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OCaml

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Description #

OCaml (Objective Caml) is a general-purpose functional programming language with strong type inference, pattern matching, and support for imperative and object-oriented paradigms. It’s known for being expressive, fast, and safe — popular in academia, compiler design, and industrial applications like formal verification and finance.

History #

OCaml originated from Caml, developed in the 1980s at INRIA, the French national research institute. OCaml (Objective Caml) was released in 1996 as an extension with full support for object-oriented programming.

Key milestones:

  • Developed and maintained by the Gallium team at INRIA
  • A major influence on newer languages like F#, ReasonML, and Rust
  • Widely used in formal verification, such as in the Coq proof assistant
  • The Jane Street trading firm uses OCaml for critical financial infrastructure

Hello World Code #

print_endline "Hello, World!";;

How to Run #

Online: #

Locally: #

  1. Install OCaml with OPAM (the package manager):
brew install ocaml        # on macOS  
sudo apt install ocaml    # on Debian/Ubuntu

Save the code in hello.ml

Run:

ocaml hello.ml

Key Concepts #

  • print_endline — outputs a string with a newline
  • Type inference — types are checked but rarely written
  • Immutability — values are immutable by default
  • Pattern matching — expressive control flow
  • Modules and functors — modular architecture
  • Garbage collection — automatic memory management
  • Functional core — pure functions, recursion, no side effects
  • Interoperable — can call C functions and compile to native code
  • REPL support — interactive top-level (REPL) for quick testing
  • Compiles to bytecode or native — flexible performance options

Try It Online #

🔗 Try OCaml
🔗 Replit – OCaml
🔗 OCaml.org Playground

Fun Facts #

  • The “O” in OCaml stands for “Objective”, due to its OO support
  • OCaml is behind financial systems processing billions in trades daily
  • The Coq formal proof assistant is written in OCaml
  • Facebook’s ReasonML and ReScript stem from OCaml
  • Used to teach CS theory in many European universities

Resources #

Updated on June 7, 2025

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