Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Recursion and Repetition2-9-2011Opening DiscussionMinute essay comments:Copy and paste commands in vi.Let's look at solutions to the interclass problem.Finishing the intersecting squares.The match ExpressionThere is a second conditional expression in Scala called match.expr match {case pattern => exprcase pattern => expr...}There are lots of options for the pattern, but the simplest one is literal values.Lowercase names will be bound as val declarations.MotivationWe have the ability to do things once and to control whether or not certain things happen that once.Computers are really great for doing things multiple times.Reading a whole file or doing something until the user tells us to stop.Mathematical RecursionThe idea of recursion comes from mathematics.A function is recursive if it is defined in terms of itself.All recursive functions will have at least two cases.One where the function refers to itself.A base case where it doesn't refer to itself.Let's look at some examples of this.Programmatic RecursionNow I want us to write some Scala functions that are recursive.They will look much like the math functions.We have to provide a return type.One argument changes to tell us when to stop.Scripts and RedirectionOne way to process data from a file is to write a script and use redirection.scala script.scala < input.txtThis way you don't have to enter the input over and over. Also handy if the input is really large.We'll learn other ways to deal with files later.Minute EssayMake sure you are reading.What questions do you have about this topic?Minute EssayMake sure you are reading.What questions do you have about this
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