ASDF is a popular “system construction tool”. The package
slime-asdf
provides some commands to load and compile such
systems from Emacs. ASDF itself is not included with
SLIME; you have to load that yourself into your Lisp. In
particular, you must load ASDF before you connect, otherwise
you will get errors about missing symbols.
The package also installs some new REPL shortcuts (see Shortcuts):