Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Functions9-13-2010Opening DiscussionLet's look at solutions to the interclass problem.Minute Essays:Why isn't there a decent API available?How many different commands will you have to memorize as a CS major?I/O redirection.ACM and Major's e-mail list.Functions in MathLet's review the concept of functions from math.In algebra a function would take one or more values and give you back a value. The values were generally numbers.In higher level math this is generalized with things like sets.In math functions the same input leads to the same result.Functions in ProgrammingThe concept of a function is critically important to programming.Functions can take one or more arguments and give us back values. (Most languages allow only one return value.)Let's think of some examples of functions that we could write.Functions in ScalaWe declare functions in Scala using def. Here is the general form.def name(ar g1:Type1, arg2:Type2, ...):Type = expressionThe argument list can have zero or more elements. If there are zero even the parentheses can be left off.Function arguments must have types.The return type is optional, but it is recommended.Why Functions?Functions are used in programs for a number of reasons.Reduce code duplication. You can call the same function multiple times and only write it once.Improve readability and maintainability. Good function names make it easier to read. Small functions are easier to test and debug.Break problems down/problem decomposition.Problem DecompositionNever solve a hard problem. If a problem is hard, break it into smaller problems that are easier. Repeat until you are only solving trivial problems.Top-downThis is the “normal” approach where you start with the full problem and break it into pieces.Bottom-upSometimes you realize that different trivial pieces will be useful and build up from those.Minute EssayDo you have any questions about functions?Interclass Problem:Write two functions that do unit
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