This chapter describes OCamldoc, a tool that generates documentation from special comments embedded in source files. The comments used by OCamldoc are of the form (**…*) and follow the format described in section 15.2.
OCamldoc can produce documentation in various formats: HTML, LATEX, TeXinfo, Unix man pages, and dot dependency graphs. Moreover, users can add their own custom generators, as explained in section 15.3.
In this chapter, we use the word element to refer to any of the following parts of an OCaml source file: a type declaration, a value, a module, an exception, a module type, a type constructor, a record field, a class, a class type, a class method, a class value or a class inheritance clause.
OCamldoc is invoked via the command ocamldoc, as follows:
ocamldoc options sourcefiles
The following options determine the format for the generated documentation.
OCamldoc calls the OCaml type-checker to obtain type information. The following options impact the type-checking phase. They have the same meaning as for the ocamlc and ocamlopt commands.
The following options apply in conjunction with the -html option:
The following options apply in conjunction with the -latex option:
These options are useful when you have, for example, a type and a value with the same name. If you do not specify prefixes, LATEX will complain about multiply defined labels.
The following options apply in conjunction with the -texi option:
The following options apply in conjunction with the -dot option:
The following options apply in conjunction with the -man option:
Information on a module can be extracted either from the .mli or .ml file, or both, depending on the files given on the command line. When both .mli and .ml files are given for the same module, information extracted from these files is merged according to the following rules:
The following rules must be respected in order to avoid name clashes resulting in cross-reference errors:
open Foo (* which has a module Bar with a value x *)
module Foo =
struct
module Bar =
struct
let x = 1
end
end
let dummy = Bar.x
In this case, OCamldoc will associate Bar.x to the x of module
Foo defined just above, instead of to the Bar.x defined in the
opened module Foo.
Comments containing documentation material are called special comments and are written between (** and *). Special comments must start exactly with (**. Comments beginning with ( and more than two * are ignored.
OCamldoc can associate comments to some elements of the language encountered in the source files. The association is made according to the locations of comments with respect to the language elements. The locations of comments in .mli and .ml files are different.
A special comment is associated to an element if it is placed before or
after the element.
A special comment before an element is associated to this element if :
A special comment after an element is associated to this element if there is no blank line or comment between the special comment and the element.
There are two exceptions: for type constructors and record fields in type definitions, the associated comment can only be placed after the constructor or field definition, without blank lines or other comments between them. The special comment for a type constructor with another type constructor following must be placed before the ’|’ character separating the two constructors.
The following sample interface file foo.mli illustrates the placement rules for comments in .mli files.
(** The first special comment of the file is the comment associated
with the whole module.*)
(** Special comments can be placed between elements and are kept
by the OCamldoc tool, but are not associated to any element.
@-tags in these comments are ignored.*)
(*******************************************************************)
(** Comments like the one above, with more than two asterisks,
are ignored. *)
(** The comment for function f. *)
val f : int -> int -> int
(** The continuation of the comment for function f. *)
(** Comment for exception My_exception, even with a simple comment
between the special comment and the exception.*)
(* Hello, I'm a simple comment :-) *)
exception My_exception of (int -> int) * int
(** Comment for type weather *)
type weather =
| Rain of int (** The comment for construtor Rain *)
| Sun (** The comment for constructor Sun *)
(** Comment for type weather2 *)
type weather2 =
| Rain of int (** The comment for construtor Rain *)
| Sun (** The comment for constructor Sun *)
(** I can continue the comment for type weather2 here
because there is already a comment associated to the last constructor.*)
(** The comment for type my_record *)
type my_record = {
val foo : int ; (** Comment for field foo *)
val bar : string ; (** Comment for field bar *)
}
(** Continuation of comment for type my_record *)
(** Comment for foo *)
val foo : string
(** This comment is associated to foo and not to bar. *)
val bar : string
(** This comment is assciated to bar. *)
(** The comment for class my_class *)
class my_class :
object
(** A comment to describe inheritance from cl *)
inherit cl
(** The comment for attribute tutu *)
val mutable tutu : string
(** The comment for attribute toto. *)
val toto : int
(** This comment is not attached to titi since
there is a blank line before titi, but is kept
as a comment in the class. *)
val titi : string
(** Comment for method toto *)
method toto : string
(** Comment for method m *)
method m : float -> int
end
(** The comment for the class type my_class_type *)
class type my_class_type =
object
(** The comment for variable x. *)
val mutable x : int
(** The commend for method m. *)
method m : int -> int
end
(** The comment for module Foo *)
module Foo =
struct
(** The comment for x *)
val x : int
(** A special comment that is kept but not associated to any element *)
end
(** The comment for module type my_module_type. *)
module type my_module_type =
sig
(** The comment for value x. *)
val x : int
(** The comment for module M. *)
module M =
struct
(** The comment for value y. *)
val y : int
(* ... *)
end
end
A special comment is associated to an element if it is placed before the element and there is no blank line between the comment and the element. Meanwhile, there can be a simple comment between the special comment and the element. There are two exceptions, for type constructors and record fields in type definitions, whose associated comment must be placed after the constructor or field definition, without blank line between them. The special comment for a type constructor with another type constructor following must be placed before the ’|’ character separating the two constructors.
The following example of file toto.ml shows where to place comments in a .ml file.
(** The first special comment of the file is the comment associated
to the whole module.*)
(** The comment for function f *)
let f x y = x + y
(** This comment is not attached to any element since there is another
special comment just before the next element. *)
(** Comment for exception My_exception, even with a simple comment
between the special comment and the exception.*)
(* A simple comment. *)
exception My_exception of (int -> int) * int
(** Comment for type weather *)
type weather =
| Rain of int (** The comment for constructor Rain *)
| Sun (** The comment for constructor Sun *)
(** The comment for type my_record *)
type my_record = {
val foo : int ; (** Comment for field foo *)
val bar : string ; (** Comment for field bar *)
}
(** The comment for class my_class *)
class my_class =
object
(** A comment to describe inheritance from cl *)
inherit cl
(** The comment for the instance variable tutu *)
val mutable tutu = "tutu"
(** The comment for toto *)
val toto = 1
val titi = "titi"
(** Comment for method toto *)
method toto = tutu ^ "!"
(** Comment for method m *)
method m (f : float) = 1
end
(** The comment for class type my_class_type *)
class type my_class_type =
object
(** The comment for the instance variable x. *)
val mutable x : int
(** The commend for method m. *)
method m : int -> int
end
(** The comment for module Foo *)
module Foo =
struct
(** The comment for x *)
val x : int
(** A special comment in the class, but not associated to any element. *)
end
(** The comment for module type my_module_type. *)
module type my_module_type =
sig
(* Comment for value x. *)
val x : int
(* ... *)
end
The special comment (**/**) tells OCamldoc to discard elements placed after this comment, up to the end of the current class, class type, module or module type, or up to the next stop comment. For instance:
class type foo =
object
(** comment for method m *)
method m : string
(**/**)
(** This method won't appear in the documentation *)
method bar : int
end
(** This value appears in the documentation, since the Stop special comment
in the class does not affect the parent module of the class.*)
val foo : string
(**/**)
(** The value bar does not appear in the documentation.*)
val bar : string
(**/**)
(** The type t appears since in the documentation since the previous stop comment
toggled off the "no documentation mode". *)
type t = string
The -no-stop option to ocamldoc causes the Stop special comments to be ignored.
The inside of documentation comments (**…*) consists of free-form text with optional formatting annotations, followed by optional tags giving more specific information about parameters, version, authors, … The tags are distinguished by a leading @ character. Thus, a documentation comment has the following shape:
(** The comment begins with a description, which is text formatted according to the rules described in the next section. The description continues until the first non-escaped '@' character. @author Mr Smith @param x description for parameter x *)
Some elements support only a subset of all @-tags. Tags that are not relevant to the documented element are simply ignored. For instance, all tags are ignored when documenting type constructors, record fields, and class inheritance clauses. Similarly, a @param tag on a class instance variable is ignored.
At last, (**) is the empty documentation comment.
Here is the BNF grammar for the simple markup language used to format text descriptions.
text ::= (text_element)+
text_element ::=
| | {[0-9]+ text} | format text as a section header; the integer following { indicates the sectioning level. |
| | {[0-9]+:label text} | same, but also associate the name label to the current point. This point can be referenced by its fully-qualified label in a {! command, just like any other element. |
| | {b text} | set text in bold. |
| | {i text} | set text in italic. |
| | {e text} | emphasize text. |
| | {C text} | center text. |
| | {L text} | left align text. |
| | {R text} | right align text. |
| | {ul list} | build a list. |
| | {ol list} | build an enumerated list. |
| | {{:string}text} | put a link to the given address (given as a string) on the given text. |
| | [string] | set the given string in source code style. |
| | {[string]} | set the given string in preformatted source code style. |
| | {v string v} | set the given string in verbatim style. |
| | {% string %} | take the given string as raw LATEX code. |
| | {!string} | insert a reference to the element named string. string must be a fully qualified element name, for example Foo.Bar.t. The kind of the referenced element can be forced (useful when various elements have the same qualified name) with the following syntax: {!kind: Foo.Bar.t} where kind can be module, modtype, class, classtype, val, type, exception, attribute, method or section. |
| | {!modules: string string ...} | insert an index table for the given module names. Used in HTML only. |
| | {!indexlist} | insert a table of links to the various indexes (types, values, modules, ...). Used in HTML only. |
| | {^ text} | set text in superscript. |
| | {_ text} | set text in subscript. |
| | escaped_string | typeset the given string as is; special characters (’{’, ’}’, ’[’, ’]’ and ’@’) must be escaped by a ’\’ |
| | blank_line | force a new line. |
list ::=
| ({- text})+
| ({li text})+
A shortcut syntax exists for lists and enumerated lists:
(** Here is a {b list}
- item 1
- item 2
- item 3
The list is ended by the blank line.*)
is equivalent to:
(** Here is a {b list}
{ul {- item 1}
{- item 2}
{- item 3}}
The list is ended by the blank line.*)
The same shortcut is available for enumerated lists, using ’+’ instead of ’-’. Note that only one list can be defined by this shortcut in nested lists.
In the description of a value, type, exception, module, module type, class or class type, the first sentence is sometimes used in indexes, or when just a part of the description is needed. The first sentence is composed of the first characters of the description, until
outside of the following text formatting : {ul list}, {ol list}, [string], {[string]}, {v string v}, {% string%}, {!string}, {^ text}, {_ text}.
The folowing table gives the list of predefined @-tags, with their
syntax and meaning.
| @author string | The author of the element. One author by @author tag. There may be several @author tags for the same element. |
| @deprecated text | The text should describe when the element was deprecated, what to use as a replacement, and possibly the reason for deprecation. |
| @param id text | Associate the given description (text) to the given parameter name id. This tag is used for functions, methods, classes and functors. |
| @raise Exc text | Explain that the element may raise the exception Exc. |
| @return text | Describe the return value and its possible values. This tag is used for functions and methods. |
| @see <url> text | Add a reference to the URL between ’<’ and ’>’ with the given text as comment. |
| @see ’filename’ text | Add a reference to the given file name (written between single quotes), with the given text as comment. |
| @see "document name" text | Add a reference to the given document name (written between double quotes), with the given text as comment. |
| @since string | Indicate when the element was introduced. |
| @before v text | Associate the given description (text) to the given version v in order to document compatibility issues. |
| @version string | The version number for the element. |
You can use custom tags in the documentation comments, but they will have no effect if the generator used does not handle them. To use a custom tag, for example foo, just put @foo with some text in your comment, as in:
(** My comment to show you a custom tag. @foo this is the text argument to the [foo] custom tag. *)
To handle custom tags, you need to define a custom generator, as explained in section 15.3.2.
OCamldoc operates in two steps:
Users can provide their own documentation generator to be used during step 2 instead of the default generators. All the information retrieved during the analysis step is available through the Odoc_info module, which gives access to all the types and functions representing the elements found in the given modules, with their associated description.
The files you can used to define custom generators are installed in the ocamldoc sub-directory of the OCaml standard library.
A generator class is a class of type Odoc_args.doc_generator.
It has only one method
generator : Odoc_info.Module.t_module list -> unit
This method will be called with the list of analysed and possibly
merged Odoc_info.t_module structures.
Of course the class can have other methods, but the object of this
class must be coerced to Odoc_args.doc_generator before being
passed to the function
Odoc_args.set_doc_generator : Odoc_args.doc_generator -> unit
which installs the new documentation generator.
The following example shows how to define and install a new documentation generator. See the odoc_fhtml generator (in the Ocamldoc Hump) for a complete example.
class my_doc_gen =
object
(* ... *)
method generate module_list =
(* ... *)
()
(* ... *)
end
let my_generator = new my_doc_gen
let _ = Odoc_args.set_doc_generator (my_generator :> Odoc_args.doc_generator)
Note: The new class can inherit from Odoc_html.html, Odoc_latex.latex, Odoc_man.man, Odoc_texi.texi or Odoc_dot.dot, and redefine only some methods to benefit from the existing methods.
Making a custom generator handle custom tags (see 15.2.5) is very simple.
Here is how to develop a HTML generator handling your custom tags.
The class Odoc_html.html inherits from the class Odoc_html.info, containing a field tag_functions which is a list pairs composed of a custom tag (e.g. ’foo’) and a function taking a text and returning HTML code (of type string). To handle a new tag bar, create a HTML generator class from the existing one and complete the tag_functions field:
class my_gen =
object(self)
inherit Odoc_html.html
(** Return HTML code for the given text of a bar tag. *)
method html_of_bar t = (* your code here *)
initializer
tag_functions <- ("bar", self#html_of_bar) :: tag_functions
end
Another method of the class Odoc_html.info will look for the function associated to a custom tag and apply it to the text given to the tag. If no function is associated to a custom tag, then the method prints a warning message on stderr.
As for the HTML custom generator, you can define a new LATEX(resp. man) generator by inheriting from the class Odoc_latex.latex (resp. Odoc_man.man) and adding your own tag handler to the field tag_functions.
The command line analysis is performed after loading the module containing the
documentation generator, thus allowing command line options to be added to the
list of existing ones. Adding an option can be done with the function
Odoc_args.add_option : string * Arg.spec * string -> unit
Note: Existing command line options can be redefined using this function.
Let custom.ml be the file defining a new generator class.
Compilation of custom.ml can be performed by the following command :
ocamlc -I +ocamldoc -c custom.ml
The file custom.cmo is created and can be used this way :
ocamldoc -g custom.cmo other-options source-files
It is important not to give the -html or any other option selecting a
built in generator to ocamldoc,
which would result in using this generator instead of the one you just loaded.
It is possible to define a generator class in several modules, which
are defined in several files file1.ml[i], file2.ml[i], ...,
fileN.ml[i]. A .cma library file must
be created, including all these files.
The following commands create the custom.cma file from files file1.ml[i], ...,
fileN.ml[i] :
ocamlc -I +ocamldoc -c file1.ml[i]
ocamlc -I +ocamldoc -c file2.ml[i]
...
ocamlc -I +ocamldoc -c fileN.ml[i]
ocamlc -o custom.cma -a file1.cmo file2.cmo ... fileN.cmo
Then, the following command uses custom.cma as custom generator:
ocamldoc -g custom.cma other-options source-files
Again, it is important not to give the -html or any other option selecting a
built in generator to ocamldoc,
which would result in using this generator instead of the one you just loaded.