https://github.com/VincentToups/persistent-tables.git
git clone 'https://github.com/VincentToups/persistent-tables.git'
(ql:quickload :persistent-tables)
This is a dead simple implementation of persistent hash tables on top of a port of David Va Horn's persistent random-access lists, SRFI-101.
These are like hash tables in most respects, with similar, but not
identical performance profiles, with the major exception that
modification is functional, ptbl-set returns a new hash table with
the new association in it. The previous table is left unmodified.
(setq tbl ({} the-empty-ptbl :x 10))
(ptbl-get tbl :x) -> 10
(ptbl-get the-empty-ptbl :x) -> nil
The function {} allows you to quickly create a new ptbl or to update
the associations in a ptbl, when the first argument is itself a
ptbl. Eg:
({} :x 10 :y 11)
Creates a new ptbl with :x and :y associations.
({} a-table :x 10 :y 11)
Returns a new ptbl with the same associations as a-table except
where :x and :y are concerned.