OCaml (Objective Caml) is a functional programming language that extends ML with object-oriented features. Created at INRIA in France, it combines functional programming’s elegance with practical performance and has influenced languages from Rust to F#.
Origins
Xavier Leroy led the development of OCaml at INRIA, building on earlier work on Caml. The goal was to create a practical, efficient functional language suitable for real-world software development.
Key Features
OCaml combines functional programming with pragmatic features:
- Strong type inference: Rarely need explicit type annotations
- Pattern matching: Elegant handling of algebraic data types
- Efficient compilation: Native code performance rivaling C
- Object system: Classes and objects when needed
- Module system: Sophisticated code organization
- Polymorphic variants: Flexible extensible types
Notable Uses
OCaml powers significant projects:
- Jane Street: Major financial firm uses OCaml extensively
- Facebook/Meta: Used for Hack type checker and Flow
- Coq: Proof assistant written in OCaml
- MirageOS: Unikernel operating system
Influence
OCaml’s ideas spread to other languages:
- F#: Microsoft’s .NET ML dialect based on OCaml
- Rust: Pattern matching and type system influenced by OCaml
- Reason: Facebook’s alternative syntax for OCaml
- ReScript: OCaml-based JavaScript compiler