Jason Hickey - Real world OCaml

• Garbage collection for automatic memory management, now a feature of almost every modern, high-level language.

• First-class functions that can be passed around like ordinary values, as seen in JavaScript, Common Lisp, and C#.

• Static type-checking to increase performance and reduce the number of runtime errors, as found in Java and C#.

• Parametric polymorphism , which enables the construction of abstractions that work across different data types, similar to generics in Java and C# and templates in C++.

• Good support for immutable programming , i.e., programming without making destructive updates to data structures. This is present in traditional functional languages like Scheme, and is also found in distributed, big-data frameworks like Hadoop.

• Automatic type inference to avoid having to laboriously define the type of every single variable in a program and instead have them inferred based on how a value is used. Available in a limited form in C# with implicitly typed local variables, and in C++11 with its auto keyword.

• Algebraic data types and pattern matching to define and manipulate complex data structures. Available in Scala and F#.

OCaml was written in 1996 by Xavier Leroy, Jrme Vouillon, Damien Doligez, and Didier Rmy at INRIA in France. It was inspired by a long line of research into ML starting in the 1960s, and continues to have deep links to the academic community.

ML was originally the meta language of the LCF (Logic for Computable Functions) proof assistant released by Robin Milner in 1972 (at Stanford, and later at Cambridge). ML was turned into a compiler in order to make it easier to use LCF on different machines, and it was gradually turned into a full-fledged system of its own by the 1980s.

The first implementation of Caml appeared in 1987. It was created by Ascnder Surez and later continued by Pierre Weis and Michel Mauny. In 1990, Xavier Leroy and Damien Doligez built a new implementation called Caml Light that was based on a bytecode interpreter with a fast, sequential garbage collector. Over the next few years useful libraries appeared, such as Michel Maunys syntax manipulation tools, and this helped promote the use of Caml in education and research teams.

Xavier Leroy continued extending Caml Light with new features, which resulted in the 1995 release of Caml Special Light. This improved the executable efficiency significantly by adding a fast native code compiler that made Camls performance competitive with mainstream languages such as C++. A module system inspired by Standard ML also provided powerful facilities for abstraction and made larger-scale programs easier to construct.

The modern OCaml emerged in 1996, when a powerful and elegant object system was implemented by Didier Rmy and Jrme Vouillon. This object system was notable for supporting many common object-oriented idioms in a statically type-safe way, whereas the same idioms required runtime checks in languages such as C++ or Java. In 2000, Jacques Garrigue extended OCaml with several new features such as polymorphic methods, variants, and labeled and optional arguments.

The last decade has seen OCaml attract a significant user base, and language improvements have been steadily added to support the growing commercial and academic codebases. First-class modules, Generalized Algebraic Data Types (GADTs), and dynamic linking have improved the flexibility of the language. There is also fast native code support for x86_64, ARM, PowerPC, and Sparc, making OCaml a good choice for systems where resource usage, predictability, and performance all matter.