`Case is 'an instance of a particular situation; an example of something occurring'.
So my question is - why Scala 'case' classes are named as 'case'? What is the point? Why it is 'case', not 'data' class or something else? What does mean 'case' in that.. case :)
The primary use of the case keyword in other languages is in switch-statements which are mostly used on enums or comparable values such as ints or strings being used to represent different well-defined cases:
switch (value)
{
case 1: // do x -
case 2: // do y -
default: // optional
}
In Scala these classes often represent the specific well-defined possible instances of an abstract class and are used in much the same way imperative code uses switch-statements within match-clauses:
value match {
case Expr(lhs, rhs) => // do x
case Atomic(a) => // do y
case _ => // optional, but will throw exception if something cannot be matched whereas switch won't
}
Much of the behavior of case classes such as the way they can be constructed aims at facilitating/enabling their use in such statements.