:- multifile +PredSpecs
Allows the clauses for the specified predicates to be in more than one file.
A built-in prefix operator, so that declarations can be written as e.g.
:- multifile a/1, b/3.
By default, all clauses for a predicate are expected to come from just
one file. This assists with reloading and debugging of code.
Declaring a predicate
multifile means that its clauses can be
spread across several different files. This is independent of whether
or not the predicate is declared
Should precede all the clauses for the specified predicates in the file.
There should be a
multifile declaration for a predicate P
in every file that contains clauses for P. This restriction is
not currently enforced in the Development System: for compatibility
with earlier releases it suffices to have a
in the first file loaded that contains clauses for P. However,
a warning is noted if the
multifile declaration is omitted in
subsequent files. The
multifile declarations must be
included in every file when
qpc is being used to compile files
multifile predicate is dynamic, there should be a
declaration in every file containing clauses for the predicate. Again, this is
not enforced in the Development System, for backwards compatibility, but
warnings are printed if the
dynamic declarations are omitted.
dynamic declarations may not be omitted when
qpc is being used to
compile files separately.
When a file containing clauses for a
multifile predicate (P) is
reloaded, the clauses for P that previously came from that file are
removed. Then the new clauses for P (which may be the same as the old
ones) are added to the end of the definition of the
An exception to this is when the file concerned is the pseudo-file
meaning that clauses are being entered from the terminal; in this case the
clauses are always added to the end of the predicate without removing any
previously defined clauses.
multifile declaration is found for a predicate that has already been
defined in another file (without a
multifile declaration), then this is
considered to be a redefinition of that predicate. Normally this will result
in a multiple-definition style-check warning (see
source_file/2 can be used to find all the files containing
clauses for a
multifile predicates can be extended at run-time using
multifile/1 cannot be called as a built-in predicate. It can only be used
as a declaration to the compiler in a Prolog source file.