CPSC 427a: Object-Oriented Programming
Michael J. Fischer
September 13, 2011
Remarks on Laboratory Work
This course uses a collection of software tools running under Linux,
including g++, valgrind, eclipse, make, a command shell such as
bash or tcsh, and Linux libraries and header files.
These and other tools you will need are installed and maintained on the
You are all entitled to Zoo accounts for use in this course, and you will all be granted 24-hour access to the Zoo (in Arthur K. Watson Hall). I expect you to use the Zoo for all course work.
For those of you who find it difficult to get to the Zoo and want to work remotely, I offer three suggestions, all of which have some drawbacks.
1. Replicate the Zoo environment on your own machine
This means installing Linux, either in place of your native operating
system, beside it in a dual-boot arrangement, or on top of it using
Drawbacks: It takes time and expertise to install and configure all of the software you will need, and there is still the danger of incompatibilities with the Zoo if you don’t end up with exactly the same versions of everything.
2. Remote login to the Zoo
Log into the Zoo remotely via ssh (which you must install on your
machine), and use command-line tools such as emacs and make to
develop your code.
Drawbacks: People used to program using command-line tools, but it is cumbersome compared with using a modern graphical windowing system and an IDE such as eclipse.
3. Set up a virtual Zoo desktop on your machine
To use VNC (Virtual Network Computing), you must:
See handout 3 (pdf) for detailed instructions.
VNC gives you a virtual Zoo desktop that, in principle,will look and feel
just as if you were sitting at a Zoo console.
Drawbacks: It won’t really feel the same. You will notice delayed response to your mouse actions. It’s a bit of a nuisance getting the connection set up each time you want to work. Moving files back and forth between your local machine and the Zoo requires other tools such as rsync or scp.
Completed homework is to be submitted on the Zoo using the command
In order to submit, you must have a course account.
Put the files you want to submit into a subdirectory, go to that directory,
and run submit.
The first argument to submit is the problem set number.
The remaining arguments are the files to be submitted.
Example: submit 1 * submits everything in the current directory for problem set #1.
Review and Readings
A brief course review to date Lecture 1 describes the course goals of how to construct software that is efficient, robust, scalable, maintainable, reusable, and understandable, as well as giving correct outputs on correct inputs. Lecture 2 looks at how object-oriented design principles can be applied even to C programs, pointing out also inherent limitations of C that motivated the development of C++. Lecture 3 gives a whirlwind tour of an object-oriented C++ program for insertion sort, looking in particular at how the various pieces of code are split into interface or header files (.hpp) and implementation or code files (.cpp).
How to use the textbook
The lectures do not exactly follow the textbook, but they are roughly
For example, lectures 1–3 generally correspond to chapters 1 and 2,
although several concepts from chapters 3 and 4 were also covered
You should read the corresponding chapters carefully, because there is information in the book that will not be covered explicitly in class but that you should nevertheless know.
A Survival Guide for PS1
Operator extensions For PS1, you need to extend three operators <=, <<, and >> to work with type Player.
The corresponding function names are:
Operators extensions are simply new methods for the corresponding functions.
Adding new methods
Every function in C++ may have many methods.
Which method is selected in a function call depends on the number and
types of its arguments, which we call its signature.
Every method must have a distinct signature.
For PS1, the signatures of the methods to be defined are given in Player.hpp.
Two kinds of functions Top-level functions: These are ordinary C-style functions. Member functions: These are functions that belong to a class. When run, the special variable this is an implicit parameter which points to an instance of the class.
Corresponding to the two kinds of functions are two different calling
x becomes the implicit parameter of g(); a the explicit parameter.
An ambiguity with operator extensions
An operator like + invokes its associated function operator+().
But which kind of call does a+b correspond to?
The answer is “both”, with preference given to (2) if the corresponding method is defined.
Operator call example: Top-level function
Operator call example: Member function
Back to PS1
For PS1, the declaration
appears inside of the definition of class Player, so it is a member
appear outside of any class definition, so they are top-level.
Note that the latter are already declared and defined in player.hpp, so you don’t need to do anything more than define the methods read() and print() on which they depend.
More on C++ I/O
Opening and closing streams Some ways of opening a stream.
Can also specify open modes.
To close, use fin.close();.
Simple forms. Assume fin is an open input stream.
Simple forms. Assume fout is an open output stream.
Manipulators are objects that can be arguments of >> or << but do not
necessarily produce data.
Example: cout << hex << x << y << dec << z << endl;
Manipulators are used in place of C formats to control input and output formatting and conversions.
End of file and error handling
I/O functions set status flags after each I/O operation. bad means there was a read or write error on the file I/O. fail means the data was not appropriate to the field, e.g., trying to read a non-numeric character into a numeric variable. eof means that the end of file has been reached. good means that the above three bits are all off.
The whole state can be read with one call to rdstate().
Individual bits can be tested with bad(), fail(), eof(), good().
As in C, correct end of file and error checking require paying close attention to detail of exactly when these state bits are turned on.
To continue after a bit has been set, must call clear() to clear it.