Scala Control Structure

Scala has a handful of built-in control structures, only if, while, for, match, try, and function calls.

Almost all Scala control structures produce a value (while and do while not producing meaningful values, but also return a value of unit type, called unit value, written as ()). Unit value () is where Scala's unit differs from Java's void. Typically, an assignment statement returns the unit value (). So the code that is often used for file reads in Java code:

var line = ""

while (line = Fr.readline ()) = "") {

println ("Read:" + Line)}

Even if it's a Scala style, it doesn't work because line = Fr.readline () is returned as an assignment statement (), and the string "" is not always equal, so it is trapped in a dead loop.

Scala Control Structure