-03.ibm.com/employment/entrylevel_campus.html
• 5.
  5 What is FunctionalProgramming?
• 6.
  6 Function Not aFunction
• 7.
  7 Core Ideas • Datais immutable • PURE function are our basic building block • Use expressions over instructions • First class functions • Type-strictness
• 8.
  8 …but why?
• 9.
  9 Benefits! • Simpler concurrency/parallelism •Optimizations with caching or memoization • Easier debugging • Cleaner/less verbose code • Encourages code re-use • Promotes Test Driven Development
• 10.
  10 Pure vs Impure //In Main.java public String getFormal(String name) {
 name = "Mr." + name;
 return name;
 } // In Main.scala def getFormal(name: String) = s"Mr. $name!"
• 11.
  11 Expressions vs Instructions //In Main.java public double[] convertToMeters(double[] measurements) {
 double[] metricMeasurements = 
 new double[measurements.length];
 
 for(int i = 0; i < measurements.length; ++i) {
 metricMeasurements[i] =
 measurements[i] * CONVERSION_FACTOR;
 }
 
 return metricMeasurements;
 } // In Main.scala def convertToMeters(measurements: Seq[Double]) =
 measurements.map(n => n * CONVERSION_FACTOR)
• 12.
  12 First Class Functions defmain(args: Array[String]): Unit = {
 draw(getCurve(0, 90), 1)
 draw(getCurve, 2)
 }
 
 def getCurve: Double => Seq[(Double, Double)] =
 (r) => (0 to 360).map(theta => getCartesianCoordinates(r, theta))
 
 def getCurve(thetaO: Int, thetaF: Int): Double => Seq[(Double, Double)] =
 (r) => (thetaO to thetaF).map(theta => getCartesianCoordinates(r, theta))
 
 def getCartesianCoordinates(r: Double, theta: Double): (Double, Double) =
 ((r * Math.cos(theta)), (r * Math.sin(theta)))
 
 
 def draw(func: Double => Seq[(Double, Double)], scale: Double)
• 13.
  13 First Class Functions defmain(args: Array[String]): Unit = {
 draw(getCurve(0, 90), 1)
 draw(getCurve, 2)
 }
 
 def getCurve: Double => Seq[(Double, Double)] =
 (r) => (0 to 360).map(theta => getCartesianCoordinates(r, theta))
 
 def getCurve(thetaO: Int, thetaF: Int): Double => Seq[(Double, Double)] =
 (r) => (thetaO to thetaF).map(theta => getCartesianCoordinates(r, theta))
 
 def getCartesianCoordinates(r: Double, theta: Double): (Double, Double) =
 ((r * Math.cos(theta)), (r * Math.sin(theta)))
 
 
 def draw(func: Double => Seq[(Double, Double)], scale: Double) 
 
 def getCurve: Double => Seq[(Double, Double)] =
 (r) => (0 to 360).map(theta => getCartesianCoordinates(r, theta))
 
 def getCurve(thetaO: Int, thetaF: Int): Double => Seq[(Double, Double)] =
 (r) => (thetaO to thetaF).map(theta => getCartesianCoordinates(r, theta))
 
 
 

• 14.
  14 First Class Functions defmain(args: Array[String]): Unit = {
 draw(getCurve(0, 90), 1)
 draw(getCurve, 2)
 }
 
 def getCurve: Double => Seq[(Double, Double)] =
 (r) => (0 to 360).map(theta => getCartesianCoordinates(r, theta))
 
 def getCurve(thetaO: Int, thetaF: Int): Double => Seq[(Double, Double)] =
 (r) => (thetaO to thetaF).map(theta => getCartesianCoordinates(r, theta))
 
 def getCartesianCoordinates(r: Double, theta: Double): (Double, Double) =
 ((r * Math.cos(theta)), (r * Math.sin(theta)))
 
 
 def draw(func: Double => Seq[(Double, Double)], scale: Double) 
 def getCartesianCoordinates(r: Double, theta: Double): (Double, Double) =
 ((r * Math.cos(theta)), (r * Math.sin(theta)))
 

• 15.
  15 First Class Functions defmain(args: Array[String]): Unit = {
 draw(getCurve(0, 90), 1)
 draw(getCurve, 2)
 }
 
 def getCurve: Double => Seq[(Double, Double)] =
 (r) => (0 to 360).map(theta => getCartesianCoordinates(r, theta))
 
 def getCurve(thetaO: Int, thetaF: Int): Double => Seq[(Double, Double)] =
 (r) => (thetaO to thetaF).map(theta => getCartesianCoordinates(r, theta))
 
 def getCartesianCoordinates(r: Double, theta: Double): (Double, Double) =
 ((r * Math.cos(theta)), (r * Math.sin(theta)))
 
 
 def draw(func: Double => Seq[(Double, Double)], scale: Double) def main(args: Array[String]): Unit = {
 draw(getCurve(0, 90), 1)
 draw(getCurve, 2)
 }
 
 
 def draw(func: Double => Seq[(Double, Double)], scale: Double)
• 16.
  16 First Class Functions defmain(args: Array[String]): Unit = {
 draw(getCurve(0, 90), 1)
 draw(getCurve, 2)
 }
 
 def getCurve: Double => Seq[(Double, Double)] =
 (r) => (0 to 360).map(theta => getCartesianCoordinates(r, theta))
 
 def getCurve(thetaO: Int, thetaF: Int): Double => Seq[(Double, Double)] =
 (r) => (thetaO to thetaF).map(theta => getCartesianCoordinates(r, theta))
 
 def getCartesianCoordinates(r: Double, theta: Double): (Double, Double) =
 ((r * Math.cos(theta)), (r * Math.sin(theta)))
 
 
 def draw(func: Double => Seq[(Double, Double)], scale: Double)
• 17.
  17 Type Strictness sealed traitPerson
 
 case class Student(name: String) extends Person
 
 case class Alumni(name: String) extends Person
 
 def getBusFare(person : Person): Int = {
 person match {
 case p: Student => 0
 case p: Alumni => 2
 }
 }
• 18.
  18 Options // Form askingfor person's gender
 // a) Female
 // b) Male
 // c) Don’t want to disclose
 
 def main(args: Array[String]): Unit = {
 val answers = Seq(Some("Female"), Some("Male"), Some(null), None)
 
 answers.map(a => a match {
 case Some(gender) =>
 if(gender == null){
 "the didn't want to disclose his or her gender"
 } else {
 s"The user's gender is $gender"
 }
 case None => "the user didn't pick a value on the form"
 })
 }
• 19.
  19 What’s next?
• 20.
  20 Keep Learning • Slides:http://www.slideshare.net/JorgePaez15/getting-functional-with-scala • Deploying a Scala server to Bluemix: https://www.ibm.com/innovation/milab/how- to-run-a-scala-web-app-on-ibm-bluemix/ • Free class: https://www.coursera.org/learn/progfun1
• 21.
  Thank You
 @jorgelpaez19 @IBM_MIL