[Lecture Notes]Programming Languages: Scala,Columbia University

1. def simplifyTop ( expr : Expr ): Expr = expr match {
   
2. case UnOp ( " -" , UnOp ( " -" , e )) = > e // Double negation
   
3. case BinOp ( " + " , e , Number (0)) = > e // Adding zero
   
4. case BinOp ( " * " , e , Number (1)) = > e // Multiplying by one
   
5. case _ = > expr
   
6. }
   
7. scala > simplifyTop ( UnOp ( " -" , UnOp ( " -" , Var ( " x " ))))
   
8. res0 : Expr = Var ( x )

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1. Using tuples in pattern matching:
   
2. def tupleDemo ( expr : Any ) =
   
3. expr match {
   
4. case (a , b , c ) = > println ( " matched " + a + b + c )
   
5. case _ = > // returns Unit
   
6. }
   
7. scala > tupleDemo (( " a " , 3 , " - tuple " ))
   
8. matched a 3 - tuple

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