This is the default Logtalk documenting tool for generating API documentation for libraries and applications. It uses the structural reflection API to extract and output in XML format relevant documentation about a source file, a library or directory of source files, or all loaded source files. The tool predicates accept several options for generating the XML files, including the output directory.

The lgtdoc/xml directory contains several ready to use Bash and PowerShell scripts for converting the XML documenting files into final formats including (X)HTML, PDF, Markdown, and reStructuredText (for use with Sphinx), or plain text files. The scripts are described in their man pages and made available in the system path by default. See also the lgtdoc/xml/NOTES.md for details, including the required third-party software.

API documentation

This tool API documentation is available at:



This tool can be loaded using the query:

| ?- logtalk_load(lgtdoc(loader)).


To test this tool, load the tester.lgt file:

| ?- logtalk_load(lgtdoc(tester)).

Documenting source code

For information on documenting your source code, notably on documenting directives, consult the documenting section of the User Manual:


Extracting documenting information from your source code using with this tool requires compiling the source files using the source_data(on) compiler flag. For example:

| ?- logtalk_load(source_file, [source_data(on)]).

Usually, this flag is set for all application source files in the corresponding loader file. In alternative, you may also turn on the source_data flag globally by typing:

| ?- set_logtalk_flag(source_data, on).

The tool API allows generating documentation for libraries, directories, and files, complemented with library, directory, entity, and predicate indexes. Note that the source files to be documented must be loaded prior to using this tool predicates to generate the documentation.

Generating documentation

For a simple application, assuming a library alias is defined for it (e.g. my_app), and at the top-level interpreter, we can generate the application documentation by typing:

| ?- {my_app(loader)}.

| ?- {lgtdoc(loader)}.

| ?- lgtdoc::library(my_app).

By default, the documenting XML files are created in a xml_docs directory in the current working directory. But usually all documenting files are collected for both the application and the libraries it uses in a common directory so that all documentation links resolved properly. The lgtdoc predicates can take a list of options to customize the generated XML documenting files. See the remarks section in the lgtdocp protocol documentation for details on the available options.

After generating the XML documenting files, these can be easily converted into final formats using the provided scripts. For example, assuming that we want to generate HTML documentation:

$ cd xml_docs
$ lgt2html -t "My app"

To generate the documentation in Sphinx format instead (as used by Logtalk itself for its APIs):

$ cd xml_docs
$ lgt2rst -s -- -q -p "Application name" -a "Author name" -v "Version X.YZ.P"
$ make html

In this case, the generated documentation will be in the xml_docs/_build/html/ directory. See the scripts man pages or call them using the -h option to learn more about their supported options.

For more complex applications, you can use the doclet tool to define a doclet to automate all the steps required to generate documentation. The doclet message that triggers the process can also be sent automatically when the make tool is used with the documentation target.

Documentation linter checks

When the lgtdoc_missing_directives flag is set to warning (its usual default value), the lgtdoc tool prints warnings on missing entity info/1 directives and missing predicate info/2 and mode/2 directives.

When the lgtdoc_missing_info_key flag is set to warning (its usual default value), the lgtdoc tool prints warnings on entity info/1 directive and predicate info/2 directive missing de facto required keys (e.g comment, parameters or parnames for parametric entities, arguments or argnames for predicates/non-terminals with arguments).

When the lgtdoc_invalid_dates flag is set to warning (its usual default value), the lgtdoc tool prints warnings on invalid dates (including dates in the future) in info/1 directives.

When the lgtdoc_non_standard_exceptions flag is set to warning (its usual default value), the lgtdoc tool prints warnings on non-standard exceptions. This linter check is particularly effective in detecting typos when specifying standard exceptions.

When the lgtdoc_missing_punctuation flag is set to warning (its usual default value), the lgtdoc tool prints warnings on missing ending periods (full stops), exclamation marks, or question marks in info/1-2 directives (in comments, remarks, parameter descriptions, and argument descriptions).

Set a flag value to silent to turn off the corresponding linter warnings.