Contribute to ocaml/camlp4 development by creating an account on GitHub. #toc Camlp4 is part of the standard OCaml distribution and Camlp5 is distributed separately. name change. Camlp5 Reference Manual (by Daniel de Rauglaudre). Camlp4 stands for Caml Preprocessor and Pretty-Printer and one of its most important applications is the definition of domain-specific.

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I know this sounds confusing, as messing with quotations can often be, but in most cases it is easier to learn them by example. With quotations this is easier. If, instead, you simply quote the line of code above, CamlP4 will expand the quotation into the same AST.

CamlP4 gives OCaml programmers much of the power of metaprogramming available in Lisp languages, added with static type checking and customizable components.


He also uses quotations in original syntax in the earlier parts, rendering the example code unusable in current versions of OCaml in some cases he linked to newer versions that work. To learn CamlP4, you must learn this alt syntax. This CamlP5 tutorial by Martin Acmlp4 is very good.

For example, this piece of code:.

Camlp4 – Wikipedia

A syntax extension csmlp4 defined by a compiled OCaml module, which is passed to the camlp4o executable along with the program to process. Most of them are linked in a previous part. The relevant files are pointed later, in the section about parsers. The output of the program is as follows, showing that the fac function factorial only computes products that were not computed previously:.

Quotations allow the programmer to treat a piece of code as data instead of being part of the program itself. The following example defines a syntax extension of Mnual. This post is meant to be a guide to the available documentation and tutorials about CamlP4, assuming no previous experience with it. It is also possible to define new printers, though most of the time this is not very useful.


The only thing to be aware of is that OCaml code inside quotations must use the revised syntax. Grammars and Extensible Parsers CamlP4 makes it easy to create parsers, because it includes an embedded mabual for parser generation.

camlo4 The CamlP4 wiki has a page on quotationsand a page making an analogy between quotations and strings. CamlP4 itself is written in mznual syntax.

Sources and Final Thoughts CamlP4 gives OCaml programmers much of the power of metaprogramming available in Lisp languages, added with static type checking and customizable components.

De Rauglaudre maintains a separate backward-compatible version, which has been renamed Camlp5. Jake Donham probably knows a lot more about this stuff than me, but sometimes he seems to be writing to people who already know about CamlP4, especially in the first few posts.

Manuaal is mostly used as a metaprogramming tool for OCaml, but it can be used in many ways: The notion of concrete syntax refers to the format in which the abstract syntax is represented. It can be output in a binary form, e. It is often used to write syntax extensions to OCaml, like adding support for a notation for monads or for list comprehensions.

A (meta-)guide to CamlP4: Metaprogramming in OCaml ยท Andrei Formiga

However, it is a quite complex piece of software and this is sometimes exposed to users. The abstract syntax tree is at the center of the syntax extensions, which are in fact OCaml programs.


This is basic in code generation: Several libraries are provided which facilitate the specific manipulation of OCaml syntax trees. The only thing that the developer has to do is write a Camlp4 grammar which converts the domain-specific language in question into a regular OCaml program. Besides that, there are always the sources. All of the examples below are for Camlp5 or the previous version of Camlp4 versions 3.

Its original author is Daniel de Rauglaudre. If you know the revised syntax, you can start to use quotations to generate OCaml code.

A (meta-)guide to CamlP4: Metaprogramming in OCaml

I just found out about it as I was almost finished writing this post. From the point of view of syntax extensions for OCaml, CamlP4 parses OCaml code, most likely using an extended syntax, generates an AST that may be filtered, and then prints it. They are widely used in Lisp because of its uniform representation for code and data, and are widely used when programming in CamlP4 because they make it easier to generate code.

It provides a set of OCaml libraries that are cajlp4 to define grammars as well as loadable syntax extensions of such grammars. So CamlP4 parses its input and then builds an abstract syntax tree out of it. The sequence could start better. CamlP4 makes it easy to create parsers, because it includes an embedded notation for parser generation.