CS2401 Lab Assignment 2


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For this lab I have written a little class that stores numbers, and keeps them in order. The way it does this is with a “reverse bubble sort,” one that starts at the end of the array and works its way to the beginning. The advantage of this is that the new numbers that are added to the back end of the array. (The spot always represented by the variable used.) When a new number is added the bubble sort is able to make one pass through the array and the new number will drop in place.
The problem is that my bubble sort is crashing, and I need you to diagnose why that’s happening and to fix it for me. This I want you to do using gdb. I will also need you to write the load_from_file and write_to_file member functions for me, as well as a main that drives the program.
Start by copying the files from my directory with the command
cp ~jdolan/cs2401/labs/lab2/* .
and remember that the . has to be there. You will find a little class that stores numbers in an array. I have written some of these functions for you, and left a couple for you to write yourself. Your jobs are to:
• Write the implementations for the load_from_file and save_to_file functions.
• Write a main that asks the user for the name of their file. Remember you can read the filename into a string and then use the .c_str() function to use that string in an open command:
o ifs.open(filename.c_str());
The main then:
• loads the array from the file into a NumList object
• Calls the b_sort function on the NumList
• Writes the sorted numbers out to the screen, using the see_all function.

Here there’s a problem. Something goes into an infinite loop. To find this we’re going to use gdb. (I wrote a data file called smaller.dat, so that you wouldn’t have to walk through so much code.) Here are the steps:
• Compile with the –g option (g++ -g *.cc)
• Type gdb a.out
• Type break main
• Type run
• Start hitting n to walk through the code
• When you get to the call of a member function you want to “step into” hit s
• Continue hitting n
Using this method try to find the error that I made in the code that I gave you, and then correct it. When you do, recompile everything and test it. You should see a sorted list of numbers on the screen for either the larger.dat or the smaller.dat file.
Open your main again, and have it asked the user to type in three of their own numbers, which are also inserted into the list. Using the string member functions find (which returns the location of a substr within the string) and the insert function (which will insert a substring at the position sent as its first argument), modify the filename, so that the characters “sorted” are inserted before the dot. (This means that “larger.dat” becomes “largersorted.dat” and “ebenezer.txt” becomes “ebenezersorted.txt” ). Then have the main write the number array out to that file.
After you have successfully compiled all of this run it on the larger.dat file and insert the numbers 106, 237, and 45701.

Submit to your the source code and sorted data file on Blackboard.