Scala Expressions and Functions

As opposed to instructions, everything in Scala is considered an expression. Even if/else statements themselves in Scala are expressions.

For Loops

For loops are not recommended in Scala. They return Unit which in itself is equivalent tonull. This is the case for side effects - an intergral part of understanding Scala.

Code Blocks

Note that if you write a code block, the last value in the code block is returned as the value.

val codeBlock = {
    val a = 1
    val b = 2

    if(a < b) "hi" else "bye"
}

println(codeBlock)
// evaluates to "hi"
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Examples of Expressions and Side Effects

"hello" // type String
println("hello") // type Unit

// type Boolean
val a = {
    2 < 3
}

// type Int value 10
val b = {
    if(a) 123 else 321
    10
}

// c is of type Unit
var i = 0
val c = while (i < 10) {
    i += 1
}
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Functions

object Functions extends App {
    // this works because we know everything is an expression
    def functionExample(a: String, b: Int): String = a + " " + b

    def parameterlessFunc(): Int = 42
    println(parameterlessFunc())
    // also valid in Scala to call func
    println(parameterlessFunc)

    def repeterFunc(a: String, n: Int): String  = {
        if (n == 1) a
        else a + repeterFunc(a, n-1)
    }
}
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