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\begin{center}
\Large \bf CPS08: CD reading/Strings/Streams
\end{center}

You should work on this assignment on mentor.  It is on the acpub system
as well, but you should get used to working on mentor during lab.  It
would be prudent, however, to back things up by ftp-ing files to your
acpub account.

If you can't log into mentor, get help NOW!


\subsection*{Logging in to mentor}

\begin{enumerate}
\item
From an xterm window type {\tt telnet mentor.cs.duke.edu} to connect to
the machine mentor.  You'll be prompted for your login and password so
you should supply these.  If you haven't changed your password from the
default given you, change it now.
To do this, type {\tt passwd}.  You'll be prompted for your
old password and your new password.  After changing your password you
should run the command \verb!~ola/setup! (just type that).  This will
set up your files so that you can work more easily.  You only need to
run the set program once.

\item
Change into your {\tt cps08} 
directory and create a {\tt lab7} subdirectory.  Then
change into this and copy files by typing what's below (don't forget the
trailing dot).
\begin{verbatim}
      cp ~ola/cps08/lab7/* .
\end{verbatim}

If you type {\tt ls} you should see the following files: 
{\tt Makefile}, {\tt cd.dat} and  {\tt cdstuff.cc}.

\item
You need to give your machine permission for mentor to connect to it.
To do this type {\em in an xterm on the DEC station} NOT
in a mentor xterm the following: 
\begin{verbatim}
    xhost +mentor.cs.duke.edu.
\end{verbatim}

Do NOT put a space after the + sign.

\item
You should then be able to type {\tt emacs \&} to get an emacs window.
You want to use the ampersand \& which leaves you with control of your
xterm (so you can run programs from it).

If this doesn't work, skip to the description of {\bf Acpub Alternative}
below for completing the lab on the acpub machines.  You should check
with a TA since all students should have working mentor accounts.

\end{enumerate}

\subsection*{Acpub Alternative}
Change
into your {\tt cps08} 
directory using the {\bf cd} command and create another
directory called {\bf lab7} using the {\bf mkdir} command.
Change into the {\bf lab7} directory. If you did this correctly, when
you type {\bf pwd} you should see a long path name that ends with
{\bf /cps08/lab7.}

You need to copy some files to do this lab.  The {\bf cp} command is
used for copying files on Unix systems.  Type the following 
command to copy files for the lab
(don't forget the trailing period, or dot): 
\begin{verbatim}
      cp ~ola/cps08/lab7/* .
\end{verbatim}

This command will copy all the files in the directory 
\verb!~ola/cps08/lab7! into your {\tt cps08/lab7/} directory.

If you type {\tt ls} you should see the following files: 
{\tt Makefile}, {\tt cd.dat} and  {\tt cdstuff.cc}.

\subsection*{Lab}

Use the emacs commands {\tt C-x C-f} to find/load the file {\sl
cdstuff.cc}.  Then compile this command using {\tt C-x c} and type
{\tt make cdstuff} in the minibuffer.  
In the current version, you'll be prompted for the name of a group.  
The names of all CD's by the artist you type will be printed as well as
the total price of all the CD's.

When testing the program, you must type the name as it's stored in the
file {\tt cd.dat} --- in particular this means that to see titles by the
B-52's youll need to enter the name as ``\verb!B-52's, The!'' (no
quotes)  since this is how the name is stored in the file.

You can check on ``Grateful Dead'', ``Prince'', ``R.E.M'', ``Tone-Loc'',
and many other artists.  Currently, however, you need to run the program
each time the database is searched.  You are to change this so that the
user can query the database many times while the program is running.  

\subsubsection*{Re-reading the file}

To do this, you'll need to put the call to {\tt Lookup} inside a loop.
Prompt the user for a group name, and use some special name to indicate
that no search will be done by the program (the program will stop).  You
might type \verb!"END"!, for example, to indicate that the program is
finished.  In any case, you need to prompt the user.  The prompt should
indicate what sentinel string is used to indicate that the program is
over.

You'll also need to clear the stream since all the entries in the
stream are processed  each time that {\tt Lookup} is called.  
In particular, none of the calls of {\tt GetLine} will succeed after the
file is read completely the first time, because they failed when the
file was exhaustively read the first time.

To fix this, you'll need to use two stream member functions to clear the
stream and reset it to the beginning.

\begin{verbatim}
    input.clear();       // clear any failed flags
    input.seekg(0);      // reset to beginning of stream
\end{verbatim}

You should call BOTH of these to reset the stream to a ``good'' state
so that all of the database can be read.  The best place to
do this is either before the call to {\tt Lookup} or as the first
statements inside {\tt Lookup}.  The function {\tt seekg} is called that
because it ``seeks to get'' a new location.

\subsubsection*{Comparing Strings}

You should also write a function  with the prototype below.

\begin{verbatim}
    String Tolower(String s);
    // postcondition: returns lowercase equivalent of s
\end{verbatim}

that returns a string that is equal to s, except that all uppercase
letters have been converted to lowercase.  
For example, the statement
\begin{verbatim}
    cout << Tolower("HaPpy Days!") << endl;
\end{verbatim}
should print ``{\tt happy days!}'' since uppercase letters are converted
to lowercase (other letters are unchanged).

To do this you'll need to loop over all the characters of s, and you'll
need to use the function {\tt tolower} in \verb!<ctype.h>!.  For
example:
\begin{verbatim}
    String result = "";    // empty string to start
    for(...)
    {
        result += char(tolower(s[k]));
    }
    return result;
\end{verbatim}
is part of the code in {\tt Tolower(String)}.  The cast to a char 
isn't necessary, but it's best to do this with {\tt tolower} since it
returns an int.

Then you should use {\tt Tolower} in the function {\tt Lookup}

\begin{verbatim}
    if (Tolower(group) == Tolower(name))
\end{verbatim}

As a check that everything works, find the total value of all works
by \verb!"various artists"! (it's a lot).


\subsection*{Heart}

If you have more time in lab, you should start working with the
heart monitor program so taht you can ask questions of the TAs.

\subsection*{Submission}

{\bf To turn in programs}: When your modified programs works, you can
submit it, along with a README describing how long it took you and what
your impressions of the lab are.  Submit works on the DEC stations and
on mentor.


\begin{center}
\tt submit08 lab7 cdstuff.cc README
\end{center}

The README file should include your name, how long you worked on the
program, and anyone you received significant help from.  You should also
include any comments you have about the lab.

You should receive a message telling you that the programs were submitted
correctly. 

You should remove (the command is rm) the files {\tt cd.dat} and {\tt
cdstuff}. DON't remove the .cc file.

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