![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)](https://image.slidesharecdn.com/uftalk-160927182752/85/Getting-Functional-with-Scala-11-320.jpg)
![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)](https://image.slidesharecdn.com/uftalk-160927182752/85/Getting-Functional-with-Scala-12-320.jpg)
![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))](https://image.slidesharecdn.com/uftalk-160927182752/85/Getting-Functional-with-Scala-13-320.jpg)
![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)))](https://image.slidesharecdn.com/uftalk-160927182752/85/Getting-Functional-with-Scala-14-320.jpg)
![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)](https://image.slidesharecdn.com/uftalk-160927182752/85/Getting-Functional-with-Scala-15-320.jpg)
![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)](https://image.slidesharecdn.com/uftalk-160927182752/85/Getting-Functional-with-Scala-16-320.jpg)
![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"
})
}](https://image.slidesharecdn.com/uftalk-160927182752/85/Getting-Functional-with-Scala-18-320.jpg)
Getting Functional with Scala
- 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" }) }
- 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