Debugging often requires interaction with predicates that reside in modules: running them, setting spy points on them, etc. This can be achieved using the <module>:<term> construct explicitly as described above. In SWI-Prolog, you may also wish to omit the module qualification. Setting a spy point (spy/1) on a plain predicate sets a spy point on any predicate with that name in any module. Editing (edit/1) or calling an unqualified predicate invokes the DWIM (Do What I Mean) mechanism, which generally suggests the correct qualified query.
Mainly for compatibility, we provide module/1 to switch the module with which the interactive top level interacts:
module(Module) may be used to switch
the default working module for the interactive top level (see prolog/0).
This may be used when debugging a module. The example below lists the
clauses of file_of_label/2
in the module tex.
1 ?- module(tex). true. tex: 2 ?- listing(file_of_label/2). ...