Node:Load Predicates, Next:Declarations, Previous:Load Intro, Up:Load Intro
This section contains a summary of the relevant predicates. For a more precise description, see Read In.
To consult a program, issue the query:
| ?- consult(Files).
where Files is either a filename or a list of filenames, instructs
the processor to read in the program which is in the files. For
example:
| ?- consult([dbase,'extras.pl',user]).
When a directive is read it is immediately executed. Any predicate
defined in the files erases any clauses for that predicate already
present. If the old clauses were loaded from a different file than the
present one, the user will be queried first whether (s)he really wants
the new definition. However, if a multifile declaration
(see Declarations) is read and the corresponding predicate exists
and has previously been declared as multifile, new clauses will
be added to the predicate, rather than replacing the old clauses. If
clauses for some predicate appear in more than one file, the later set
will effectively overwrite the earlier set. The division of the program
into separate files does not imply any module structure--any predicate
can call any other (see Module Intro).
consult/1, used in conjunction with save_program/[1,2] and
restore/1, makes it possible to amend a program without having to
restart from scratch and consult all the files which make up the
program. The consulted file is normally a temporary "patch" file
containing only the amended predicate(s). Note that it is possible to
call consult(user) and then enter a patch directly on the
terminal (ending with ^D). This is only recommended for small,
tentative patches.
| ?- [File|Files].
This is a shorthand way of consulting a list of files. (The case where there is just one filename in the list was described earlier (see Reading In).
To compile a program in-core, use the built-in predicate:
| ?- compile(Files).
where Files is specified just as for consult/1.
The effect of compile/1 is very much like that of
consult/1, except all new procedures will be stored in compiled
rather than consulted form. However, predicates declared as dynamic
(see below) will be stored in consulted form, even though
compile/1 is used.
Programs can be compiled into an intermediate representation known as
.ql (for Quick Load file). As of SICStus Prolog 3.8, this
feature is obsolescent with the introduction of partial saved states
(.po files; see Saving), which can be handled much more efficiently.
To compile a program into a .ql file, use the built-in predicate:
| ?- fcompile(Files).
where Files is specified just as for consult/1. For each
filename in the list, the compiler will append the suffix .pl to it
and try to locate a source file with that name and compile it to a .ql
file. The filename is formed by appending the suffix .ql to
the specified name. The internal state of SICStus Prolog is not changed as
result of the compilation. See Considerations.
To load a program from a set of source or object files, use the built-in
predicates load_files/[1,2] (the latter is controlled by an options list):
| ?- load_files(Files).
where Files is either a single filename or a list of filenames,
optionally with .pl or .po or .ql extensions.
This
predicate takes the following action for each File in the list of
filenames:
user, compile(user) or [user] is
performed;
.po file is found, the file is loaded;
.ql file is found, the file is loaded;
load_files/1 was called
from a directive of a file being consulted.
Finally, to ensure that some files have been loaded, use the
built-in predicate:
| ?- ensure_loaded(Files).
Same as load_files(Files), except if the file to be loaded
has already been loaded and has not been modified since that time,
in which case the file is not loaded again. If a source file has been
modified, ensure_loaded/1 does not cause any object file to
become recompiled.