Pattern matching vs if-else

Question

I'm novice in Scala. Recently I was writing a hobby app and caught myself trying to use pattern matching instead of if-else in many cases.

user.password == enteredPassword match {   case true => println("User is authenticated")   case false => println("Entered password is invalid") } 

instead of

if(user.password == enteredPassword)   println("User is authenticated") else   println("Entered password is invalid") 

Are these approaches equal? Is one of them more preferrable than another for some reason?

Answer 1

class MatchVsIf {   def i(b: Boolean) = if (b) 5 else 4   def m(b: Boolean) = b match { case true => 5; case false => 4 } } 

I'm not sure why you'd want to use the longer and clunkier second version.

scala> :javap -cp MatchVsIf Compiled from "<console>" public class MatchVsIf extends java.lang.Object implements scala.ScalaObject{ public int i(boolean);   Code:    0:   iload_1    1:   ifeq    8    4:   iconst_5    5:   goto    9    8:   iconst_4    9:   ireturn  public int m(boolean);   Code:    0:   iload_1    1:   istore_2    2:   iload_2    3:   iconst_1    4:   if_icmpne   11    7:   iconst_5    8:   goto    17    11:  iload_2    12:  iconst_0    13:  if_icmpne   18    16:  iconst_4    17:  ireturn    18:  new #14; //class scala/MatchError    21:  dup    22:  iload_2    23:  invokestatic    #20; //Method scala/runtime/BoxesRunTime.boxToBoolean:(Z)Ljava/lang/Boolean;    26:  invokespecial   #24; //Method scala/MatchError."<init>":(Ljava/lang/Object;)V    29:  athrow 

And that's a lot more bytecode for the match also. It's fairly efficient even so (there's no boxing unless the match throws an error, which can't happen here), but for compactness and performance one should favor if/else. If the clarity of your code is greatly improved by using match, however, go ahead (except in those rare cases where you know performance is critical, and then you might want to compare the difference).