This module implements listing code from the internal representation in a human readable format.
- listing/0 lists a module.
- listing/1 lists a predicate or matching clause
- listing/2 lists a predicate or matching clause with options
- portray_clause/2 pretty-prints a clause-term
?- list_settings(listing). ======================================================================== Name Value (*=modified) Comment ======================================================================== listing:body_indentation 4 Indentation used goals in the body listing:tab_distance 0 Distance between tab-stops. ...
- Lists all predicates defined in the calling module. Imported
predicates are not listed. To list the content of the module
mymodule, use one of the calls below.
?- mymodule:listing. ?- listing(mymodule:_).
- listing(:What) is det
- listing(:What, +Options) is det
- List matching clauses. What is either a plain specification or a
list of specifications. Plain specifications are:
- Predicate indicator (Name/Arity or Name//Arity) Lists the indicated predicate. This also outputs relevant declarations, such as multifile/1 or dynamic/1.
- A Head term. In this case, only clauses whose head
unify with Head are listed. This is illustrated in the
query below that only lists the first clause of append/3.
?- listing(append(, _, _)). lists:append(, L, L).
The following options are defined:
- One of
source, for each clause that is associated to a source location the system tries to restore the original variable names. This may fail if macro expansion is not reversible or the term cannot be read due to different operator declarations. In that case variable names are generated.
false), extract the lines from the source files that produced the clauses, i.e., list the original source text rather than the decompiled clauses. Each set of contiguous clauses is preceded by a comment that indicates the file and line of origin. Clauses that cannot be related to source code are decompiled where the comment indicates the decompiled state. This is notably practical for collecting the state of multifile predicates. For example:
?- listing(file_search_path, [source(true)]).
- portray_clause(+Clause) is det
- portray_clause(+Out:stream, +Clause) is det
- portray_clause(+Out:stream, +Clause, +Options) is det
- Portray `Clause' on the current output stream. Layout of the
clause is to our best standards. As the actual variable names
are not available we use A, B, ... Deals with ';', '|', '->' and
calls via meta-call predicates as determined using the predicate
property meta_predicate. If Clause contains attributed
variables, these are treated as normal variables.
If Options is provided, the option-list is passed to write_term/3 that does the final writing of arguments.