Chapter 7: High Quality Routines By Raj Ramsaroop

 A routine is a:  Function (C++).  Method (Java).  Procedure (Visual Basic).  Macro.  A routine should have a single purpose. What Is A Good Routine?

Example: A Bad Routine

 Name: HandleStuff().  Too many parameters.  No logical ordering to parameters.  Looks like it’s trying to do more than one task.  Not logically laid out.  Input variable is changed.  Unused parameters. Why Was That A Bad Routine?

 Biggest reason: reduce complexity.  Minimize code, avoid duplicate code.  Make your code more maintainable.  Easier to read. Why/When Create A Routine?

 Avoid duplicate code.  Only need to check one place.  Avoid writing the same thing twice.  Similar code in different routines – split them up.  Hide sequences.  Keeps code simple.  E.g. if you get data from a user and data from a file, neither routine should depend on each other. Why/When Create A Routine? Cont.

 Improve portability.  Make your code independent of hardware/software, or the project you are working on.  Can be reused – enforces object-oriented concepts.  Simplify complicated boolean tests.  E.g. isVisible()  Details of the test are out of the way.  The name is descriptive.  Emphasizes it’s significance. Why/When Create A Routine? Cont.

 Depends:  If you keep repeating the same line.  One line of code can balloon into something bigger.  Makes code more readable. Can Code Sometimes Be Too Small For A Routine?

 Cohesion refers to how closely the operations in the routine are related.  Ensures routines perform one task well – and nothing else.  Acceptable types of cohesion:  Functional cohesion – the best type, is when a routine performs only one function.  Sequential cohesion.  Communicational cohesion.  Temporal cohesion. Routine Cohesion

 Procedural cohesion – operations that are in a specific order and are combined for that specific reason.  Logical cohesion – basically methods with big ‘if statements’  Operations are not usually logically related.  Only time this would be acceptable would be something like an event handler.  Coincidental cohesion – if you have this it probably means you need to redesign your program! Unacceptable Types Of Cohesion

 Name can be as long as it needs to be – as long as it doesn’t sound silly!  Make it descriptive.  Avoiding meaningless verbs (e.g. processOutput(), calculateData()).  Don’t differentiate functions solely by a number!  Use what the function returns to name the function. E.g. customerId.next(), printer.isReady()  To name a procedure, use a strong verb followed by an object. E.g. printReport(), calculateInvoice()  Use opposites such as get/set, open/close, first/last etc Naming Routines

 A line is a noncomment, nonblank line of code.  Book suggests up to 200 lines.  They can be as long as they need to be as long as you focus on cohesion. How Long Should A Routine Be?

 Put parameters in “input-modify-output” order.  As opposed to randomly or alphabetically.  Implies a sequence of operations.  If several routines take similar parameters, put them in the same order.  Use all parameters.  Status and error variables go last.  Don’t use routine parameters as working variables.  Document the input variables (range, units, values that should never appear etc).  Limit number of parameters to 7.  Check parameter types (mismatched types etc). Using Routine Parameters

 A function is a routine that returns something.  A procedure is a routine that does something, but does not return anything.  You can combine the two.  Return values should return an object, not a reference or pointer to local data. When To Use A Function Or Procedure And Return Values