OCaml Development Environment Setup

✔ Prerequisites

Make sure you have the following before you begin.

📅

Operating System

macOS 12+ | Windows 10+

🐳

Docker Desktop

Will be installed in this guide

🛠

Visual Studio Code

Download here

💾

Disk Space

~4 GB free for Docker image

🐳 Step 1: Install Docker Desktop

Select your operating system to see the matching instructions.

🌱 macOS

📱 Windows

🌱

macOS — Install Docker Desktop

Download Docker Desktop
Visit docker.com/products/docker-desktop and download the installer for macOS.

ℸ Choose Apple Silicon if you have an M1/M2/M3/M4 Mac, or Intel for older Macs. Check via > About This Mac.

Install and launch Docker Desktop
Open the downloaded .dmg file, drag Docker to Applications, and launch it. Allow any system permissions when prompted.

Verify Docker is running
Open Terminal and run:

bash

docker --version

You should see a version number like Docker version 27.x.x.

📱

Windows — Install Docker Desktop

Enable WSL 2 (if not already enabled)
Open PowerShell as Administrator and run:

powershell

wsl --install

Restart your computer if prompted.

ℸ WSL 2 (Windows Subsystem for Linux) is required by Docker Desktop on Windows. If you already have WSL 2, skip this step.

Download Docker Desktop
Visit docker.com/products/docker-desktop and download the installer for Windows.

Install and launch Docker Desktop
Run the installer, ensure "Use WSL 2 instead of Hyper-V" is checked, and follow the prompts. Launch Docker Desktop after installation.

Verify Docker is running
Open PowerShell and run:

powershell

docker --version

You should see a version number like Docker version 27.x.x.

🛠 Step 2: Install VS Code Dev Containers Extension

This extension lets VS Code develop directly inside a Docker container.

🔌

Install the Extension

Open Visual Studio Code.

Open the Extensions view
Press Ctrl+Shift+X on Windows/Linux, or Cmd+Shift+X on macOS.

Search for Dev Containers (by Microsoft) and click Install.

🚀 Step 3: Clone the Repository & Open in Dev Container

The assignment repository includes a pre-configured Dev Container. Just clone and open.

📦

Clone the Assignment Repository

Clone the repository
Open a terminal and run:

bash

git clone https://github.com/dgistpl/CSE307-2026spring.git

Open the folder in VS Code

bash

code CSE307-2026spring

Reopen in Container
VS Code will detect the .devcontainer/devcontainer.json file and show a notification:

ℸ “Folder contains a Dev Container configuration file. Reopen folder to develop in a container.”

Click “Reopen in Container”.

Alternatively, open the Command Palette (Ctrl+Shift+P / Cmd+Shift+P) and select:
Dev Containers: Reopen in Container

Wait for the container to build
The first build may take several minutes as Docker downloads the OCaml image and installs tools. Subsequent launches will be fast.

⚠ The initial build may take 10–20 minutes depending on your internet speed. Subsequent launches will be much faster due to Docker caching.

💡 Once the container is running, you have a full OCaml development environment with OCaml 5.2 compiler, utop (interactive REPL), dune (build system), ocaml-lsp-server (code completion, type hints, etc.), and ocamlformat (code formatter).

✅ Verify Your Setup

Run these commands in the VS Code terminal (inside the container) to make sure everything works.

🔍

Check OCaml Version

bash

ocaml --version

Expected output: The OCaml toplevel, version 5.2.x

💬

Try the Interactive REPL (utop)

Launch utop for an interactive OCaml session:

bash

utop

Try typing an expression:

ocaml

List.map (fun x -> x * x) [1; 2; 3; 4; 5];;

Expected output: - : int list = [1; 4; 9; 16; 25]

💡 Press Ctrl+D to exit utop.

🎓

Run a Homework File

You can run OCaml files directly or load them in utop:

bash

# Run an OCaml file directly
ocaml hw1/problem1.ml

# Or load it in utop
utop
# Then type:  #use "hw1/problem1.ml";;

📄 Quick Reference

Useful commands for OCaml development.

Command	What it does
`ocaml file.ml`	Run an OCaml file directly
`utop`	Start the enhanced interactive REPL with auto-completion
`#use "file.ml";;`	Load a file inside utop
`dune build`	Build the project using Dune
`dune exec ./main.exe`	Build and run an executable
`dune test`	Run tests defined in the project
`opam list`	List installed OCaml packages
`opam install <package>`	Install a new OCaml package

🔧 Troubleshooting

Common issues and how to fix them.

Problem	Solution
Docker not running	Make sure Docker Desktop is running before opening VS Code.
Container build fails	Open the Command Palette and select Dev Containers: Rebuild Container.
Permission issues on Linux	Add your user to the docker group: `sudo usermod -aG docker $USER`, then log out and back in.
opam environment not set	Run `eval $(opam env)` in the terminal.