Recursion and Repetition 9 23 2011 Opening Discussion Minute essay comments How close is Scala to Java Math on tests relative to homework Making negatives of variables b should work Space between and Motivation We 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 Recursion The 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 Recursion Now 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 Redirection One way to process data from a file is to write a script and use redirection scala script scala input txt This 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 Averaging Numbers I have some large files of numbers in the inclass code directory I want to use recursion and redirection to find the average of these If time allows let s think of some other things we might want to do with them Minute Essay What questions do you have about this topic We will do IcP 3 on Monday
View Full Document
Unlocking...