Dictionary

Type parameters- Types in scala can be parametrized. That means you can add additional information that goes with main type.

List[Double](1,2,3) //List(1.0, 2.0, 3.0) (result)

List[String]("A","B","C") //List(A, B, C) (result)

This information is not available at runtime. Instead are types are replaced with "Any" type

Pure function - does not have any side effects.
- rest of code can affect processing only by giving input - functions can affect rest of code only by result

Traversable- Base type for all Scala collections
- contains foreach method
- might be strict (List) or non-strict (Stream)
- might be ordered (Seq) or non-ordered (Set)

strict collection- all elements are computed when collection is computed.

non-strict collection- (lazy collection) - computation of elements may be deferred.

persistent collection
- immutable
- operations on collection return new updated structure
- updated structure reffers to original and contains only differences
- memory efficient

val items1 = List(1,2,3)
val items2 = items1.updated(1, "A")

- there's no way to modify original collection (items1)
- though update method returns new collection (items2)
- new collection contain only changes and reference to original
- old items are shared by both collections

immutable- once created object does not change

REPL- (Run-Eval-Print Loop) - shell for Scala.
Simple programming enviroment where user enters expressions, next they are evaluated, results are printed and process is repeated.

scala
Welcome to Scala version 2.10.3 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_25).
Type in expressions to have them evaluated.
Type :help for more information.

scala> println("Hello world")
Hello world

scala> exit