G52LAC Languages and Computation

Spring 2017

Further updated version of the G52LAC Lecture Notes now available!

This now covers the entire module.

Solutions to fifth set of coursework released!

Literature Lectures Lecture Links
Coursework Forum
Examination References



A set of lecture notes [ACN17] (PDF), originally developed by Dr. Thorsten Altenkirch and then updated and adapted, support the lectures, along with electronic lecture slides [ELS17] for some of the lectures.

Please note that you should not expect these notes to be a complete or even self-contained record of all that is said and discussed during the lectures. Lecture attendance is compulsory.

The book Introduction to Automata Theory, Languages, and Computation, 3rd edition [HMU3] by John E. Hopcroft, Rajeev Motwani, & Jeffrey D. Ullman is the main reference for the course. Note that this book is quite different from the classic 1979 first edition (see below). Consult the book's web pages for additional supporting material, including additional exercises with automated on-line correction, and errata. The library has got some copies of the book.

There is now also a third edition of this book. This is fine too. However, the page references below are for the second edition.

The 1979 first edition of Introduction to Automata Theory, Languages, and Computation [HU79] by John E. Hopcroft & Jeffrey D. Ullman is very thorough and a classic in the field. However, it is considerably harder than the second and third editions, being aimed more at PhD students or advanced undergraduates. It is now also somewhat difficult to get hold of.

The book An Introduction to Formal Languages and Automata [Lin6] by Peter Linz can be used as an alternative or complement to [HMU3]. The picture shows the sixth edition. Earlier editions should work too. In fact, as the lectures cover standard material, but without following any specific book very closely, there are a range of possible text books for the student who wish to delve deeper into the subject than what the lectures notes [ACN17] do.

One important application area for much of the material covered in the course is compilers. If you are curious, you might want to have a look at the material for the second-year module G52CMP Compilers, or you might want to browse through a book on the topic, such as the classic Compilers: Principles, Techniques, and Tools [ASU86] ("The Dragon book") by Aho, Sethi, & Ullman.


Lecture#DateContentLctr Reading
1 30 Jan Administrative Details and Introduction nhn & vxc [ELS17, Le 1; ACN17, Sec. 1–2; HMU3, Ch. 1]
2 1 Feb Deterministic Finite Automata (DFA) nhn [ACN17, Sec. 3, 3.1; HMU3, Ch. 2, 2.1–2.2]
3 6 Feb Nondeterministic Finite Automata (NFA) nhn [ELS17, Le3; ACN17, Sec. 3, 3.2–3.2.2; HMU3, 2.3–2.3.4]
4 8 Feb Equivalence between NFA and DFA nhn [ELS17, Le 4; ACN17, Sec. 3, 3.2.3; HMU3, 2.3.5–2.4]
5 13 Feb Regular Expressions nhn [ELS17, Le 5; ACN17, Sec. 4, 4.1–4.2; HMU3, Ch.3, 3.1, 3.3]
6 15 Feb Equivalence between Regular Expressions and Finite Automata nhn [ELS17, Le 6; ACN17, Sec. 4, 4.3–4.4; HMU3, 3.2.3]
7 20 Feb Proving Languages not to be Regular vxc [ELS17, Le 7; ACN17, Sec. 6; HMU3, Ch.4, 4.1, 4.2 (only intro)]
8 22 Feb Introduction to Context-Free Grammars (CFG) nhn [ELS17, Le 8; ACN17, Sec. 7, 7.1; HMU3, Ch.5, 5.1–5.1.4, 5.3]
9 27 Feb The Language of a CFG nhn [ELS17, Le 9; ACN17, Sec.7, 7.2–7.3; HMU3, 5.1.5–5.1.7]
10 1 Mar Derivation Trees and Ambiguity nhn [ELS17, Le 10; ACN17, Sec. 7, 7.4–7.5; HMU3, 5.2, 5.4–5.4.1, 5.1.4, 5.4.3–5.4.5]
11 6 Mar Disambiguating Context-Free Grammars vxc [ELS17, Le 11; ACN17, Sec. 7, 7.5; HMU3, 5.4.2]
12 8 Mar Recursive-Descent Parsing: Introduction nhn [ELS17, Le 12; ACN17, pp. ??–??; HMU3, 5.3.1-5.3.2]
13 13 Mar Recursive-Descent Parsing: Elimination of Left Recursion vxc [ELS17, Le 13; ACN17 pp. ??–??]
14 15 Mar Recursive-Descent Parsing: Predictive Parsing nhn [ELS17, Le 14; ACN17 pp. ??–??]
15 20 Mar Turing Machines vxc [ELS17, Le 15; ACN17, Sec.9, 9.1–9.2; HMU3, Ch.8, 8.2]
16 22 Mar λ-Calculus vxc [ELS17, Le 16; ACN17, Sec.10]
17 27 Mar The Church-Turing Thesis vxc [ELS17, Le 17; ACN17, pp.98–101; HMU3, 8.2.1; Lin6, Ch.13 only intro]
18 29 Mar Decidability and the Halting Problem vxc [ELS17, Le 18; ACN17, pp. 90–91; HMU3, Ch.9, Lin6, Ch.12]
19 3 Apr Computational Complexity vxc [ELS17, Le 19; ACN17, pp. ??–??; HMU3, Ch.10; Lin6, Ch.13]
20 5 Apr The P vs NP Problem vxc [ELS17, Le 20; ACN17, pp. ??–??; HMU3, Ch.10; Lin6, Ch.14]

Lecture Links

Copies of electronic slides, any major pieces of program code, other electronic material used during the lectures, and useful links can be found here.


The coursework consists of five problem sets. The average of the best four counts for 25 % of the overall mark for the module. The issue and submission dates are as follows:

Problem Set#Issue DateSubmission Date
1 (for lect. 1–2) 1 Feb 8 Feb
2 (for lect. 3–7) 22 Feb 1 Mar
3 (for lect. 8–14) 15 Mar 22 Mar
4 (for lect. 15–16) 22 Mar 29 Mar
5 (for lect. 17–20) 5 Apr 10 May

The deadline for submitting solutions is 3 PM on the submission date. Solutions are to be submitted to the Student Service Centre as handwritten (recommended) or typeset hard copies. Model solutions will normally be released shortly after the deadline. Marks will be released through Moodle and marked solutions will be returned via the Student Service Centre.

To make quick marking and feedback possible, and as model solutions will be released shortly after the submission deadline, late submissions will not be considered. Extenuating circumstances affecting a single problem set are addressed by the rule that only the four best solutions count. In case of valid extenuating circumstances affecting two or more of the problem sets, suitable arrangements will be made.

Problem sets below. Model solutions will be added shortly after the deadlines.

G52LAC Moodle Forum

A Moodle Forum for G52LAC has been set up.

The forum is intended for asking questions about and discussing aspects of G52LAC, like the coursework. It will be monitored by the G52LAC team, and we'll endeavour to answer any outstanding questions reasonably quickly. However, any one is free to contribute to the discussions and help with answering questions. Indeed, in the spirit of an on-line forum, you are encouraged to do so!

Of course, we do ask that you do not post the exact solutions to the coursework! The point of the coursework is that you should ultimately solve the problems yourselves so that you know what you have understood and what you need to work more on or ask about.


Some basic information about the exam:

In the case of a resit examination:

The style of the exam will be similar to the ones given for G52MAL over the past few years, such as the ones below. However, not all questions are necessarily relevant as some topics (such as minimisation of DFAs) are not covered in G52LAC. On the other hand, there are also some new topics such as the λ-Calculus and computational complexity. Use the material covered in the lectures as a guide. Note that there is not going to be any choice regarding which questions to answer: all questions will be compulsory.

Model solutions for some past exams:


Last updated 5 April 2017.