The GNU SETL Om gives a brief overview of SETL and GNU SETL, and can be regarded as the top of the documentation tree. It also gives links to various external SETL resources.
The setl command and relatives are partly self-describing through the --help and --version options, but for full details on command invocation, relevant environment variables, and the provisions for making GNU SETL programs comfortable in and as scripts, please refer to the GNU SETL User Guide.
For a tutorial introduction to the SETL language, see the GNU SETL Language Tutorial [stub].
For a reference treatment of the language supported by GNU SETL, see the GNU SETL Language Reference [stub].
For detailed semantic information on the built-in operators and functions of GNU SETL, see the GNU SETL Library Reference.
For commentary on the internal interfaces and implementation of GNU SETL, see the GNU SETL Implementation Notes [stub].
For how to extend GNU SETL with datatypes and intrinsic functions derived from C headers and libraries, see the GNU SETL Extension Guide [stub].
And if you are a developer helping to maintain GNU SETL, please see the GNU SETL Maintenance Manual [stub].
The above documents are also available bundled as “zip” archives of HTML, PDF, and Info files. If you unpack such an archive into a given folder, the cross-references between documents allow for easy local navigation, even between PDFs.
The latest GNU SETL releases, including documentation, should always be available on the GNU SETL web site.