I meet the following error. Any clue?
CL-USER> (require "asdf") NIL
But the page https://common-lisp.net/project/asdf/asdf.html#Loading-ASDF said
The recommended way to load ASDF is via:
(require "asdf") All actively maintained Lisp implementations now include a copy of ASDF 3 that you can load this way using Common Lisp’s require function.1
The specification for PROVIDE, REQUIRE says that the return value of require is implementation-dependant, but that it should signal an error if a module fails to be loaded. In your case, the NIL return value is not an error, but an indication that the operation succeeded.
Try (asdf:make "optima"), for example. Your environment should recognize the ASDF:MAKE symbol, but it might fail to load the :optima system. See Quicklisp to download and install systems.
By the way, you rarely need to require asdf (you don't need to do it in SBCL nor in CCL, at least). To be sure, you might want to restart your Lisp environment and see if the ASDF package exists.
