file_search_path/2 hook:- multifile user:file_search_path/2.
user:file_search_path(+PathAlias, +DirSpec)
Defines a symbolic name for a directory or a path. Used by predicates taking file_spec as input argument.
atom
An atom that represents the path given by DirSpec.
file_spec
Either an atom giving the path to
a file or directory, or PathAlias(DirSpec), where PathAlias is
defined by another file_search_path/2 rule.
The file_search_path mechanism provides an extensible way of
specifying a sequence of directories to search to locate a file. For
instance, if a filename is given as a structure term,
library(between). The principle functor of the term, library,
is taken to be another file_search_path/2 definition of the form
file_search_path(library, LibPath)
and file between is assumed to be relative to the path given by
LibPath.
LibPath may also be another structure term, in which case another
file_search_path/2 fact gives its definition. The search continues
until the path is resolved to an atom.
There may also be several definitions for the same PathAlias. Certain
predicates, such as load_files/[1,2] and absolute_file_name/[2,3],
search all these definitions until the path resolves to an existing file.
There are several predefined search paths, such as
application, runtime, library, system.
These are tried before the user-defined ones.
The predicate is undefined at startup, but behaves as if it were a
multifile predicate with the following
clauses. The system properties SP_APP_DIR and
SP_RT_DIR expand respectively to the absolute path of the
directory that contains the executable and the directory that contains
the SICStus runtime (see System Properties and Environment Variables), SP_TEMP_DIR expand to a directory suitable for
storing temporary files.
file_search_path(library, Path) :-
library_directory(Path).
file_search_path(system, Platform) :-
prolog_flag(host_type, Platform).
file_search_path(application, '$SP_APP_DIR').
file_search_path(runtime, '$SP_RT_DIR').
file_search_path(temp, '$SP_TEMP_DIR').
file_search_path(path, Dir) :-
… backtracks through the $PATH environment variable …
| ?- [user].
% compiling user...
| :- multifile user:file_search_path/2.
| user:file_search_path(home, '/usr/joe_bob').
| user:file_search_path(review, home('movie/review')).
| end_of_file.
% compiled user in module user, 0 msec 768 bytes
yes
| ?- compile(review(blob)).
% compiling /usr/joe_bob/movie/review/blob.pl
All error handling is done by the predicates extended by this hook.
absolute_file_name/[2,3],
library_directory/1,
load_files/[1,2],
ref-fdi, ref-lps-flg,
System Properties and Environment Variables.