While the statement is correct, it hides a problem that can cause a new user some confusion and needs a bit of clarification. The problem is not with the quoted statement but the wording used in the SWI-Prolog documentation.
Currently the way I think of SWI-Prolog code posted at the GitHub repository is of several parts.
- The low-level C code which is typically in the /src directory
- The core Prolog code which is typically in /boot
- The libraries of Prolog code which is typically in /library
- The packages such as ODBC which are listed in /packages but the code is in separate repositories under the main SWI-Prolog repository, e.g. packages-odbc. These are selected during the build. When installing SWI-Prolog on Windows with the Wizard they are also referred to as components. (ref)
- Packs - which are add-ons and not in the SWI-Prolog repository. These are installed once SWI-Prolog is running.
The key thing to point out is that sometimes Packs are noted as Packages and that can be confusing. e.g.
If you do a Google search for SWI-Prolog packages you will most likely find the packs instead of the packages.
I only understood it when I was corrected for something I wrote in a post and then I took the time to understand it. See: Library, packages and packs?