hautrian:scala 2001> scala
Welcome to Scala 2.11.12 (OpenJDK 64-Bit Server VM, Java 1.8.0_252).
Type in expressions for evaluation. Or try :help.

scala> 3+4
res0: Int = 7

scala> res0
res1: Int = 7

scala> val x = 5
x: Int = 5

scala> x + 4
res2: Int = 9

scala> x = 4
<console>:12: error: reassignment to val
       x = 4
         ^

scala> var y = "Hello"
y: String = Hello

scala> y = y + " World!"
y: String = Hello World!

scala> y
res3: String = Hello World!

scala> def inc(x) = x+1
<console>:1: error: ':' expected but ')' found.
def inc(x) = x+1
         ^

scala> def inc(x:Int) = x+1
inc: (x: Int)Int

scala> inc(5)*2
res4: Int = 12

scala> class ListInt(elem: Int, next: ListInt)
defined class ListInt

scala> val xs = new ListInt(1, new ListInt(2, null))
xs: ListInt = ListInt@724bf25f

scala> class List[T](elem: T, next: List[T])
defined class List

scala> val xs = new List(1, new List(2, null))
xs: List[Int] = List@4b87760e

scala> class List[T](elem: T, next: List[T]) {
     |   def printList():Unit = {
     |     println(elem)
     |     if (next != null) next.printList()
     |   }
     | }
defined class List

scala> val xs = new List(1, new List(2, null))
xs: List[Int] = List@269222ae

scala> xs.printList()
1
2

scala> xs.printList
1
2

scala> xs printList
warning: there was one feature warning; re-run with -feature for details
1
2

scala> 1+2
res8: Int = 3

scala> (1).+(2)
res9: Int = 3

scala> val inc = (x:Int) => x+1
inc: Int => Int = <function1>

scala> inc(3)
res10: Int = 4

scala> val num14 = List(1,2,3,4)
num14: List[Int] = List(1, 2, 3, 4)

scala> num14.filter((x:Int) => x > 2)
res11: List[Int] = List(3, 4)

scala> num14.filter((x) => x > 2)
res12: List[Int] = List(3, 4)

scala> num14.filter(x => x > 2)
res13: List[Int] = List(3, 4)

scala> num14.filter(_ > 2)
res14: List[Int] = List(3, 4)

scala> def add(a: Int, b: Int) = a + b
add: (a: Int, b: Int)Int

scala> def inc = add(1,_)
<console>:12: error: missing parameter type for expanded function ((x$1) => add(1, x$1))
       def inc = add(1,_)
                       ^

scala> def inc = add(1,_:Int)
inc: Int => Int

scala> inc(6)
res15: Int = 7

scala> def twice(f: Int => Int, x: Int) = f(f(x))
twice: (f: Int => Int, x: Int)Int

scala> twice(inc,42)
res16: Int = 44

scala> def twice[A](f: A => A, x: A) = f(f(x))
twice: [A](f: A => A, x: A)A

scala> twice(inc,42)
res17: Int = 44

scala> twice((x: Boolean) => !x, true)
res18: Boolean = true

scala> def byValue(x: Int, y: Int) = if (x==0) y else x
byValue: (x: Int, y: Int)Int

scala> byValue(42, 99)
res19: Int = 42

scala> byValue(42, 1/0)
java.lang.ArithmeticException: / by zero
  ... 32 elided

scala> def byName(x: Int, y: =>Int) = if (x==0) y else x
byName: (x: Int, y: => Int)Int

scala> byName(42, 1/0)
res21: Int = 42

scala> def m(y: Int) =
     |  y match {
     |    case 0 => "null"
     |    case 42 => "meaning of life"
     |    case _  => "something else"
     |  }
m: (y: Int)String

scala> m(0)
res22: String = null

scala> m(41)
res23: String = something else

scala> m(42)
res24: String = meaning of life

scala> def generalSize(x: Any) = x match {
     |   case s: String => s.length
     |   case m: Map[_,_] => m.size
     |   case _           => -1
     | }
generalSize: (x: Any)Int

scala> generalSize("sgssgsg")
res25: Int = 7

scala>