modules.pl -- Module utility predicates

 in_temporary_module(?Module, :Setup, :Goal)

Run Goal on temporary loaded sources and discard the module and loaded predicates after completion. This predicate performs the following steps:

1. If Module is unbound, create a unique identifier for it.
2. Turn Module into a temporary module using set_module/1. Note that this requires the module to be non-existent or empty. If Module is specified, it should typically be set to a unique value as obtained from e.g. uuid/1.
3. Run Setup in the context of Module.
4. If setup succeeded possible choice points are discarded and Goal is started.

The logical result of this predicate is the same as `(Setup@Module -> Goal@Module)`, i.e., both Setup and Goal are resolved relative to the current module, but executed in the context of Module. If Goal must be called in Module, use call(Goal).

The module and all its predicates are destroyed after Goal terminates, as defined by setup_call_cleanup/3.

Discussion This predicate is intended to load programs in an isolated environment and reclaim all resources. This unfortunately is incomplete:

• Running the code may leave side effects such as creating records, flags, changing Prolog flags, etc. The system has no provisions to track this.
• So called functors (name/arity pairs) are not yet subject to garbage collection. Functors are both used to define predicates and to create compound terms.

See also

- library(sandbox) determines whether unknown goals are safe to call.

- load_files/2 offers the option sandboxed(true) to load code from unknown sources safely.

 current_temporary_module(-Module) is semidet

True when we are executing in the given temporary module context.