Learn OCAML with Real Code Examples

OCaml supports functional programming with first-class functions and pattern matching.

It provides imperative features such as mutable variables and loops.

Modules and functors allow modular, reusable, and composable code.

First-class functions and higher-order programming

Immutable and mutable data structures

Algebraic data types and variants

Exception handling

Powerful module system with signatures and functors

Immutable vs mutable variables

Functions and higher-order functions

Pattern matching and recursion

Lists, arrays, tuples, and records

Modules, signatures, and functors

src/ - OCaml source files

lib/ - reusable libraries

tests/ - unit and integration tests

dune-project - build system config

docs/ - documentation

Write OCaml source code (.ml files)

Compile with ocamlc (bytecode) or ocamlopt (native)

Use dune build system for larger projects

Test code interactively with utop or ocaml REPL

Package reusable code into libraries

Beginner: functional programming basics

Intermediate: modules, pattern matching, recursive data structures

Advanced: functors, polymorphic variants, concurrency

Expert: formal verification, compilers, theorem provers

Research: high-assurance software and static analysis tools

More functional than Java or C#

Stronger type system than Python or JavaScript

Faster native code than interpreted languages

Smaller ecosystem than mainstream languages

Excellent for high-assurance and formal software

1985 – Caml created

1990s – Caml Light and OCaml variants

1996 – OCaml official release

2000s – Type system enhancements and module improvements

2010s+ – Active ecosystem and tooling (OPAM, Dune, Utop)

Let binding: variable or function definition

Pattern matching: control flow based on structure

Functor: parametric module

Module: code encapsulation unit

Tail recursion: recursive call in final position