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
following values:
- false
- Never use a pager.
- default
- 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 less
program.
- Callable
- 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.
- [det]help
- [det]help(+What)
- Show help for What. What is a term that describes
the
topics(s)
to give help for. Notations for What
are:
- Atom
- This ambiguous form is most commonly used and shows all matching
documents. For example:
?- help(append).
- 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)
- Module
:
Name - Give help on predicates with Name in Module and
any arity. Used for loaded code only.
- Module
:
Name/Arity
- Give help on predicates with Name in Module and Arity.
Used for loaded code only.
- f(Name/Arity)
- Give help on the matching Prolog arithmetic functions.
- c(Name)
- Give help on the matching C interface function
- section(Label)
- Show the section from the manual with matching Label.
help/1 shows
documentation from the manual as well as from loaded user code if the
code is documented using PlDoc. To show only the documentatoion of the
loaded predicate we may prefix predicate indicator with the module in
which it is defined.
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.
- [semidet,multifile]show_html_hook(+HTML:string)
- 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.
- [det]apropos(+Query)
- Print objects from the manual whose name or summary match with
Query. Query takes one of the following forms:
- Type
:
Text - Find objects matching Text and filter the results by Type.
Type matching is a case intensitive prefix match.
Defined types are
section
, cfunction
, function
,
iso_predicate
, swi_builtin_predicate
, library_predicate
,
dcg
and aliases chapter
, arithmetic
, c_function
,
predicate
, nonterminal
and non_terminal
.
For example:
?- apropos(c:close).
?- apropos(f:min).
- Text
- 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.