Objective Caml

ppx and extension points

The release of OCaml 4.02 is approaching and amongst many other new stuff, it will include the work on -ppx and extension points, supporting light-weight syntactic tools (without Camlp4). This effort was coordinated with the OCaml community through the wg-camlp4 mailing list, and now it is very enjoyable to see the community starting to make good use of these new features. In this post, I wanted to collect pointers to blogs and projects making use of extension points.

Inlined records in constructors

I'd like to introduce a new language feature, inlined record arguments on constructors, which I propose for inclusion in OCaml. In a nutshell, it allows you to define a record directly within a sum type constructor:

  type t =
     | A of { x : int; y: string }
     | ...

The argument of the constructor is a full-fledged record type. All features of records are available: dot notation, mutable fields, polymorphic fields, punning syntax, record override. You can write:

Static exceptions

In this post, I propose Static Exceptions as a new language feature allowing programmers to express interesting control flows in a compact way.

A note about the performance of Printf and Format

The goal is to display the following to stdout:


How would you implement that in OCaml? For such a simple task, we probably expect the program to be IO bound, right? Ok, let's try with the idiomatic way, which is to use format strings as provided by the Printf module from OCaml standard library:

Type-based selection of label and constructors

Most languages provide some way to manipulate tuples of values with a proper label for each field. They are called structures in C, records in OCaml; objects as found in most mainstream OO languages extend this same notion.

ML workshop 2012: call for participation

Registration is now open for ICFP and affiliated events, including the ML workshop 2012. Researchers, developers and users of OCaml and other languages of the ML family (SML, F#) are invited to participate to the workshop, on September 13. This is between the main ICFP conference and the OCaml Users and Developers Workshop, also of interest for the OCaml community.

Syntax extensions without Camlp4: let's do it!

In a previous post, I've described a proposal on how to get rid of Camlp4 to write simple syntax extensions. This proposal slowly becomes a reality:

ML workshop 2012: call for presentations!

I'm pleased to announce that the next instance of the ML workshop will take place on September 13th in Copenhagen.

ML2012 will be an informal workshop targeting both researchers, implementors, and users of ML languages (like Standard ML, OCaml, and F#).

Runtime Types

It is often useful to get access to types at runtime, in order to implement generic type-driven operations. A typical example is a generic value pretty-printer. Unfortunately, the OCaml compiler does not keep type information at runtime. At LexiFi, we have extended OCaml to support runtime types.

Syntax extensions without Camlp4

In this post, I'd like to propose a new approach to extending the syntax of OCaml that does not depend on Camlp4. This proposal is the result of discussions with Xavier Clerc, Fabrice Le Fessant, Maxence Guesdon, and has been presented to the latest meeting of the Caml Consortium. It was also quickly mentioned by Xavier Leroy during his talk at the latest OCaml Users Meeting.

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