CS 3060: Programming Languages
The Scalable Language
Day 1
Key Points
- Oh so Java-like
- Runs on the Java virtual machine
- Uses Java libraries directly
- Statically typed (but doesn't always feel like it)
- Hybrid: Supports both object-oriented and functional programming paradigms
Key Points
- Type inference
- Functional concepts
- Immutable variables
- Advanced programming constructs
Running a File
The Code
object HelloWorld {
def main(args: Array[String]) {
println("Hello, world!")
}
}
Interactive Shell
HelloWorld.main(null)
Compile & Execute
scalac HelloWorld.scala
scala HelloWorld
Without a Main
object HelloWorld extends App {
println("Hello, world!")
}
Script
object HelloWorld extends App {
println("Hello, world!")
}
HelloWorld.main(args)
Script
println("Hello, world!")
Is Scala strongly typed?
"abc" + 4
4 + "abc"
4 + "1.0"
4 * "abc"
Output
println("My magic output...")
print("My magic output...")
Variables
val a = 1
val b = 3
val a:Int = 1
val b:Int = 3
Conditionals
val a = 1
val b = 3
if(b<a){
println("true")
}else{
false("true")
}
Loops
While Loops
def whileLoop {
var i = 1
while(i <= 3) {
println(i)
i += 1
}
}
whileLoop
For Loops
def forLoop {
println( "for loop using Java-style iteration" )
for(i <- 0 until args.length) {
println(args(i))
}
}
forLoop
For Loops
def forLoop {
println( "for loop using Java-style iteration" )
args.foreach { arg =>
println(arg)
}
}
forLoop
Ranges
The Basics
val range = 0 until 10
range.start
range.end
range.step
Increments
(0 to 10) by 5
(0 to 10) by 6
(0 until 10 by 5)
Direction
val range = (10 until 0) by -1
val range = (10 until 0)
val range = (0 to 10)
val range = 'a' to 'e'
Tuples
Basics
val person = ("Elvis", "Presley")
val (x, y) = (1, 2)
val (a, b) = (1, 2, 3)
Lists
Basics
val a = List(1, 2, 3)
a(2)
One catch
Nil
Sets
Basics
val animals = Set("lions", "tigers", "bears")
animals + "armadillos"
animals - "tigers"
animals + Set("armadillos", "raccoons")
animals ++ Set("armadillos", "raccoons")
animals -- Set("lions", "bears")
A little more...
animals ** Set("armadillos", "raccoons", "lions", "tigers")
Set(1, 2, 3) == Set(3, 2, 1)
Methods
def double(x:Int):Int = x * 2
def double(x:Int):Int = {
x * 2
}
Methods
def name(p1: Type1, p2: Type2) [:returnType] = {
if(original.length <= maxLength)
return original;
original.substring(0, maxLength - suffix.length) + suffix;
}
def ellipse(original: String, maxLength: Int) : String = {
if(original.length <= maxLength)
return original;
original.substring(0, maxLength - suffix.length) + suffix;
}
Left for you
- Random Number Generation
- Iteration
- String functions