An overview of modern programming languages, with Kotlin as an example. We examine features of these languages including Groovy, Swift, and Go to point the trend in these languages.

1. Modern Programming
Languages - Overview
Ayman Mahfouz
July 2018
With Kotlin as an Example

2. Biography
- VP of Engineering at Webalo (webalo.com)
- Los Angeles based
- Branch in Alexandria
- UX4IIoT
- 20+ years of software development
- PhD. in software engineering
- BSc. Computer Science - Alexandria 1997

3. Programming Languages
Pascal C C++
Java
Python C# Objective-C ActionScript
Scala Ruby Octave
JavaScript
Go TypeScript Kotlin
BASIC
Swift Groovy

4. Why Many Languages Exist?
Optimized for different objectives
● Productivity
● Readability
● Portability
● Performance
○ Compile-time
○ Runtime

5. Some Notable Languages
Released By Notes
Groovy 2007 Pivotal Concise, easy-to learn, Java-interoperable, scripting
language for the JVM.
Go 2009 Google High-speed compilation compared to C , built-in
support for concurrency.
Swift 2014 Apple Many safety and syntax improvements to replace
Objective-C.
Kotlin 2016 JetBrains Designed to be “better than Java” - Interoperable for
incremental migration.

6. Kotlin Arrives!
● Paid little attention until Google I/O announcement.
● Android Studio Canary 3.
● Immediately fell in love
○ Strong Typing
○ Brevity
○ Expressiveness
○ Interoperability
○ Growing support
● Starts from where others ended (Java, Python, Go, Swift)
● One app built on github.
● Still learning.

7. Brevity
Null Safety
Conditionals
Smart Cast
Lambdas
Collections
Features we will go through:

8. Brevity
In Java, one would normally write this:
With my background, I translated this into Kotlin verbatim:
Not idiomatic but still
shorter! Can you spot
the omissions?
● No ;
● No “new”
● “override” is a modifier
● “:” not “implements”
● “public” is default
● Return type
In Java one would typically write code like this:

9. Brevity
Using “Single Expression Function” syntax
Pass a lambda expression to a function that accepts a single-method interface

10. Brevity
Omit parameter type
Omit parameter name as well
Eliminate left hand side completely
Lambda expression only argument so we can eliminate the parenthesis
Omit parameter type

11. Brevity - From Java to Kotlin
to Kotlin ...
From Java ...

12. We will go through:
Brevity
Null Safety
Conditionals
Smart Cast
Lambdas
Collections

13. Null Safety - Explicit handling
The dreaded NPE
Handle explicitly

14. Null Safety - Java Optionals
Handle via Java 8 Optionals - very verbose!
Handle by convention:
- Special member naming (IfAny)
- Null checks in constructor
- Hand-coded
- Annotations
- Aspects
Or let it throw! (pun intended)

15. Null Safety - Safe Navigation
Kotlin safe navigation operator
Compile-time language-enforced null safety
Forced init
Force null guard
Allowing late init
Conscious NPE

16. We will go through:
Brevity
Null Safety
Conditionals
Smart Cast
Lambdas
Collections

17. Conditionals
I cringe when I see if statements that look like this
Use the ternary operator please!

18. Conditionals - Expressions
In Kotlin, if statement is an expression
Combined with single expression function shorthand
So you can write a function like this

19. Conditionals - when
I hate “Switch” statements!
But I love “when” expressions!
1. No annoying “break” or even “case”
2. Match against any type
3. Switch variable can be of any type
4. The “else” section is mandatory

20. We will go through:
Brevity
Null Safety
Conditionals
Smart Cast
Lambdas
Collections

21. Smart Cast
In Java explicit cast is needed
In Kotlin Smart Cast takes place automatically

22. Smart Cast
In Java

23. Smart Cast
In Kotlin

24. Smart Cast - Nullables
Automatic cast to non-null

25. We will go through:
Brevity
Null Safety
Conditionals
Smart Cast
Lambdas
Collections

26. Lambdas
Think of it as a “function literal”
The function “Array” produces an array by applying a lambda

27. Lambdas - Higher-order Functions
Higher-order functions: functions that take other functions as arguments

28. Lambdas - Closures
Closures: lambdas can access variables in their outer scope

29. We will go through:
Brevity
Null Safety
Conditionals
Smart Cast
Lambdas
Collections

30. Collections
With Lambdas
it

31. Collections - Streaming
Chaining lambda operations

32. Collections - Immutability
In Java both mutable and immutable collections implement the same interface
Kotlin uses different interfaces - Compile error

33. What about the others?

34. ● Brevity
○ No semicolons
○ Optional “return”
○ Variable types
○ Omit parens in a call
○ Default imports
● Null Safety
● Closures
● Most of other Kotlin features
● And more
○ Parameterized Strings
Groovy
def list = [1, 2, 3]
list.each { println it }
person?.address.?city
def name = ‘World’
println “Hello $name!”

35. Swift
● Brevity
○ No semicolons
○ Implicit variable types
● Null Safety
● Closures
● Ranges
● Switch
○ Any type
○ Not just equality
○ No fallthrough
● Other
○ Parameterized Strings
○ Dynamic Extension
for i in 0..3 { println(“i”) }
extension Double {
c2f -> Double() {
return self * 9 / 5 + 32
}
}
…
let c = 100.0
print(c.c2f())

36. result, error := callSomeFunction()
Go
● Brevity
○ No semicolons
○ Implicit variable types
○ (But must use braces sometimes)
● Null Safety
● Switch
○ Non-constants
○ (But same type)
● Closures
● Multiple return values
● Missing some features
○ e.g. Inheritance
if i % 2 == 0 {
// even
} else {
// odd
}

37. Comparison Matrix
JVM GC Classes No ; Type
Inference
Safe
Null
If Expr Rich
Switch
Closure Variable
Arguments
Collection
Streaming
Dynamic
Extension
Tuples
Kotlin
✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
Groovy
✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
Swift
✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
Go
✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

38. Thank You!
Ayman Mahfouz
amahfouz@gmail.com
www.linkedin.com/in/amahfouz/
amahfouz.wordpress.com
github.com/amahfouz
amahfouz.com
AymanMahfouz.com