4.11.1.1 Referring to predicates from a message

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.