These are Dyalog's dfns used for processing tree structures. Their original source is Dyalog's tree processing dfns page. They are included in April's demo test suite, so you can run tests of these functions by first evaluating (april:load-libs) to load the functions and then (april:run-tests) to run the tests.
Note that some of these functions cannot be compiled under ABCL; the JVM imposes a limit on the size of compiled methods that ABCL cannot mitigate, and some of the large functions in this library exceed that limit.