4.3 Loading Prolog source files
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Availability:built-in
Sourceensure_loaded(:File)
If the file is not already loaded, this is equivalent to consult/1. Otherwise, if the file defines a module, import all public predicates. Finally, if the file is already loaded, is not a module file, and the context module is not the global user module, ensure_loaded/1 will call consult/1.

With this semantics, we hope to get as close as possible to the clear semantics without the presence of a module system. Applications using modules should consider using use_module/[1,2].

Equivalent to load_files(Files, [if(not_loaded)]).54On older versions the condition used to be if(changed). Poor time management on some machines or copying often caused problems. The make/0 predicate deals with updating the running system after changing the source code.