Scala Type Hierarchy and Expressions

Type Hierarchy

Expressions
In imperative languages like Java/Python we execute instructions. For example IF conditional statement is an Instruction. Whereas in Scala, we execute expressions.

IF conditional statements are expressions that can return some value.

val aConditionValue = if (aCondition) 5 else 3
Code Blocks are also expressions that can return something
val someOtherValue = {
        if (someValue) 233 else 422
        42
    }

Code Blocks are commonly used expression blocks which can contain one or more expressions and the return type is the return value from the last expression.

val aCodeBlock = {
   if(true) 54
   56
}

Throwing exception from a method returns Nothing “()”
Any methods (println) that have side effects returns Unit
so on..

In functional programming languages writing loops are not encouraged. Whenever there is a need to write a loop we should go for recursion. Optimized way to write recursion is to use TAIL RECURSION technique.
To ensure we are using tail recursion we can use “@tailrec” before the function definition