Scala - complex conditional pattern matching

Question

I have a statement I want to express, that in C pseudo-code would look like this:

switch(foo):
    case(1)
        if(x > y) {
            if (z == true) {
                doSomething()
            }
            else {
                doSomethingElse()
            }
        }
        return doSomethingElseEntirely()
        
    case(2)
        // essentially more of the same

Is a nice way possible with the scala pattern matching syntax?

Tomas Petricek · Accepted Answer · 2011-07-24 00:50:47Z

49

If you want to handle multiple conditions in a single match statement, you can also use guards that allow you to specify additional conditions for a case:

foo match {    
  case 1 if x > y && z => doSomething()
  case 1 if x > y => doSomethingElse()
  case 1 => doSomethingElseEntirely()
  case 2 => ... 
}

answered Jul 24, 2011 at 0:50

Tomas Petricek

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6 Comments

Rex Kerr Over a year ago

This doesn't actually match what the OP wrote. The control flow is different; on x>y&&z, the OP executes doSomething(), return doSomethingElseEntirely(), while yours returns doSomething() alone.

Tomas Petricek Over a year ago

@Rex - Good point, thanks. I didn't quite get it because OP's code is missing some opening and closing curly braces. Anyway, it should be easy to fix the body accordingly.

The Archetypal Paul Over a year ago

To me, this doesn't make it clear the x > y test is common to the first two branches. There's nothing inherently wrong with if/then/else and in this case, it's clearer (IMO).

Vincenzo Maggio Over a year ago

@Paul I agree, but it was the OP to ask for this kind of solution! :)

Valentin Tihomirov Over a year ago

I fail to use guards in the exception handling

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