Camlp4 Deprecation Warning: this tutorial describes technology that is considered obsolete. It’s been replaced by extensions points and ppx rewriters. Camlp4 is part of the standard OCaml distribution and Camlp5 is distributed The title of the tutorial says Camlp4 but that is because it was written prior to the. Many of the tutorials below need updating and tutorials on many new topics are Camlp4 Tutorial (by Jake Donham), to build syntax extensions for OCaml with.

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Before attempting to learn CamlP4, it is recommended to learn how to program cmlp4 OCaml reasonably well, and to have at least some familiarity with parsing and programming language tools.

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

A syntax extension is defined by a compiled OCaml module, which is passed to the camlp4o executable along with the program to process. A Camlp4 preprocessor operates by loading a collection of compiled modules which define a parser as well as a pretty-printer: If, instead, you simply quote the line of code above, CamlP4 will expand campl4 quotation into the same AST.

In the beta announcement, there was mention of new binaries camlp4xxx that come preloaded with selections of new and old syntaxes. Memoization consists in storing the results of previous computations in a table so that the actual computation of the function for each possible argument occurs at most once. To learn how to use quotations to generate OCaml AST nodes, you can look at this appendix from the same manual.


Ambassador to the Computers: Reading Camlp4

However, this has some disadvanges: The following example defines a syntax extension of OCaml. The section about the Revised syntax in the latest official reference manual for the old CamlP4 version 3.

This CamlP5 tutorial by Martin Jambon is very good. As this list shows, it is a very powerful and useful tool for parsing and metaprogramming.

Although the definition of grammars must be done in OCaml, the parser that is tutorixl 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. Instead, each template has gaps that tutoriall be filled with data which depends on the situation. CamlP4 uses an alternative concrete syntax for OCaml.

The wiki has a page with a simple extension for float expressions this extension uses a map over the AST to avoid having to rewrite many grammar productions. Any turorial 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.

Camlp4 underwent a major revision between the version included in ocaml 3. CamlP4 has an embedded notation for parser generation.

Camlp4 – Wikipedia

Retrieved from ” https: 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.


For now, there are no better options, so the only way out is to read both sources and try to integrate them mentally.

They are widely used in Tutrial 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. Tutofial output of the program is as follows, showing that the fac function factorial only computes products that were not computed previously:.

OCaml tutorials

Grammars and Extensible Parsers: It provides a new keywordmemowhich can be used as a replacement for function and provides automatic memoization of functions with pattern matching. From Wikipedia, the free encyclopedia. External Documents The semi-official documentation: Some things CamlP4 can do, like integration of external syntaxes in OCaml programs, are not easy to replicate in Lisp.

Besides that, there are always the sources. Conceptually, the plan is simple: The CamlP4 wiki has a page on quotations camlp44, and a page making an analogy between quotations and strings.

The series of posts on CamlP4 over at Ambassador at the Computers is a good source, with some caveats. Domain-specific languages are a major application of Camlp4. Quotations and Abstract Syntax Quotations allow the programmer to treat a piece of code as data instead of being part of the program itself.