Loops and File I/O - Text Analysis

Due: 0800 next Tuesday

Step 1: Word Count and Average Word Length

In this lab, you're going to do some basic file analysis to some famous books. Download this tarball to a lab04 directory, and untar it with the command

tar xzf books.tgz

Write a program in a file called part1.cpp which prompts the user for a filename of a text file, and prints out the total number of words in the file, as well as the average word length.

The length of a string s can be found with the command s.length(). For example, to read in a string from a user and print out its length, you would run:

string s;
cin >> s;
int lengthOfWord = s.length();
cout << lengthOfWord << endl;

An example run of the program is shown here:

~$ ./part1
Enter a filename: shortExample.txt
Word count: 12
Average word length: 4.3333

~$ ./part1
Enter a filename: prideAndPrejudice.txt
Word count: 124749
Average word length: 4.70193

Warning:

If you have word count 13 for shortExample.txt, you are counting the last word twice! Go back to notes on Class 09 (see the section of "when a file ends") and figure out why, and fix your code!

If you're finished before the lab end, demo to your instructor. Also submit with the command

~/bin/submit -c=IC210 -p=lab04 part1.cpp

Step 2: Sentence Length

We'll assume sentences always end with one of the following:

. ! ?

and that only ends of sentences contain those characters (this may not be entirely accurate, but is good enough for our purposes).

Length of a sentence

For example, the following shows a sentence of length 2.

 Hello World!

In other words, the length of a sentence is the number of words in a sentence.

Your Task

In a file called part2.cpp, augment your solution to part 1 to additionally output the average sentence length.

string::find() function

You can find if a string s contains some string, using find() function. For example, if you want to find if string s has string "he", you can use the command s.find("he").

It will return an int. In particular:

If string "he" does not appear at all, it returns string::npos, which is a predefined very large value.
If it appears somewhere in the string, it returns a value that is different from string::npos. (Technically, the returned value specifies the number of characters over from the left (i.e., position) that string "he" appears, but that's not really important in our context now.)

For example, consider this code:

string s;
cin >> s;
if (s.find("he") == string::npos)
  cout << "Not found..." << endl;
else
  cout << "Found!" << endl;

If string s is "world", the code will output "Not found...". On the other hand, if s is "hello", the code will output "Found!".

So, using this find function, one can check if a string has a "." as follows:

string s;
cin >> s;
if (s.find(".") != string::npos)   // we use != this time 
  cout << "Found!" << endl;
else
  cout << "Not found..." << endl;

Example run

Here is an example run:

~$ ./part2
Enter a filename: prideAndPrejudice.txt
Word count: 124749
Average word length: 4.70193
Average sentence length: 17.1264

If you're finished before the lab end, demo to your instructor. Also submit with the command

~/bin/submit -c=IC210 -p=lab04 part1.cpp part2.cpp

Step 3: Multiple Files

Finally, we'll augment your part 2 solution in a file called part3.cpp so that this will run multiple times, until the filename entered is "quit". For example:

~$ ./part3
Enter a filename: prideAndPrejudice.txt
Word count: 124749
Average word length: 4.70193
Avg sentence length: 17.1264

Enter a filename: shortExample.txt
Word count: 12
Average word length: 4.3333
Avg sentence length: 4

Enter a filename: quit
~$

If you're finished before the lab end, demo to your instructor. Also submit with the command

~/bin/submit -c=IC210 -p=lab04 part1.cpp part2.cpp part3.cpp