help
This tool provides basic on-line help for Logtalk features and libraries
when running in most operating-systems. For help on the Logtalk compiler
error and warning messages, see the tutor
tool.
API documentation
This tool API documentation is available at:
../../docs/library_index.html#help
For sample queries, please see the SCRIPT.txt
file in the tool
directory.
Loading
| ?- logtalk_load(help(loader)).
Testing
To test this tool, load the tester.lgt
file:
| ?- logtalk_load(help(tester)).
Supported operating-systems
Currently, support is limited to Linux, macOS, and Windows.
On Windows, the start
command must be available. On Linux, the
xdg-open
command must be available. On macOS, the command open
is used.
This tool relies on the library portable operating-system access abstraction.
Usage
After loading the tool, use the query help::help
to get started.
Experimental features
On POSIX systems, when using Ciao Prolog, ECLiPSe, GNU Prolog (1.5.1 or
later version), XVM, SICStus Prolog, SWI-Prolog, Trealla Prolog, or XSB
as the backend, apis/1
and handbook/0-1
predicates are made
available. These predicates open inline at the top-level interpreter the
Texinfo versions of the Handbook and the APIs documentation. The
optional argument is a starting node, which can be an atom, a predicate
indicator, or a non-terminal indicator. When there are several nodes for
the same argument (e.g. multiple implementations of the member/2
predicate), one of them will be displayed. Some examples:
| ?- help::handbook.
| ?- help::handbook(base64).
| ?- help::handbook(logtalk_load/2).
| ?- help::apis.
| ?- help::apis(check/2).
| ?- help::apis(message_tokens//2).
Although less useful, you can also browse the man
pages of Logtalk
scripts. For example:
| ?- help::man(logtalk_tester).
When you finish consult the documentation and quit the info
process,
you will be back to the top-level prompt (if you find that the top-level
have scrolled from its last position, try to set your terminal terminfo
to xterm-256colour
).
If you’re running Logtalk from a git clone of its repo, you will need to
run the scripts/update_html_docs.sh
or
scripts/update_html_docs.ps1
scripts to generate the APIs
documentation .info
file and also run the
manuals/sources/build_manuals.sh
or
manuals/sources/build_manuals.ps1
scripts to generated the Handbook
.info
file. In alternative, you can download the .info
files for
the latest stable release from the Logtalk website and save them to the
docs
and manuals
directories.
The required info
command is provided by the third-party texinfo
package (tested with version 6.8). On macOS, this package can be
installed with either MacPorts:
$ sudo port install texinfo
Or using Homebrew:
$ brew install texinfo
On Linux systems, use the distribution own package manager to install
the texinfo
package. For example, in Ubuntu systems:
$ sudo apt install info
Known issues
The open commands used to open documentation URLs drop the fragment part, thus preventing navigating to the specified position on the documentation page.
When browsing the Texinfo versions of the Handbook and the APIs documentation generated with a recent version of Sphinx and using a recent version of Texinfo, the Texinfo search feature often displays the previous nodes of the searched nodes.
ECLiPSe defines a help
prefix operator that forces wrapping this
atom between parenthesis when sending messages to the tool. E.g. use
(help)::help
instead of help::help
.