This document provides an introduction to functional programming and the Scala programming language. It discusses core concepts of functional programming like immutable data, pure functions, expressions over instructions, and first-class functions. It provides examples comparing imperative Java code to equivalent functional Scala code. The document also outlines benefits of functional programming like simpler concurrency, optimizations, easier debugging, and cleaner code. It concludes by providing additional resources for learning Scala and functional programming.

1. Getting Functional with Scala
An Introduction to Functional Programming and the Scala Programming Language
September, 2016

2. 2
Software Engineer at IBM 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 yours start?
http://www-03.ibm.com/employment/entrylevel_campus.html

5. 5
What is Functional Programming?

6. 6
Function Not a Function

7. 7
Core Ideas
• Data is 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
def main(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
def main(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
def main(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
def main(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
def main(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 trait Person
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 asking for 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"
})
}

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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