Project 1--CMPSCI 377 (Fall 2008)

				Worth: 5 points

1 Overview

This project will give you experience writing a simple C++ program
using the STL.

For this assignment, you will write a program in C++ that generates an
"inverted index" of all the words in a list of text files. (See
http://en.wikipedia.org/wiki/Inverted_index for more details.) The
goal of this assignment is to ensure that you are sufficiently up to
speed in C++ to handle the rest of the course. We will also use this 
program in subsequent assignments.


2 Inverter

2.1 Input

Your inverter will take exactly one argument: a file that contains a
list of filenames.  Each filename will appear on a separate line.

Each of the files described in the first file will contain text that
you will build your index from.

For example:

inputs.txt
-----
foo1.txt
foo2.txt

foo1.txt
-----
this is a test. cool.

foo2.txt
-----
this is also a test.
boring.

2.2 Output

Your inverter should print all of the words from all of the inputs, in
"alphabetical" order, followed by the document numbers in which they
appear, in order. For example (note: your program must produce exactly
this output):

a: 0 1
also: 1
boring: 1
cool: 0
is: 0 1
test: 0 1
this: 0 1

Alphabetical is defined as the order according to ascii.  So "The" and
"the" are seperate words, and "The" comes first.  Only certain words
should be indexed.  words are anything that is made up of only alpha
characters, annd not numbers, spaces, etc.  "Th3e" is two words, "Th" and "e".

Your program should absolutely not produce any other output.
Extraneous output, or output formatted incorrectly (extra spaces etc.)
will make the autograder mark your solution as incorrect.  Please leave
yourself extra days to work these problems out.

3 Implementation Hints

Implement the data structure using C++ Standard Template Library (STL)
as a map of sets, as in:

map<string, set<int> > invertedIndex;

Use C++ strings
Code:
#include <string>

and file streams:
#include <fstream>

Remember, your program needs to be robust to errors.  Files may be
empty, etc.  Please handle these cases gracefully and with no extra
output.

The noskipws operator may be useful in parsing the input:
input >> noskipws >> c;

4 Handing Project In

Remember, make sure that your project uses an ifstream, not an fstream.

Your project will be handed in using the autograding system.  Please
see the web page for details on how to submit your solution.