SWI-Prolog 8.4.0 Reference Manual: Section 6.15

## 6.15 Module properties

The following predicates can be used to query the module system for reflexive programming:

[nondet]current_module(?Module)
  True if Module is a currently defined module. This predicate enumerates all modules, whether loaded from a file or created dynamically. Note that modules cannot be destroyed in the current version of SWI-Prolog.
module_property(?Module, ?Property)
  True if Property is a property of Module. Defined properties are:
  class(-Class)
    True when Class is the class of the module. Defined classes are
    user
      Default for user-defined modules.
    system
      Module `system` and modules from `<home>/boot`.
    library
      Other modules from the system directories.
    temporary
      Module is temporary.
    test
      Modules that create tests.
    development
      Modules that only support the development environment.
  file(?File)
    True if Module was loaded from File.
  line_count(-Line)
    True if Module was loaded from the N-th line of file.
  exports(-ListOfPredicateIndicators)
    True if Module exports the given predicates. Predicate indicators are in canonical form (i.e., always using name/arity and never the DCG form name//arity). Future versions may also use the DCG form. See also predicate_property/2. Succeeds with an empty list if the module exports no predicates.
  exported_operators(-ListOfOperators)
    True if Module exports the given operators. Each exported operator is represented as a term `op(Pri,Assoc,Name)`. Succeeds with an empty list if the module exports no operators.
  size(-Bytes)
    Total size in bytes used to represent the module. This includes the module itself, its (hash) tables and the summed size of all predicates defined in this module. See also the `size(Bytes)` property in predicate_property/2.
  program_size(-Bytes)
    Memory (in bytes) used for storing the predicates of this module. This figure includes the predicate header and clauses.
  program_space(-Bytes)
    If present, this number limits the `program_size`. See set_module/1.
  last_modified_generation(-Generation)
    Integer expression the last database generation where a clause was added or removed from a predicate that is implemented in this module. See also predicate_property/2.
set_module(:Property)
  Modify properties of the module. Currently, the following properties may be modified:
  base(+Base)
    Set the default import module of the current module to Module. Typically, Module is one of `user` or `system`. See section 6.10.
  class(+Class)
    Set the class of the module. See module_property/2.
  program_space(+Bytes)
    Maximum amount of memory used to store the predicates defined inside the module. Raises a permission error if the current usage is above the requested limit. Setting the limit to 0 (zero) removes the limit. An attempt to assert clauses that causes the limit to be exceeded causes a `resource_error(program_space)` exception. See assertz/1 and module_property/2.