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consideration is what extension to use for the source files. Tradition
.pl, but conflicts with Perl force the use of
another extension on systems where extensions have global meaning, such
as MS-Windows. On such systems
.pro is the common
alternative. On MS-Windows, the alternative extension is stored in the
versions of SWI-Prolog load files with the extension
well as with the registered alternative extension without explicitly
specifying the extension. For portability reasons we propose the
.proand use this extension for the files you want to load through your file manager. Use
.plfor all other files for maximal portability.
Large projects are generally composed of sub-projects, each using its own directory or directory structure. If nobody else will ever touch your files and you use only one computer, there is little to worry about, but this is rarely the case with a large project.
To improve portability, SWI-Prolog uses the POSIX notation for
filenames, which uses the forward slash (
separate directories. Just before reaching the file system, SWI-Prolog
to convert the filename to the conventions used by the hosting operating
system. It is strongly advised to write paths using the
especially on systems using the
for this purpose (MS-Windows). Using
violates the portability rules and requires you to double the
due to the Prolog quoted-atom escape rules.
Portable code should use prolog_to_os_filename/2 to convert computed paths into system paths when constructing commands for shell/1 and friends.
Thanks to Quintus, Prolog adapted an extensible mechanism for searching files using file_search_path/2. This mechanism allows for comfortable and readable specifications.
Suppose you have extensive library packages on graph algorithms, set operations and GUI primitives. These sub-projects are likely candidates for re-use in future projects. A good choice is to create a directory with sub-directories for each of these sub-projects.
Next, there are three options. One is to add the sub-projects to the directory hierarchy of the current project. Another is to use a completely dislocated directory. Third, the sub-project can be added to the SWI-Prolog hierarchy. Using local installation, a typical file_search_path/2 is:
:- prolog_load_context(directory, Dir), asserta(user:file_search_path(myapp, Dir)). user:file_search_path(graph, myapp(graph)). user:file_search_path(ui, myapp(ui)).
When using sub-projects in the SWI-Prolog hierarchy, one should use
the path alias
swi as basis. For a system-wide
installation, use an absolute path.
Extensive sub-projects with a small well-defined API should define a load file with calls to use_module/1 to import the various library components and export the API.