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Language Manual

Read the language manual to get a deeper understanding!
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Papers

Aspiring towards greater understanding of the language? Want to push the limits and discover brand new things? Check out papers written by leading OCaml researchers:
Eff Directly in OCaml
The language Eff is an OCaml-like language serving as a prototype implementation of the theory of algebraic effects, intended for experimentation with algebraic effects on a large scale. We present the embedding of Eff into OCaml, using the library of delimited continuations or the Multicore OCaml branch. We demonstrate the correctness of the embedding denotationally, relying on the tagless-final-style interpreter-based denotational semantics, including the novel, direct denotational semantics of multi-prompt delimited control. The embedding is systematic, lightweight, performant, and supports even higher-order, 'dynamic' effects with their polymorphism. OCaml thus may be regarded as another implementation of Eff, broadening the scope and appeal of that language.
Oleg Kiselyov, KC Sivaramakrishnan
ocaml-workshop
core
language
A Memory Model for Multicore OCaml
We propose a memory model for OCaml, broadly following the design of axiomatic memory models for languages such as C++ and Java, but with a number of differences to provide stronger guarantees and easier reasoning to the programmer, at the expense of not admitting every possible optimisation.
Stephen Dolan, KC Sivaramakrishnan
ocaml-workshop
multicore
Extending OCaml's `open`
We propose a harmonious extension of OCaml's `open` construct. OCaml's existing construct `open M` imports the names exported by the module `M` into the current scope. At present `M` is required to be the path to a module. We propose extending `open` to instead accept an arbitrary module expression, making it possible to succinctly address a number of existing scope-related difficulties that arise when writing OCaml programs.
Runhang Li, Jeremy Yallop
ocaml-workshop
core
language

Releases

The history of OCaml releases with a summary and a complete changelog, as well as the manual at that time.
Recent Release

4.14.0 (2022-03-28)

Some of the highlights in OCaml 4.14.0 are:

  • Integrated support for "go to definitions" in Merlin.
  • Standard library: new modules In_channel and Out_channel, many new functions in Seq module, UTF decoding and validation support for strings and bytes.
  • Runtime optimisation: GC prefetching. Benchmarks show a speedup of around 20% in GC-heavy programs.
  • Improved error messages in particular for module-level error.
  • Deprecated functions and modules in preparation for OCaml 5. In particular, the Stream and Genlex modules are now deprecated.
  • Type variables can be explicitly introduced in value and variant constructor declarations. For instance, 
        val fold: ('acc -> 'elt -> 'acc) -> 'acc -> 'elt list -> 'acc
    type showable = Show: 'a * ('a -> string) -> showable
    can now be written as 
        val fold: 'acc 'elt. ('acc -> 'elt -> 'acc) -> 'acc -> 'elt list -> 'acc
    type showable = Show: 'a. 'a * ('a -> string) -> showable
  • Tail-call with up to 64 arguments are now guaranteed to be optimized for all architectures.
  • Experimental tail modulo cons (TMC) transformation

Recommended Books

What experts programmers and researchers are saying about OCaml, from the beginner level to the more advanced topics.
More OCaml: Algorithms, Methods & Diversions cover
More OCaml: Algorithms, Methods & Diversions
 OCaml From the Very Beginning cover
OCaml From the Very Beginning
 Real World OCaml cover
Real World OCaml