CECS 524 
Lempel-Ziv Compression using ETS

The Lempel-Ziv-Welch Compression article, linked from the class site, 
explains the algorithm. Write a function to compress text to binary using 
this algorithm and another to decode binary to text.Compare the sizes of 
the compressed file and the original.  Of course compare the sizes of the 
decoded file and the original and see that they are the same. You can use 
16-bit codes so when you have added 65,000 codes then do not add 
any more. (Optionally you could reduce the size of the file by using 
variable size codes starting with 7 bits for the 128 ASCII characters.) 
Use an ETS table to hold the codes.  Start the table with the 
single character from 0 to 127 having that number as its code. Remember 
that strings are lists of integers so [65] would be the way to represent 
"A" and {[65],65} would be the tuple to add into ETS.

My program takes a page and a half exclusive of comments and has four 
functions. 

Although not part of this assignment it would be interesting to 
investigate parallel compression. The article Parallel Lempel Ziv Coding, 
linked from the class site, has some ideas. ETS may not be appropriate 
for parallel compression if the table is shared among processes.