Is this an abuse of Scala pattern matching?

Question

As in most languages, Scala has an if statement. However, using pattern matching I can achieve the exact (?) same result using code of the form:

(condition) match {
  case true =>  { /* handle the true case */ }
  case false => { /* handle the false case */ }
}

This feels like an abuse of the mechanism, but I find it hard to explain why. Can wiser heads help me understand the position?

Seems to be similar q to https://stackoverflow.com/questions/7986641/pattern-matching-with-guards-vs-if-else-construct-in-f to which the answer is 'it depends' but pattern matching preferred. — Andy, Dec 08 '17 at 11:53
Match as switch: http://alvinalexander.com/scala/using-match-expression-like-switch-statement — cchantep, Dec 08 '17 at 12:36

score 4 · Accepted Answer · answered Dec 08 '17 at 12:22

I wouldn't normally use it, although yes, it's a matter of taste. But there are cases where I might resort to this construction. For example when I need to send as argument a higher order function that reveives a Boolean value (using Scala's PartialFunction syntax):

future.onSuccess {
  case true => ???
  case false => ???
}

Or when there are extra conditions, something along these lines:

value match {
  case true if condition1 => ???
  case true if condition2 => ???
  case true if condition3 => ???
  case false => ???
}

score 4 · Answer 2 · answered Dec 08 '17 at 12:47

The match compiles to the equivalent of

val scrutinee = condition
if (scrutinee == true) /* handle success case  */
else if (scrutinee == false) /* handle failure case */
else throw new MatchException()

so it's semantically identical. But why would you? It's more verbose, more syntax-heavy, and less clear than the if expression.

Is this an abuse of Scala pattern matching?

2 Answers2