In computer science, functional programming is a programming paradigm—a style of building the structure and elements of computer programs—that treats computation as the evaluation of mathematical functions and avoids changing-state and mutable data.

1. Harmeet Singh (Taara)
Sr. Software Consultant
http://harmeetsingh.in/

2. Agenda
✔
Functional Programming
✔
Functional Programming
✔
Functional Programming

3. Back2Basics
Albert Einstein had to
essentially go back to
school and learn a lot of
math so he could turn the
Theory of Special
Relativity into the Theory
of General Relativity.

4. Functional Programming
Runar Bjarnason

5. Functional Programming
What is Pure Function means???

6. Functional Programming
Pure Function is not
About first-class functions
Or higher-order procedures

7. Functional Programming
Functional Programming is not
about immutability

8. Functional Programming
Functional Programming is
Programming with pure functions

9. Functional Programming: Advantages
✔ Readability.
✔ Easy testing.
✔ Easy debugging.
✔ Meaningful signatures.
✔ Easy parallel-programming.
and more...

10. Functional Programming: Disadvantages
✔ Difficult to combine.
✔ Math terminology (monads, monoids etc).
✔ Recursion doesn't feel natural.
✔ Only immutable
✔ IO and others
and more...

11. Functional Programming: Algebra
// Algebra
f(x) = x + 1
f(x,y) = x + y
f(a,b,c,x) = a * x^2 + b*x + c
// Scala code
def f(x: Int) = x + 1
def f(x: Int, y: Int) = x + y
def f(a: Int, b: Int, c: Int, x: Int) =
a*x*x + b*x + c

12. Functional Programming: Algebra
val b = f(a)
val c = g(b)
Val d = h(c)
val result = x + y + z
PureFunctions+ ImmutableValues== Algebra

13. Functional Programming: HOF
Class SomeType {
def map(f: A => B): SomeType[B] { … }
def flatMap(f: A => SomeType[B]): SomeType[B] { … }
}

14. Functional Programming

15. Functional Programming
DEMO

16. Functional Programming: For Expression
Monadic Operator ( ← )

17. Functional Programming: For Expression

18. References:
✔ https://www.infoq.com/presentations/io-functional-side-effects
✔ https://alvinalexander.com/scala/examples-shows-differences-between-strict
✔ https://stackoverflow.com/questions/19617378/withfilter-instead-of-filter
✔ https://alvinalexander.com/scala/fp-book/how-enable-filtering-class-in-for-exp
✔ http://docs.scala-lang.org/tutorials/FAQ/yield.html
✔ https://alvinalexander.com/downloads/learning-fp-in-scala-0.1.1.pdf