SWI-Prolog -- prolog_file

prolog_file_type(?Extension, ?Type)

This dynamic multifile predicate defined in module user determines the extensions considered by file_search_path/2. Extension is the filename extension without the leading dot, and Type denotes the type as used by the file_type(Type) option of file_search_path/2. Here is the initial definition of prolog_file_type/2:

user:prolog_file_type(pl,       prolog).
user:prolog_file_type(Ext,      prolog) :-
        current_prolog_flag(associate, Ext),
        Ext \== pl.
user:prolog_file_type(qlf,      qlf).
user:prolog_file_type(Ext,      executable) :-
        current_prolog_flag(shared_object_extension, Ext).

Users can add extensions for Prolog source files to avoid conflicts (for example with perl) as well as to be compatible with another Prolog implementation. We suggest using .pro for avoiding conflicts with perl. Overriding the system definitions can stop the system from finding libraries.