v2.4.0: CHAMP bags; and book coming!

[slburson]

The first big news for v2.4.0 is that bags now have a CHAMP implementation, which is the default if you're using the fset2 package.

The other big news is that my online book, Modern Common Lisp with FSet, is almost complete! Have a look at the current draft. It has detailed API docs for all the FSet types, including the new CHAMP bags.

In the course of writing the book, I found many small things to fix or improve in the code; there's really nothing like documenting something to bring its flaws to one's attention, is there? Here they are, in roughly decreasing order of significance:

• Bug fix: do-seq did not correctly handle both from-end? and index? being true.

• Bug fix: a char seq with a non-nil default did not print with a default suffix.

• Bug fixes on GMap result types: bag-sum now returns the empty bag on zero bags, rather than nil; bag-product now returns the full set in this case (it is the identity element for bag-product); map-union and map-intersection now do defaulting correctly.

• Bug fix: the rereading seq reader did not yet understand the new print syntax for runs of characters within a seq.

• Bug fixes: tuples and binary relations did not have their read memory barriers (for multithreading) in exactly the right places.

• Bug fix: calling inverse on an empty binary relation did not cause the inverse to be incrementally maintained thereafter.

• Minor incompatible change: arb on an empty bag now returns a second value of 0.

• Potentially incompatible change: FSet/Iterate now builds CHAMP sets, bags, and maps by default.

• FSet/Jzon parsing, in tuple mode, converts null back to nil; it also converts the empty seq back to nil if the key is of list type.

• New operations (fset2: only): map-difference.

• New methods: domain-contains? and range-contains? on a 2-relation; fun-iterator on replay-set and replay-map; make-load-form on wb-replay-set, ch-replay-set, wb-replay-map, ch-replay-map.

• New setf expander: default (functional, of course).

• New modify macros: clear-default, map-imagef.

• contains? on a bag now accepts an optional multiplicity, defaulting to 1; asks whether the bag contains at least that many occurrences of the value.

• reduce on a bag now has an additional keyword parameter pairs?; if true, the function is called only once per unique element, with the multiplicity passed as the second argument.

• New method at-index on a seq, synonymous with lookup.

• (convert ((eql seq) replay-map)) now has a keys-only? keyword parameter; if true, it returns the key sequence in O(1) time.

• Taking size of a complement-set is now an error. (It used to return the negative of the size of the complemented set, which almost made a cute kind of sense -- it harked back to Zeta-C's treatment of unsigned arbitrary-precision integers, which treated all negative numbers as greater than all positive ones. Unfortunately, it had an off-by-one error: even in this rather creative interpretation, the size of the full set should have been represented as -1, not 0.)

• I added methods on bag-product for bag and complement-set, since the full set is actually the identity element for bag-product, as it contains every value with multiplicity 1; and GMap result type bag-product now returns the full set on zero bags.

• Added some missing exports (to both packages): fun-iterator, complement-set, complement-set?.

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This discussion was created from the release v2.4.0: CHAMP bags; and book coming!.