# EECS 598: Category Theory for Computer Scientists

- Lecture: Tuesday & Thursday, 9:30-11:30, 2153 G.G. Brown Laboratories
- Instructor: Max S. New
- Office: Beyster 4640
- uniqname: maxsnew
- Office Hours: Monday & Wednesday 4-5:30pm, remote and Beyster 4640
- Canvas
- Piazza

This graduate-level course is an introduction to category theory for computer scientists. Category theory is a branch of algebra that studies structures abstracting function composition. This field of abstract mathematics has found many uses in the theory of programming languages, especially typed functional programming and design and implementation of proof assistants. Our goal in this course is to get a basic understanding of category theory sufficient to understand applications in the theory of programming languages.

## Course Materials

The primary text is Steve Awodeyâ€™s Category Theory, 2nd Edition.

We will also use as supplementary material, the freely available texts Category Theory in Context by Emily Riehl and Categorical Logic from a Categorical Point of View by Michael Shulman.

## Office Hours

Office hours will be held twice weekly, on Mondays and Wednesdays from 4-5:30pm. Unless otherwise specified, these will be hybrid remote and in-person in my office at Beyster 4640. Either way, you should use the queuing system.

## Evaluation

Your grade in the course will primarily be based on the homework assignments, given out every 1-2 weeks. Homeworks will unless otherwise stated be problem sets to be completed either handwritten or in pdf format, preferably using LaTeX. You will be graded on correctness and clarity of your work. Homeworks can be done in groups of two. You should not discuss your homework with anyone besides your partner and the instructor.

*Late homeworks will not be accepted*. If you need an extension talk to the professor. However the lowest two homework grades will be dropped.

The next major portion of your grade will be an in-class presentation of homework solutions at the end of certain lectures. These will start once the first homework is due. At the end of each class one or more students will present a solution from the previous assignment to the class.

Lectures will be recorded using lecture capture, available to be accessed on Canvas. I encourage you to attend class in person if possible. You will get much more out of the course if you attend and ask questions in class.

The precise breakdown of grading is as follows

Activity | Percentage of final grade |
---|---|

Problem Sets | 80 |

In-class presentation | 20 |

## Schedule of Topics

Below is a tentative schedule of topics and associated readings for the semester. Besides the first lecture, you are expected to read the assigned readings *prior to* lecture.

Meeting Date | Topic | Assigned Readings | HW |
---|---|---|---|

Thu, Jan 6 | Course Overview, what is Category theory? | Awodey Ch 1.1-1.3, Riehl Examples 1.1.3 and 1.1.4 | |

Tue, Jan 11 | More Examples of Categories | Awodey Ch 1.4, Riehl Examples 1.3.2 | |

Thu, Jan 13 | Isomorphisms and Constructing Categories | Awodey Ch 1.5-1.6 | PS 1 out, PS1 LaTeX |

Tue, Jan 18 | Free Categories as Syntax | Awodey Ch 1.7, Shulman Ch. 0, Ch. 1.1-1.2 | |

Thu, Jan 20 | Epimorphisms/monomorphisms | Awodey Ch 2.1-2.3 | PS 2 out, PS2 LaTeX |

Tue, Jan 25 | Initial/Terminal Objects | Awodey Ch 2.4-2.7, | |

Thu, Jan 27 | Products | PS 3 out, PS3 LaTeX | |

Tue Feb 1 | Duality, Initial Objects | Awodey Ch 3.1-3.2 | |

Thu Feb 3 | Syntax for Free Categories with X | Shulman Ch 1.4-1.6 | |

Tue Feb 8 | (Co-)Equalizers | Awodey Ch 3.3 | PS 4 out, PS4 LaTeX |

Thu, Feb 10 | Subobjects & Pullbacks | Awodey Ch 5.1-3 | |

Tue Feb 15 | Limits and Colimits | Awodey Ch 5.4-5.6 | |

Thu Feb 17 | Exponentials | Awodey Ch 6.1-6.2 | |

Tue Feb 22 | Cartesian Closed Categories in CS | Awodey Ch 6.3-6.6 | |

Thu Feb 24 | Cartesian Multicategories | Shulman Ch 2 | |

Tue Mar 8 | Category of Categories | Awodey Ch 7.1-7.2 | PS 5 out, PS5 LaTeX |

Thu Mar 10 | Natural Transformations | Awodey Ch 7.4-7.5 | |

Tue Mar 15 | Functor Categories, Monoidal Categories | Awodey Ch 7.7-7.8 | |

Thu Mar 17 | Equivalence of Categories | Awodey Ch 7.9-7.10 | PS 6 out, PS6 LaTeX |

Tue Mar 22 | Presheaves | Awodey 8.1-8.4 | |

Thu Mar 24 | Yoneda Lemma | Awodey 8.3-8.4 | |

Tue Mar 29 | Higher-order Logic | Awodey 8.8 | |

Thu, Mar 31 | Adjunctions | Awodey 9.1-9.2 | |

Tue Apr 12 | Adjoints and Limits, Monads I | Awodey 9.6 | PS 7 out, PS7 LaTeX |

Thu Apr 14 | Monads II | Moggi | |

Tue Apr 19 | Category Theory in Haskell | Wadler | PS 8 out, PS8 LaTeX |