Lab 4: Selection sort

You may find it interesting to compare the versions of tddFuncs.h and tddFuncs.cpp from lab 2 with the ones from this lab.

You do NOT need to make any changes to these files. However, they serve the purpose of showing how we can use template functions in C++ and Template Specialization to create code that is more "DRY", i.e. follows the adage "Don't Repeat Yourself".

Here are links to the versions of these files from lab 2 and this week:

Some things to notice:

• In the lab2 version of tddFuncs.cpp, there was duplicated code–identical versions of assertEquals for both int and std::string. In the lab4 version, this has been DRY'ed up and factored out into a template in the lab4 tddFuncs.h.
• In the lab4 version of tddFuncs.cpp, there are also two overloaded versions of the function assertEquals that are NOT using the template. These versions of the function are needed because C-strings (i.e. const char * and const char * const values) cannot be compared with the == operator. The version for two C-strings used strcmp instead, while the version for a C-string and an std::string simply converts the C-string to a C++ string and invokes the template version for std::string.

Again, you don't need to do anything with this for this lab, so if you want to gloss over this for now and come back to it later, that's fine. You need to look it over though, and understand what is going on.

A final note: the way we overloaded the functions here does work, and it has the advantage of being easy to understand and follow. However, it is probably not the "current best practice" way of handing this, and strictly speaking, is not "template specialization", it is rather just "garden variety overloading". We'll go over the "better way", i.e. true template specialization, in a future lab or lecture (although each variant has its uses). For now, if you are curious, and want to "read ahead", consider the following StackOverflow link:

http://stackoverflow.com/questions/17344405/template-function-specialization-vs-overloading

In this week's Makefile, as with last weeks, we have the following.

CXXFLAGS = -Wall -Wextra -Wno-unused-parameter -Wno-unused-private-field

# Change to this before final submission:
# CXXFLAGS = -Wall -Wextra -Werror

See the explanation in lab 2 of these two definitons for CXXFLAGS. It will be important for you to modify these before submitting to make sure that your code will compile with those flags set.

The Student.h and Student.cpp classes are mostly unchanged from lab 2, except for the addition of a few new methods.

Please look those over–these are mostly methods for reading in a Student from a comma-separated string, and are there so that we can read in students from a CSV file (i.e. a file of comma separated values) into a Roster.

The Roster.h and Roster.cpp files, though, are new.

You'll see that the Roster.h file contains the specification of a class that represents a collection of Students. It represents this collection with a simple fixed size C++ array of pointers to Student objects. THERE ARE CERTAINLY BETTER WAYS TO IMPLEMENT A COLLECTION OF STUDENTS. The point for this week's lab, though, is to understand sorting algorithms.

We will implement a selection sort on the array of pointers to Student objects. Since we only have to swap the pointers in the array–we don't have to swap the entire Student object–our algorithm will run in the same amount of time no matter how large the actual Student objects may be. In general, this is a good idea if/when one is working with large objects.

The files where you will be making changes this week are:

• Student.cpp, where you'll be updating the methods that you wrote in lab 2. Don't just copy over the entire file though, because if you do, you'll lose the new methods that we supplied you with in the starting point code.
• Roster.cpp, where you'll be replacing stubs with correct code.

What you should do next is to look through the test cases in testStudent.cpp (which includes all the tests from the three test files in lab 2) and testRoster1.cpp, testRoster2.cpp and testRoster3.cpp

Look over these files and understand how they work. Then, type make tests to compile and run all of the tests.

You can also type, for example, make testRoster1 and ./testRoster1 to make and run these tests one at a time.