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
or otherwise tries to find the
- A Callable term is interpreted as
program_name(Arg, ...). For
less('-r') would be the default. Note that the
program name can be an absolute path if single quotes are
- help is det
- help(+What) is det
- Show help for What. What is a term that describes the
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
- 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
less program. This behaviour is controlled by the Prolog flag
help_pager. See section level documentation.
- See also
- - apropos/1 for searching the manual names and summaries.
- 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
- tty_width(-Width) is det[private]
- Return the believed width of the terminal. If we do not know Width
is bound to 80.
- current_predicate_help(?PI) is nondet[private]
- True when we have documentation on PI. First we decide we have a
definition for PI, then we check whether or not we have
documentation for the module in which PI resides. If not, we switch
to documentation collect mode and reload the file that defines PI.
- Send the current output of Goal through a pager. If no pager can be
found we simply dump the output to the current output.
- True when we believe to be running in Emacs. Unfortunately there is
no easy unambiguous way to tell.
- 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
dcg and aliases
non_terminal. For example:
- 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.