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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This is similar to the way format strings work in printf-like functions. Views Read Edit View history. Several libraries are mahual which facilitate the specific manipulation of OCaml syntax trees. Many factors contribute to this. CamlP4 is mostly used as a metaprogramming tool for OCaml, but it can be used in many ways: CamlP4 is generally used to generate OCaml code, one way or another.
This page in the CamlP4 wiki has a good overview about using CamlP4 by itself and together with a compiler. So a fork ensued: The abstract syntax tree is at the center of the syntax extensions, which are in fact OCaml programs. 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.
It provides a set of OCaml libraries that are used to define grammars as well as loadable syntax extensions of such grammars. Putting it all together: It can be output in a binary form, e. It is also possible to have a quotation inside an antiquotation, and an antiquotation inside this quotation that is inside the antiquotation of the original quotation, and so on. 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.
To learn how to use quotations to generate OCaml AST nodes, you can look at this appendix from the same manual. However, this has some disadvanges: The CamlP4 wiki has a page on quotationsand a page making an analogy between quotations and strings.
This brings up another source of confusion: Actually, although the old CamlP4 had an official reference manual and tutorial, the new CamlP4 has neither.
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. It is or was completely compatible with the old versions of CamlP4, although apparently it is now introducing incompatible changes.
As I mentioned, this is not a tutorial on CamlP4. A Camlp4 preprocessor operates by loading a collection of compiled modules which define a parser as well as a pretty-printer: The series of posts on CamlP4 over at Ambassador at the Computers is a good source, with some caveats. As demonstrated by the definition of a revised syntax for OCaml, the same programming language can use different concrete syntaxes. 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.
Quotations allow the programmer to treat a piece of code as data instead of being part of the program itself. Quotations and Abstract Syntax Quotations allow the programmer to treat a piece of code as data instead of being part of the program itself.
The latter one is defined as an extension of the former, so you may need to consult both. Quotations also allow for antiquotations, which are parts of a quotation that should be evaluated instead of directly transformed to AST nodes. This is basic in code generation: Between parsing and printing, it is possible to define AST Filters that can transform the tree, including maps manuak folds over it.
Camlp4 – Wikipedia
You could feed the output of the pretty-printer to the OCaml compiler, thus effectively activating the syntax extension. Its original author is Daniel de Rauglaudre.
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. CamlP4 has an embedded notation for parser generation. If the target language is OCaml, simple syntax add-ons or syntactic sugar can be defined, in order to provide an expressivity which is not easy to achieve using the standard features of the OCaml language.
The Camlp4 syntax extension
Other target languages can also be used, such as C. As with most things in CamlP4, quotations are also customizable.
CamlP4 gives OCaml programmers much of the power of kanual available in Lisp languages, added with static type checking and customizable components. The sequence could start better. This tree can also be filtered before printing. Part 2 and part 3 are mnual quotations from the perspective of a user, while part 8 and part 9 are about implementing new quotations and antiquotations.
Since OCaml is a multi-paradigm language, with an interactive toplevel and a native code compiler, it can be used as a backend for any kind of original language. The relevant files are pointed later, in the section about parsers.
From Wikipedia, the free encyclopedia. The only thing that the developer maunal to do is write a Camlp4 grammar which converts the domain-specific language in question into a regular OCaml program.
The generated AST can be emitted by a pretty-printer, showing code in a readable format for humans. Or read the CamlP4 sources, in this case the OCaml parsers.
A proper tutorial would be quite useful, but it would also demand much more time from me, so I decided to do the next best thing: This page was last edited on 18 Novemberat 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. CamlP4 uses an alternative concrete syntax for OCaml. To use this from the OCaml compilers, you just need to use the -pp command-line flag.
The output of the program is as follows, showing that the fac function factorial only computes products that were not computed previously:.