The pfds package contain implementations of immutable, persistent
data structures. The implementations are mostly based on Chris Okasaki's
book Purely Functional Data Structures.
The pfds package is located under the pkgsrc directory
in the Slogan source tree. You can install it from the REPL using the install_package
function:
install_package("pfds", 'local, "/path_to_slogan_src/pkgsrc/pfds")
Once installed, the package can be loaded to a program by calling the load_package
function.