Cornell CS 3110: Data Structures and Functional Programming
CS 3110 is Cornell's famous functional-programming and data-structures course, taught in OCaml. It covers immutability, recursion, higher-order functions, modules and functors, formal specification and verification, and reasoning about correctness and complexity. It's a required CS core course and a notorious pace step-up after CS 2110.
Fennie is independent and not affiliated with Cornell University. This is an unofficial study guide.
What makes it hard
The functional paradigm forces a genuine rewiring: no loops or mutation, problems solved by recursion and higher-order functions, and a type system that rejects code until it's right. The module/functor system and formal reasoning are conceptually dense, the assignments are long and unforgiving, and prelims test writing and reasoning about OCaml by hand, so the students who fall behind rarely recover.
What you'll cover
- • OCaml and functional programming
- • Recursion and higher-order functions
- • Immutable data structures
- • Modules and functors
- • Formal specification and verification
- • Reasoning about correctness and complexity
The CS 3110 study guide
How to study for Cornell CS 3110, step by step.
- 1
Rewire into the functional mindset deliberately
Fighting OCaml by simulating loops and mutation is the classic CS 3110 mistake. Embrace recursion and higher-order functions as the primary tools from day one. The paradigm shift is the actual learning, not a side effect.
- 2
Let the type system teach you
OCaml's compiler rejects code until the types line up, and its messages are dense at first. Read them as guidance rather than noise; understanding a type error is usually understanding your bug.
- 3
Practice writing OCaml by hand
Prelims test producing and reasoning about functional code without a compiler. Write functions on paper and reason about their types and behavior, because the editor's safety net is gone on exams.
- 4
Start the long assignments immediately
CS 3110 assignments are long and the debugging is conceptual, not mechanical. Begin the day of release. The gap between early starters and deadline coders is brutal here, and the curve reflects it.
- 5
Internalize modules and verification, don't memorize
Functors and formal specification are dense and build on each other. Work small examples until the ideas are intuitive, since prelim questions test understanding you can't fake by recall.
Today
Today's CS 3110 plan
What a Fennie Daily Plan looks like for CS 3110. Yours is built from your own syllabus and adapts every day to your deadlines and progress.
First plan free, no card required. Fennie is independent and unaffiliated with your school.
FAQ
Is CS 3110 at Cornell hard?
It's one of the toughest required CS courses, mainly because the functional paradigm in OCaml rewires how you solve problems: no loops or mutation, everything recursion and higher-order functions. Long assignments and formal reasoning compound it, so falling behind is costly.
Why does CS 3110 use OCaml?
OCaml makes functional programming, an expressive type system, and formal reasoning first-class, which is the whole point of the course: learning to think about programs as specifications and proofs, not just instructions. The language is a teaching tool for those ideas.
How do I prepare for CS 3110?
Come in with CS 2110's recursion and data structures genuinely solid, then commit to learning the functional mindset rather than fighting it. Start assignments the day they drop and practice writing OCaml by hand, since prelims have no compiler.
More Cornell courses
CS 1110: Introduction to Computing: A Design and Development Perspective
CS 1110 is Cornell's Python-based first programming course, covering variables and types, functions, conditionals and loops, objects and classes, recursion, and testing. It's taken by intended CS majors and a large non-major population alike, and it leads into CS 2110 for those continuing in the major.
CS 2110: Object-Oriented Programming and Data Structures
CS 2110 is Cornell's second programming course, taught in Java and cross-listed as ENGRD 2110. It covers object-oriented design, data structures (lists, trees, hash tables, graphs), recursion, and an introduction to algorithmic analysis. It's the gateway most CS and engineering students name as the major's first real workload jump.
CS 2800: Discrete Structures
CS 2800 is Cornell's discrete mathematics course for CS majors, covering logic and proof, induction, sets, functions and relations, combinatorics, graph theory, basic probability, and finite-state machines. It's the bridge from coding to the mathematical reasoning the upper-level theory courses assume.
CS 4820: Introduction to Analysis of Algorithms
CS 4820 is Cornell's upper-level algorithms course, covering greedy algorithms, divide and conquer, dynamic programming, network flow, and NP-completeness and reductions, with a heavy emphasis on proving correctness and analyzing complexity. It's a required CS core course and a capstone of the theory sequence.