Galabar Camlp4 underwent a major revision between the version included in ocaml 3. So the first order of business if you want to learn to use CamlP4 is learning the Revised syntax. Given textual input, CamlP4 parses the input into an abstract syntax tree, which is then printed in some format. Camlp4 includes a domain-specific language as it provides syntax extensions which ease the development of syntax extensions. Grammars and Extensible Parsers CamlP4 makes it easy to create parsers, because it includes an embedded notation for parser generation. Some things CamlP4 can do, like integration of external syntaxes in OCaml programs, are not easy to replicate in Lisp.
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Given textual input, CamlP4 parses the input into an abstract syntax tree, which is then printed in some format. From Wikipedia, the free ttuorial. Since OCaml is a multi-paradigm language, with an interactive toplevel and a native code compiler, it can be used as a backend for camop4 kind of original language.
The CamlP4 wiki has a page on quotationsand a page making an analogy between quotations and strings. Other target languages can also be used, such as C. The only thing to be aware of is that OCaml code inside quotations must use the revised syntax. The new CamlP4 wiki has useful stuff, although it is incomplete both as a tutorial and as a reference. To learn CamlP4, you must learn this alt syntax.
Grammars and Extensible Parsers CamlP4 makes it easy to create parsers, because it includes an embedded notation for parser generation. Jake Donham has written a series of posts in his blog about CamlP4. OCaml tutorials 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.
Quotations allow the programmer to treat a piece of code as data instead of being part of the program itself. Richard Jones posted an example in the official Caml-list for wrapping pattern matching in a predicate. Actually, although the old CamlP4 had an official reference manual and tutorial, the new CamlP4 has neither.
I hope this post helps people get up to speed in tutlrial this handy tool. The camlp4 commands Instead, each template has gaps that must be filled with data which depends on the situation.
Views Read Edit View history. CamlP4 is mostly used as a metaprogramming tool for OCaml, but it can be used in many ways: The output of the program is as follows, showing that the fac function factorial only computes products that were not computed previously:.
Several libraries are provided which facilitate the specific manipulation of OCaml syntax trees. Between parsing and printing, it is possible to define Cqmlp4 Filters that can transform the tree, including maps and folds over tutoriql. So the first order of business if you want to learn to use CamlP4 is learning the Revised syntax. You could feed the output of the pretty-printer to the OCaml compiler, thus effectively activating the syntax extension.
This page in the CamlP4 wiki has a good overview about using CamlP4 by itself and together with a compiler. As I mentioned, this is not a tutorial on CamlP4. Or read the CamlP4 sources, in this case the OCaml parsers. The difference is only at the level of the concrete syntax, since these three versions are equivalent representations of the same abstract syntax tree.
It is not necessary to use a. Support for the original syntax inside quotations was added in OCaml 3. Back to the Revised syntax: The abstract syntax tree is at the center of the syntax extensions, which are in fact OCaml programs.
Warning this page contains advanced material. Although the definition of grammars must be tutoriaal 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.
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. 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.
As with most things in CamlP4, quotations are also customizable. The relevant files are pointed later, in the section about parsers.
The following example defines a syntax extension of OCaml. 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.
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.
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. 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. 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.
Foreach Tutorial (Camlp4 3.10)
What is it about? We are talking about truly modifying the syntax of OCaml. Yes, in theory anyone could modify the syntax of this programming language, without rewriting a whole dedicated parser. Camlp5 is the tool that lets you do this. And many syntax enhancements can be performed in relatively few lines of code.
Kasida Between parsing and printing, it is possible to define AST Filters that can transform the tree, including maps and folds over it. This page was last edited on 18 Novemberat They are tutlrial used in Lisp because of its uniform representation for code and data, and are widely used when programming in CamlP4 because they make it caml;4 to generate code. CamlP4 comes with parsers for the syntax of OCaml revised and original variants, possibly others. Ambassador to the Computers: Reading Camlp4 Conceptually, the plan is simple: This page in the CamlP4 wiki has a good overview about using CamlP4 by itself and together with a compiler. Quotations also allow for antiquotations, which are parts of a quotation that should be evaluated instead of directly transformed to AST nodes. CamlP4 is generally used to generate OCaml code, one way or another. And now for the punchline: If you know the revised syntax, you can start to use quotations to generate OCaml code.
CAMLP4 TUTORIAL PDF
For example, this piece of code:. Jake Donham has written a series of posts in his blog about CamlP4. Support for the original syntax inside quotations was added in OCaml 3. The difference is only at the level of the concrete syntax, since these three versions tutorkal equivalent representations of the same abstract syntax tree. If, instead, you simply quote the line of code above, Tutodial will expand the quotation into the same AST. This is similar to the way format strings work in printf-like functions.