In this lab you will practice sorting a vector of elements.
If you have not already done so, create a sub-directory Lab10 within your Labs directory. This new directory is where you will do work for this lab.
In class we have talked about the insertion sort algorithm. In this
lab you will write an insertion sort for a vector of Fractions. To do
so you will need to read the fractions from the file
~cs203/Labs/Lab10/sample-fracs.dat. The lines in the file
contain numerator and denominator pairs, e.g., 1 2. Make no
assumptions about the number of values in the file.
Copy the files in ~cs203/Labs/Lab10/ into your Lab10
directory. You will have a copy of the Fraction class, a
skeleton for a class called SortedFracs, a main program, a
data file, and a Makefile.
The file SortedFracs.cc contains stubs for the methods that you need to complete. A stub is the simplest form of a method that will compile. It is a common programming practice to create stubs (placeholders) for methods that you need. Then, fill them in one at at time, verifying that the program works at each step. This is the approach you will use in this lab. The program currently compiles but doesn't do much. Type make to compile and then run. After you complete a method, comment out the original cout in each of the stubs.
You will be doing all of your work in SortedFracs.cc. Begin
by completing the method readFromFile(). This method should
open the file sample-fracs.dat, read the fractions and save
them in the vector mFractions. (Use the vector
class' push_back method).
The size() method reports the size of mFractions, and display() will display its contents. Complete these also, compile the program, and convince yourself that it is working properly. Copy into your handin.txt file an execution of your program to demonstrate that the data is being read properly.
When sorting a list of values there must be an ordering for the values
in the list -- in this case the ordering is the ordering of
fractional values. While 
has comparison operators defined for
the basic data types (int, char, etc.), these
comparison operators are not defined for Fraction objects.
It is possible in , however, to extend the definition of an
operator so that it will work for a new type. In our case we want
the operator < to be defined for Fraction objects.
If you look in the file Fraction.cc you will find the
following definition at the end of the file.
bool operator<(const Fraction & inLeft,
const Fraction & inRight) {
return
inLeft.getNumerator()*inRight.getDenominator() <
inLeft.getDenominator()*inRight.getNumerator();
}
This definition treats the operator < as a function with two
parameters -- both Fraction objects -- and returns a
Boolean value.
With this capability to compare Fraction objects, complete the method insertVal(). This method will insert its input parameter at the correct place in the vector so that the vector is sorted. Then change readFromFile() so that it uses insertVal() to insert values into the vector.
Compile the program and run it to convincing yourself that it is working properly. Copy to your handin.txt file a copy of the input file and a copy of the output from your program to demonstrate that the insertion method works.
Implement the writeToFile() method. You should write the fractions to the file sample-fracs2.dat. Use the original file format for writing.
Compile and run the program and make sure it is writing the values correctly. Add to your handin.txt file a copy of the file SortedFracs.cc, a sample run, and a copy of sample-fracs2.dat.
Print (using a2ps, of course) a copy of the handin.txt file you have constructed and turn it in as usual.