Return values

As with most functional languages, most control structures ( if, for, try ) return values. The common java idiom:

1. String name=null;
2. if( xxx ) name="yyy";
3. else name="zzz";

can be replaced by

1. val name = if( xxx ) "yyy"; else "zzz";

The benefit (other than less boiler plate code) is that name can now be a val instead of a var.

Another other point about returns: The return keyword is not required when returning a value from methods or control structures. The last value is always the return value. This is why you will get an error if the last line in a method or control structure is an assignment.

Examples:

1. scala> val name = if( 1==2 ) "Jesse" else "Mauricio"
2. name: java.lang.String = Mauricio
4. scala> println(name)
5. Mauricio
7. scala> val collection = for( i <- 1 to 100; if(i%20 == 3) ) yield i
8. collection: Seq.Projection[Int] = RangeFM(3, 23, 43, 63, 83)
10. scala> collection.foreach( i => print( i +" ") )
11. 3 23 43 63 83
13. scala> val someObj:AnyRef = "Hello"
14. someObj: AnyRef = Hello
16. scala> val choice = someObj match {
17.      | case _:java.io.File => "File"
18.      | case _:String => "String"
19.      | case _ => "Dunno"
20.      | }
21. choice: java.lang.String = String
23. scala> val result = try {
24.      | "two".toInt
25.      | }catch{
26.      | case e:NumberFormatException => -1
27.      | case _ => 0
28.      | }
29. result: Int = -1
30. scala> var i=0
31. i: Int = 0
33. // while and do-while do not have return values
34. scala> while( i<4 ){
35.      | "22"
36.      | i += 2
37.      | }
39. scala> println( if(i>0) "great" else "less" )
40. great
42. // code blocks return the last statement
43. scala> val m = {
44.      | val x = 1
45.      | x + 2
46.      | }
47. m: Int = 3