> For the complete documentation index, see [llms.txt](https://openai.gitbook.io/code-cheatsheets/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://openai.gitbook.io/code-cheatsheets/all/scala.md).

# README

Semicolon optional unless multiple statements on same line

## Main

```scala
object session extends App {
    println("Hello world")
}

object session {
    def main {
        println("Hello world")
    }
}
```

## Basic Defining Blocks

* Call by value: evaluates the function arguments before calling the function
* Call by name: evaluates the function first, and then evaluates the arguments if need be

```scala
def example = 2      // evaluated when called
val example = 2      // evaluated immediately and immutable
var exmaple = 2 //variable and immediate
lazy val example = 2 // evaluated once when needed

def loop = loop //won't loop forever at this line
val loop = loop //will loop forever at this line

def square(x: Double)    // call by value
def square(x: => Double) // call by name
def myFct(bindings: Int*) = { ... } // bindings is a sequence of int, containing a varying # of arguments
```

## Expressions

the building block of scala

Blocks {} are an expression that returns the last expression's value. so can be stored in variables returned by functions and be parameters

```scala
var y = 2        //variable    
val x = 1        //immutable
```

## Basic Types

"" - strings

'' - chars

Any is base type of all types and defines:

* \== - calls Java `equals`
* hashCode 
* toString

`AnyRef` is basetype of all reference types and `AnyVal` is base type of all primitative types

`Nothing` is subtype of every type(so it can be passed/returned), yet no value has type nothing. Used when fts fail to return anything by ending abnormally(errs) or element type of empty collections(Set\[Nothing]).

The type of `null` is Null i.e `val x = null`. `null` is subtype of `AnyVal`

Useful b/c can write ft like `if x 1 else false` which will be type `ddddddAnyVal`