CS 127 Spelling Checker

Note: Changes have been made to this assignment to clean it up for re-use later (11/2/01).

Design document due Friday, 10/19/01
Project due Due Wednesday, 10/24/01

The Assignment

For this assignment you will write a spell checker, by storing a dictionary as a sorted list of words. Its structure, in pseudocode, might look like this:

        Open the dictionary file.
        For each word in the dictionary
           add the word to the list.
        Close the dictionary file.

        Open the big monster text file.
        For each word in the BMTF
           make proper adjustments to case of letters.
           search the list for the word.
           if word is misspelled, store it.
        Close the BMTF.

        Display all misspelled words to the screen in alphabetical order.

Note that many of these pseudocode lines will be handled by function calls in the real code.

The Dictionary

The central purpose of this assignment is to write an application which uses binary search. While you're debugging and testing your code at first, MAKE SURE to use a small dictionary file and a small text file. Otherwise, you'll put too much strain on our servers. Later, you'll need to try it on big files. I've placed a big dictionary in the file /Accounts/courses/cs127/dmusican/web2.txt . Try the UNIX command "wc" on it, and you will discover that this dictionary has 234,936 words in it. The words are already sorted, and one per line. You will need to build the dictionary in memory, and be able to search for a word in the dictionary using binary search..

The Input

You should not use standard input (cin) to obtain either of the files. Your program should ask the user for the location of the dictionary and the location of the document to be checked.

Capital letters, punctuation, and all that jazz

The dictionary mentioned above contains words with upper and lower case letters.

In order to keep this problem from becoming a terribly tedious exercise in details, you should use the following over-simplified rules.

Punctuation:

You should remove all punctuation from a word before checking its spelling.
This includes apostrophes (') and hyphens (-), even if such words appear in the dictionary with those symbols in them.
"can't" should be checked as "cant"
"do#g" should be checked as "dog"
"proto-human" should be checked as "protohuman".

If a word in your document is not at the beginning of a sentence:

Its spelling must match a word in the dictionary with exactly the same capitalization in order to be spelled correctly.
If the dictionary contains "Zeus" and your document contains the word "zeus", your word is misspelled.
If the dictionary contains the word "person" and your document contains the word "Person" (not at the beginning of a sentence), your word is misspelled.
You should report the word to the user with precisely the same capitalization as it appears in the document.

If a word in your document is at the beginning of a sentence:

There are two possible ways the word can match the dictionary to be considered correctly spelled.
The first way is to match the word exactly.
The second way is to change the first letter of your word to lower case, and then see if it matches the dictionary.
If the first word of your sentence is "The", your word is spelled correctly.
If the first word of your sentence is "the", it is also spelled correctly.
If the first word of your sentence is "Geblotnik", it is not spelled correctly.
Any word that follows a period is assumed to be the first word of a sentence.
The first word of your document is also considered to be the first word of a sentence.
You should report the word to the user with precisely the same capitalization as it appears in the document.

The Output

You should list all misspelled words to the screen in alphabetical order.

Each misspelled word should only be listed once.
You may use any sorting algorithm you like - you do not need to be fancy here (unless you want to be).
You should sort all the words lexicographically, including words with capital letters.
Words starting with capital letters should appear before words appearing with lower case letters.

Implementation Details

You will need to decide how to store the dictionary and the misspelled words. They're both rather similar in that they both store sorted strings. On the other hand, the dictionary is static whereas the misspelled words are dynamic. Choose appropriate data structures to deal with each of the two situations. Justify your decision with documentation in your code.