# C++ API of the Documentation classes¶

This section includes information for using the pure C++ API for the documentation classes, which can be accessed after including:

# include <bob.extension/documentation.h>


The classes, which are described in more detail below, can be used to format the documentation of your C/C++ functions that are bound to Python. Any free text that you specify to describe your functions will be interpreted as reStructuredText. Hence, it is possible to use any directives like .. note::, .. math::, and even links inside the documentation like :py:class: and references as [REF]_.

## Function Documentation¶

class bob::extension::FunctionDoc

To document a function (either a stand-alone function or a member function of a class), you should use the bob::extension::FunctionDoc().

bob::extension::FunctionDoc(const char *const function_name, const char *const short_desctiption, const char *const long_description = NULL, bool is_member_function = false)

In the constructor, you specify the function name and a short description. If wanted, you can define a longer description as well. When you use this FunctionDoc to document a member function of a class, please set is_member_function = true.

FunctionDoc clone(const char *const function_name)

Returns a copy of this documentation class, where the function name is replaced by the given one. This is useful, when a function is bound with several names.

FunctionDoc &add_prototype(const char *const variables, const char *const return_value = "None")

Adds a prototype of the documented function declaration to the function. All variables and all return_value’s listed must be documented using the add_parameter() or add_return() functions. Only the default return value None does not need documentation.

variables is a single string containing a comma-separated list of parameter names. Use ..., [name] to indicate that name is name is an optional parameter.

return_value is a single string containing a comma-separated list of return value names. If a single name is given, only a single value is returned, otherwise a tuple will be returned by your function.

Note

Each FunctionDoc needs at least one prototype. In opposition to pure Python functions, specifying multiple prototypes is allowed here as well.

FunctionDoc &add_parameter(const char *const parameter_name, const char *const parameter_type, const char *const parameter_description)

Adds a description for a given parameter.

parameter_name must be one of the names listed in the variables of the add_prototype() function.

parameter_type specifies the expected type of this parameter. You can use any free text to describe the type. When :py:class: directives or similar are used, they will be interpreted correctly.

parameter_description includes free text to describe, what the parameter is used for.

FunctionDoc &add_return(const char *const return_name, const char *const return_type, const char *const return_description)

Adds a description for a given return value.

return_name must be one of the names listed as a return_value of the add_prototype() function.

return_type specifies the type of this return value. You can use any free text to describe the type. When :py:class: directives or similar are used, they will be interpreted correctly.

return_description includes free text to describe, what the return value contains.

const char *const name() const

Returns the name of the function defined in the constructor.

const char *const doc(const unsigned alignment = 72, const unsigned indent = 0) const

Generates and returns the documentation string. The free text in the documentation is aligned to alignment characters, by default 72, so that it can be viewed correctly inside of an 80-character Python console. The indent is an internal parameter and should not be changed.

char **kwlist(unsigned index) const

Returns the list of keyword arguments for the given prototype index added with the add_prototype() function. This list is in the desired format to be passed as the keywords parameter to the PyArg_ParseTupleAndKeywords() function during your bindings.

void print_usage() const

Prints a function usage string to console, including all information specified by the member functions above.

All functions adding information to the bob::extension::FunctionDoc return a reference to the current object, so that you can use it inline, like:

auto function_doc = bob::extension::FunctionDoc(
"function_name",
"Short description of the function",
"Long description of the function using reStructuredText including directives like :py:class:bob.blitz.array."
)
.add_parameter("param1", "int", "An int value used for ...")
.add_parameter("param2", "float", "[Default: 0.5] A float value describing ...")
.add_return("ret", ":py:class:bob.blitz.array", "An array ...")
;


During the binding of your function, you can use it, like:

static PyMethodDef module_methods[] = {
...
{
function_doc.name(),
(PyCFunction)function,
METH_VARARGS|METH_KEYWORDS,
function_doc.doc()
},
...
};


## Variables Documentation¶

class bob::extension::VariableDoc

To document a variable (either a stand-alone function or a member function of a class), you should use the bob::extension::VariableDoc().

bob::extension::VariableDoc(const char *const variable_name, const char *const variable_type, const char *const short_desctiption, const char *const long_description = NULL)

In the constructor, you specify the variable name, its type and a short description. The structure is identical to the FunctionDoc::add_parameter() function. If wanted, you can define a longer description as well.

char *name() const

Returns the name of the variable defined in the constructor.

char *doc(const unsigned alignment = 72) const

Generates and returns the documentation string, which is composed of the information provided in the constructor. The free text in the documentation is aligned to alignment characters, by default 72, so that it can be viewed correctly inside of an 80-character Python console.

## Class Documentation¶

class bob::extension::ClassDoc

To document a class including its constructor, you should use the bob::extension::ClassDoc().

bob::extension::ClassDoc(const char *const class_name, const char *const short_desctiption, const char *const long_description = NULL)

In the constructor, you specify the class name and a short description. If wanted, you can define a longer description as well.

ClassDoc &add_constructor(const FunctionDoc &constructor_doc)

Adds the documentation of the constructor, which itself is a FunctionDoc.

Note

You should specify the return value of your constructor to be "" to overwrite the default value "None".

Note

A class can have only a single constructor documentation. Hence, this function can be called only once for each class.

char *name() const

Returns the name of the class defined in the constructor.

char *doc(const unsigned alignment = 72) const

Generates and returns the documentation string, which is composed of the information provided in the constructor, and the constructor documentation. The free text in the documentation is aligned to alignment characters, by default 72, so that it can be viewed correctly inside of an 80-character Python console.

char **kwlist(unsigned index) const

Returns the list of keyword arguments of the constructor for the given prototype index added with the FunctionDoc::add_prototype() function. This list is in the desired format to be passed as the keywords parameter to the PyArg_ParseTupleAndKeywords() function during your bindings.

void print_usage() const

Prints the usage of the constructor. See FunctionDoc::print_usage() for details.

As for functions, the bob::extension::ClassDoc is designed to be used inline, like:

auto class_doc = bob::extension::ClassDoc(
"class_name",
"Short description of the class",
"Long description of the class using reStructuredText including directives like :py:class:bob.blitz.array."
)
.add_parameter("param2", "float", "[Default: 0.5] A float value describing ...")