What is Scala?

• Scala fuses OOP and FP
  : scala is scalable
  • object oriented
    • every val is an obj
    • every operation is a method call
  • scala is functional
    • funcs are first-class values
    • operations of a program should map input values to output values rather than change data in place

Immutable variables and value types

val (immutable) :

• can't be reassigned

• double, int, bool, string is the most important

val (mutable) :

• can be reassigned
• pros and cons
  • pros:
    • data won't be changed inadvertently
    • code is easier to reason about
    • have to write fewer tests
  • cons
    • extra memory required due to dat copying

Scripts, applications and real-world workflows

scala scripts

• a sequence of instructions in a file, executed sequentially
• useful for smaller projects
• at a command prompt, the scala command executes a script by wrapping it in a template and then compiling and executing the resulting program

Interpreted language vs. compiled language

Scala applications

• compiled explicitly then run explicitly
• consist of many source files that can be compiled individually
• useful for longer programs
• no lag time since applications are precompiled

Array

Collections

• mutable
  • can be updated/extended in place
• immutable

and Array is mutable.

• Initialize elements of the Array

강사님 ㅋㅋㅋㅋㅋ Bye Alex 무엇 ㅋㅋㅋㅋㅋㅋ

• Recommendation : use val with Array in Scala

• mix and match the parameters in Array

Lists

• Array is mutable and Lists is immutable obj

How Lists are useful while immutable

• list has methods, like all of Scala collections

var players = List("A", "B")
players = "C" :: players

<Returns>
palyers: List[String] = List(C, A, B)

• :: called 'Cons'

Scala's static type system

Scala is Compiled, statically-typed languages.

• Relational and logical operators
  • Relational

    • , < , >= , <= , == , !=

  • Logical
    • && , || , ! (not)

• foreach