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This file is part of Logtalk https://logtalk.org/ SPDX-FileCopyrightText: 1998-2023 Paulo Moura <pmoura@logtalk.org> SPDX-License-Identifier: Apache-2.0

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

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](../../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), LVM, 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.

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`.