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 following values:
- 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
PAGERor otherwise tries to find the
- A Callable term is interpreted as
program_name(Arg, ...). For example,
less('-r')would be the default. Note that the program name can be an absolute path if single quotes are used.
- help is det
- help(+What) is det
- Show help for What. What is a term that describes the
topics(s)to give help for. Notations for What are:
- This ambiguous form is most commonly used and shows all
matching documents. For example:
- Name / Arity
- Give help on predicates with matching Name/Arity. Arity may be unbound.
- Name // Arity
- 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
lessprogram. This behaviour is controlled by the Prolog flag
help_pager. See section level documentation.
- show_html_hook(+HTML:string) is semidet[multifile]
- Hook called to display the extracted HTML document. If this hook fails the HTML is rendered to the console as plain text using html_text/2.
- apropos(+Query) is det
- 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
non_terminal. For example:
?- apropos(c:close). ?- apropos(f:min).
- 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.
The following predicates are exported, but not or incorrectly documented.