University of Waterloo
CS 462/662 - Formal Languages and Parsing
Winter 2016


Tu-Th, 4:00 PM - 5:20 PM, DWE 1515.

Tuesdays will be devoted to lectures. Thursdays will be devoted half to lecture, and half to a problem-solving session in small groups after the first week.


Gregor Richards
Office: DC 2508
Office Hours: Wednesdays at 2-3PM, or by appointment, or just stop by when my office door is open. If my office door is closed, I'm either not in or busy, so please don't knock.

Teaching assistant

Eddie Cheung

Office: DC 3594

Office Hours: Thursdays at 1-2PM


CS 360 or CS 365 or equivalent.


Models of computation such as the Turing machine and the random access machine (RAM) are so powerful that it is quite difficult to prove explicit theorems about what they can and cannot compute.

In the late fifties and early sixties, mathematicians and computer scientists began to study simpler models of computation such as the finite automaton and the pushdown automaton. These models of computation were later found to have many practical applications: regular expressions (used in editing and filename specification); parsing and compiling computer languages; specification (LEX and YACC), etc.

Building on CS 360/365, this course discusses more advanced topics in formal languages and automata theory. Topics that we will discuss include: Thue's problem, the Lyndon theorems, combinatorics on words, closure properties of regular sets, the Myhill-Nerode theorem, ambiguity of CFG's, inherent ambiguity, the Chomsky hierarchy, DCFL's, and other language classes.

We will also cover some "real-life" applications including: phases of compilation, top-down parsing, LL(1) grammars, bottom-up parsing, LR(0) grammars, and LR(k) grammars.


There will be 10 problem sets, with problems of varying difficulty. These will be worth 50% of the mark. You should expect to spend 4-5 hours a week on these problems.

The assignments will be handed out and due as follows:

Assignment Number        Handed Out                      Due
        1		Tuesday, January 12	Tuesday, January 19
        2            	Tuesday, January 19	Tuesday, January 26
        3            	Tuesday, January 26	Tuesday, February 2
        4            	Tuesday, February 2	Tuesday, February 9
        5               Tuesday, February 9	Tuesday, February 23
        6            	Tuesday, February 23	Tuesday, March 1
        7            	Tuesday, March 1	Tuesday, March 8
        8            	Tuesday, March 8	Tuesday, March 15
        9            	Tuesday, March 15	Tuesday, March 22
       10		Tuesday, March 22	Thursday, March 31

Hand your assignments in during class. Late policy: solutions to problem sets will be handed out in the class on the due date; any assignments received after that time will receive no credit. Your single lowest mark out of all 10 assignments will be discarded.

If you have questions about how your assignment was marked, please contact the TA first. If you are still not satisfied, then you can contact the instructor.

There will be no midterm.

There will be a home final exam which is worth 40% of the mark. It will consist of some easy problems and some challenging ones. It may be offered as a take-home final or a traditional final, but in either case, collaboration of any kind is not allowed on the final.

The remaining 10% of the mark will come from the group problem-solving sessions, held on Thursdays. Each student is expected to present the the solution to at least one problem during the term. Your mark will depend on the quality and quantity of problems you present, the clarity of your writeup, and the difficulty of the problems.

Graduate students will be expected to complete a term project in addition to the other work. For graduate students, the mark breakdown will be: problem sets, 40%; final project, 15%; problem-solving session, 10%, and final exam, 35%. The project involves reading papers from the literature about a topic in formal languages or parsing of your choice, and then writing a short (5-15 pages) report on what you have learned.

There is a list of Open Problems related to the course material. Solve any of them and get an automatic 100 for the course!

For the homework problem sets, you are permitted to discuss general aspects of them with other students in the class, but each person should hand in his/her own copy of the solutions. Plagiarism - using outside sources without documentation - will be dealt with severely. Posting problems on Internet bulletin boards, chat groups, newsgroups, etc. and requesting hints or solutions is not permitted.

Any use of outside sources (people, books, articles, etc.) must be documented in anything you hand in for this course. You are welcome to use outside sources, but remember that the goal is to learn: you should try to solve the problems on your own first. When in doubt about whether you need to cite something, err on the side of caution.

The Mathematics Faculty standard penalty for cheating on assignments is a grade of -100% for the assignment, with a minimum deduction of 5% from the final course mark. See the document Cheating and the Student Academic Discipline Policy for more details.

Keeping in Touch.

We'll be using Piazza to distribute information and allow discussion. I will use Piazza to issue corrections and clarifications to homework assignments and the take-home final. Please make sure you're registered. If you're not, email me!

Course marks will be available on LEARN.

The course web page has copies of problem sets, hints for getting better marks, errata for the course textbook, cheating policy, and summaries for every lecture.

Piazza is the most reliable way to contact me. Make questions public unless there is a particular reason to make them private.

Course Text

There is one required text for the course:

There's a little more about the book, including errata, here.