This module provides help/1
and apropos/1 that
give help on a topic or searches the manual for relevant topics.
By default the result of help/1
is sent through a pager such as
less. This behaviour is controlled by the following:
- The Prolog flag help_pager, which can be set to one of the
- Never use a pager.
- Use default behaviour. This tries to determine whether Prolog is running
interactively in an environment that allows for a pager. If so it
examines the environment variable
PAGER or otherwise tries
to find the
- A Callable term is interpreted as
less('-r') would be the default. Note that the
program name can be an absolute path if single quotes are used.
- Show help for What. What is a term that describes
topics(s) to give help for. Notations for What
- This ambiguous form is most commonly used and shows all matching
documents. For example:
- Give help on predicates with matching Name/Arity. Arity
may be unbound.
- Give help on the matching DCG rule (non-terminal)
- Give help on the matching Prolog arithmetic functions.
- Give help on the matching C interface function
- Show the section from the manual with matching Label.
If an exact match fails this predicates attempts fuzzy matching and,
when successful, display the results headed by a warning that the
matches are based on fuzzy matching.
If possible, the results are sent through a pager such as the
less program. This behaviour is controlled by the Prolog
help_pager. See section level documentation.
- See also
- apropos/1 for
searching the manual names and summaries.
- Hook called to display the extracted HTML document. If this
hook fails the HTML is rendered to the console as plain text
- Print objects from the manual whose name or summary match with
Query. Query takes one of the following forms:
- Find objects matching Text and filter the results by Type.
Type matching is a case intensitive prefix match.
Defined types are
dcg and aliases
- Text is broken into tokens. A topic matches if all tokens
appear in the name or summary of the topic. Matching is case
insensitive. Results are ordered depending on the quality of the match.