There is a small mistake with the complete.output file. In particular the second time s4 is printed out is should be:

 s4 = "ng
"

   cin >> s3 >> s4;

The complete.output file has been updated to reflect the "correct" answer.

The reason the original complete.output file contained the answer that it did was because the program used to generate it MODIFIED the DELIMITER character of s4 to be the newline character when the following statement was executed:

   s4 = (str1 + " " + str2);

Please re-read the course syllabus regarding email policies. Although it may not have been explicitly stated, DO NOT EMAIL PROJECT QUESTIONS AS THEY WILL GO UNANSWERED - if you have a question you must see someone in person during the posted office hours - even if it is the weekend or 2am in the morning - in which case you will need to remain patient, work on other parts of the project, study other material, work on other classes, or take a break. The course syllabus states that the email addresses of the instructional staff [this includes the TAs] are provided for emergency situations only.

So far several people have sent email about the project, most with "what if" or "can I" type questions:

1. Can I add a data member to the DoubleStack or MyString class? Answer: This is addressed in the header files.
2. Can I add a friend function to the either class? Answer: The header file states you may add private member functions and that you may not modify the header file in any other way.
3. What if someone tries to print out a DoubleStack using << or to pass an array of characters to the DoubleStack ctor? Answer: you were not asked to handle these cases and given the header file provided you have no way to handle these cases as the only way to do so would be to modify the header file (see prior questions).

Note: all students should strive to submit projects well PRIOR to the 11pm due time and if you are unable to, then fortunately you have up to 48 hours to fix whatever problems may have kept you from submitting ontime. Due to the fact that students are given ample opportunity to meet with the instructional staff prior to a project being due, no question regarding a project is considered an emergency situation. An emergency situation would be if the class computer accounts were encountering problems - if something like that does occur you should check the class webpage (click on the announcements link and the FAQ page for the respective project) and if the problem is not mentioned there, then and only then should you notify the instructional staff.

Additionally, email is perhaps one of the worst mediums/means for holding a conversation and many people think that it is an instant medium. When adequately answering a question a conversation is generally needed. Additionally, in the past there have been MANY instances where someone asks a question via email (like "the compiler gives me this weird error ... what is wrong?") and by the time someone answers (assuming there is even enough information provided to give a decent answer) the person has already figured out the problem and responds back saying something to the effect of "Thanks but I already figured it out, however there is a new error which says ... can you help me?" !!!!

So the next concern might be to ask about a clarifying question or a yes/no type of question - this is where the instant medium becomes an issue - 1) we do not have the resources to satisfy the instant wants of everyone and 2) it is not best to do so - rather than "fire off" (send off) an email everytime a little question pops up (like can I do this, what if this, how do I fix this, ...) students should learn to think about their problem/question first and see if they themselves can either 1) answer the question or 2) look up an answer to the question (without violating the honor code). This is perhaps the most important of items - attempting to think about the problem (do I absolutely have to modify the header file, or is there any other way I could do this that works per the project specifications? OR It appears that I am having difficulty with the std:: portion of the code - when do I need std:: and when do I not?, ...).

It turns out that this is possible (using a special const_cast) HOWEVER you do not have to worry about copying this part of the MyString on the right hand side (of the = (assignment) operator) into the MyString object on the left hand side (just copy the string/linked list portion over).

Also with the operator+ function (which concatenates two MyStrings together to create a new MyString object) it doesn't matter what delimiter character the resulting MyString (which is returned) has (meaning we won't test to see what delimiter it has).

Note: A lot of project #0 uses the concept of operator overloading which allows someone to modify the built in operators (like + for example) to work with User Defined Objects (classes).

Hopefully most people are familiar with the concept of a stack, however if you are not the following will help both describe how a stack works and in particular a "DoubleStack" (which is just a minor "enhancement" over a basic stack).

One important note: the "push" (operator+) and "pop" (operator--) functions of the DoubleStack class should NOT perform ANY dynamic memory allocations or deletions - repeat do NOT delete or create any dynamic memory in the "push" or "pop" operators.

In general STACKs are implemented using an array of items. Items can be pushed (aka added) onto the top of a stack and then popped (aka removed) off of the stack (but only from the top). In this project a DoubleStack (using the default ctor) starts out empty HOWEVER has enough space for up to 100 items (the size) and the data component would look like this (a pointer to a 100 element array of characters which is initially "empty"):

            0   1   2   3   4     ...     95  96  97  98  99   <--- these are the indexes of the array
data ---> +---+---+---+---+---+---------+---+---+---+---+---+
          |   |   |   |   |   |   ...   |   |   |   |   |   |
          +---+---+---+---+---+---------+---+---+---+---+---+
        ^                                                      ^
        |                                                      |
       top1                                                   top2

For example if we push the characters A, ?, and f onto the "bottom" stack like follows:

   DoubleStack ds;
   'A' + ds;
   '?' + ds;
   ds + '$';   // pushing onto the "top" stack
   'f' + ds;

            0   1   2   3   4     ...     95  96  97  98  99
data ---> +---+---+---+---+---+---------+---+---+---+---+---+
          | A | ? | f |   |   |   ...   |   |   |   |   | $ |
          +---+---+---+---+---+---------+---+---+---+---+---+
                    ^                                     ^
                    |                                     |
                   top1                                  top2

   --ds;       // pops one item off the "bottom" stack and returns a copy of it
   '(' + ds;
   '0' + ds;

            0   1   2   3   4     ...     95  96  97  98  99
data ---> +---+---+---+---+---+---------+---+---+---+---+---+
          | A | ? | ( | 0 |   |   ...   |   |   |   |   | $ |
          +---+---+---+---+---+---------+---+---+---+---+---+
                        ^                                 ^
                        |                                 |
                       top1                              top2

Hardcoding is when someone puts cout statements in their code to print out portions of the sample output(s). For example in project #0 if someone had modified the main.cpp main function to have a print statement such as:

   cout << "zyxwvutsrq" << endl;
   cout << "ABC" << endl;

Another small "tip for success" is to develop (write) your code one piece at a time and thoroughly test each piece as you write it. Amazingly we see students in office hours who spent hours writing all of the code and then didn't start testing it until after they had most of their code written - even the best programmers out there generally aren't that brave!

You should start with the most essential functions (typically the ctor's and dtor and a print function) and write those and then test them:

int main() {
   MyString s1( '*' );
   cout << "'" << s1 << "'" << endl;
   return 0;
}

int main() {
   string str( "testing" );
   HugeInt s1( str );
   cout << s1 << endl;
   return 0;
}

When you come to see someone in office hours for help on your project, you should always bring a current printout of your code and if possible a printout of the compiler error messages (if there are any) and if it compiles a printout of the programs output (and the input used to generate that output). If you want to get the output of the compilers error messages you will need to redirect error output as follows:

%  make  >&  my.comp.errors

Having the requested information above will assist the instructional staff in being better able to assist you and others who are waiting to be assisted. Please also understand that the office hour room is a shared resource with other classes and we ask that you be respectful of the room and others using the room.

Another VERY IMPORTANT thing to do prior to going to office hours is attempt to "debug" your code as much as possible when you have a problem and that way when you see the TA you can point to the line (or lines) of code causing the problem (it should typically only be one line) and explain to them what the problem is and hopefully they will be able to figure out the problem (and a solution) and explain it to you so that you can determine how to fix it. When "debugging" code you can either attempt to use a debugger (see the tutorials in the posting account) or just use good old fashion debug cout (or cerr) statements:

    cout << "GOT THIS FAR" << endl;  // very important to use endl;
    someFunctionCall();
    cout << "DIDN'T GET THIS FAR" << endl;  // and cout is recommended over cerr

A FAQ is a list of Frequently Asked Questions and in particular the FAQ's for projects in this class will have questions listed in reverse chronological order (meaning the most recent question will appear at the top of the FAQ list and the first question asked/answered will appear at the bottom of the list).