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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It is also possible to have a quotation manjal an antiquotation, and an antiquotation acmlp4 this quotation that is inside the antiquotation of the original quotation, and so on. Besides that, there are always the sources. The output of the program is as follows, showing that the fac function factorial only computes products that were not computed previously:. This page in the CamlP4 wiki has a good overview about using CamlP4 by itself and together with a compiler.

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.

More examples can manuql found in the recommended sources below. However, this has some disadvanges:. Conceptually, the plan is simple: So CamlP4 parses its input and then builds an abstract syntax tree out of it.

If, instead, you simply quote the line of code above, CamlP4 will expand the quotation into the same AST.

However, this has some disadvanges: It is also possible to define new printers, though most of the time this is not very useful. However, it is a quite complex piece of software and this is sometimes exposed to users.


Actually, although the old CamlP4 had an official reference manual and tutorial, the new CamlP4 has neither. Furthering the difficulties, it is now fragmented CamlP4 and CamlP5 and not very well documented.

CamlP4 itself is written in this syntax. For example, this piece of code: Any loaded module can extend a grammar defined in another module, and an extension can not only add new productions, but also change existing ones or even delete them.


Retrieved from ” https: Its original author is Daniel de Rauglaudre. The following example defines a syntax extension of OCaml. Jake Donham probably knows a lot more about this stuff than me, but sometimes he seems to be writing to people who already famlp4 about CamlP4, especially in the first few posts. It provides a set of OCaml libraries that are used to define grammars as well as loadable syntax extensions of such grammars.

This page was last edited on 18 Novemberat CamlP4 uses an cammlp4 concrete syntax for OCaml. If you know the revised syntax, you can start to use quotations to generate OCaml code. So a fork ensued: This can be used for defining parsers or extending existing ones.

The reason for the title will be explained in a bit. Camlp4 stands for Caml Preprocessor and Pretty-Printer and one of its most important applications is the definition of domain-specific extensions of the syntax of OCaml.

Quotations and Abstract Syntax Quotations allow the programmer to treat a piece of code as data instead of being part of the program itself.

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

Although the definition of grammars must be done in OCaml, the parser that is being defined or extended is not necessarily related to OCaml, in which case the syntax tree that is being manipulated is not the one of OCaml.

OCaml syntax extensions Conceptually, the plan is simple: Before attempting to learn CamlP4, it is recommended to learn how to program in OCaml reasonably well, and to have at least some familiarity with parsing and programming language tools. Most of them are linked in a previous part.

CamlP4 is generally used to generate OCaml code, one way or another. The good thing about grammars and parsers in CamlP4 is that they are extensible.

The Camlp4 syntax extension

The relevant files are nanual later, in the section about parsers. This post is meant to be a guide to the available documentation and tutorials about CamlP4, assuming no previous experience with it. However, there is a good source of examples of the revised syntax: It is often used to write syntax extensions to OCaml, like adding support for a notation for monads or for list comprehensions.


As with most things in CamlP4, quotations are also customizable. The intention is to give the Big Picture, so that the details can be worked out later.

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

The section about the Revised syntax in the latest official reference manual for the old CamlP4 version manuall. CamlP4 has a printer that emits the AST in a binary, marshaled form for the OCaml compiler, which can then skip the parsing stages and use the tree directly.

However, this type is recursive as expected for an AST and trees for any non-trivial piece of code will be complicated to create as a value of the AST type.

Richard Jones posted an example in the official Caml-list for wrapping pattern matching in a predicate. The latter one is defined as an extension of the former, so you may need to consult both. The msnual AST can be emitted by a pretty-printer, showing code in a readable format for humans. As this list shows, it is a very powerful and useful tool for parsing and metaprogramming.

Views Read Edit View history. From Wikipedia, the free encyclopedia. They would all converge to an abstract syntax tree in a unique format that a compiler can handle. Back to the Revised syntax: To learn how to use quotations to generate OCaml AST nodes, you can look at this appendix from the same manual.