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# Scala

* Values cannot be re-assigned
* The type of a value can be omitted and [inferred](https://docs.scala-lang.org/tour/type-inference.html), or it can be explicitly stated:
  * `val x: Int = 1 + 1` 
* Variables are like values, except you can re-assign them. You can define a variable with the `var` keyword.

### Methods

Methods are defined with the `def` keyword.

```scala
def add(x: Int, y: Int): Int = x + y
println(add(1, 2)) // 3
```

A method can take multiple parameter lists:

```scala
def addThenMultiply(x: Int, y: Int)(multiplier: Int): Int = (x + y) * multiplier
println(addThenMultiply(1, 2)(3)) // 9
```

The last expression in the body is the method’s return value. (Scala does have a `return` keyword, but it is rarely used.

```scala
def getSquareString(input: Double): String = {
  val square = input * input
  square.toString
}
println(getSquareString(2.5)) // 6.25
```

### Classes

```scala
class Greeter(prefix: String, suffix: String) {
  def greet(name: String): Unit =
    println(prefix + name + suffix)
}
```

The return type of the method `greet` is `Unit`, which signifies that there is nothing meaningful to return. It is used similarly to `void` in Java and C.