Many messages refer to a predicate. Rather than formatting the
predicate indicator yourself, use the grammar rules below. They are
defined in the system module $messages and are declared
public, i.e., they must be called with an explicit module
qualification. Using them makes the reference consistent with the
messages of the system: the predicate indicator is written using the
code style class and, if the source location of the
predicate is known, it becomes a hyperlink to its definition on
terminals that support this (see section
2.5 and the Prolog flag
hyperlink_term). This works for predicates defined in C as well,
provided the system can resolve the address of the implementing
function.
prolog:message(no_such_predicate(PI)) -->
[ 'There is no ' ],
'$messages':predicate_reference(PI).
- predicate_reference(+Spec)
//
- predicate_reference(+Spec,
+Options)
// - Emit a reference to a predicate. Spec is a (possibly module
qualified) head or predicate indicator. Non-terminals are printed using
the
// notation. Options:
- module(Which)
- One of
auto (default), hide or show.
Using
auto, the module qualification is removed if it is user,
system or a system internal module.
- link(Bool)
- If
false, do not create a hyperlink. Default is true.
- style(Class)
- Style class for the reference. Default is
code.
- tag(Bool)
- If
true, add a tag that indicates the kind of the
predicate. Default is false. This is intended for messages
that list candidate predicates, one per line.
- predicate_definition(+Spec,
+Message)
// - Emit “Message at File:Line”
on a new line if the location of Spec is known and nothing at
all if it is not.
- [semidet]predicate_kind(+Spec,
-Kind)
- Classify a predicate as
iso, built_in, foreign,
library(Name), module(Module), user
or
undefined. This is the classification used by the
tag(true) option above. Fails if Spec does not
denote a predicate.
