Left–leaning red–black trees. A general version and some customized to the key types "fixnum", "string" and "symbol" are provided.
A left-leaning red–black (LLRB) tree is a type of self-balancing binary search tree. It is a variant of the red–black tree and guarantees the same asymptotic complexity for operations.
This egg implements an API to LLRB-trees (mostly) compatible to srfi-69 Hashtables plus some procedures resembling the API of assoc-Lists.
Note that this egg is mainly intended to used to replace assoc-Lists.
- (make-llrb-treetype COMPARATOR) procedure
Define a treetype of keys matching COMPARATOR (from SRFI-128).
- (make-llrb-treetype KEY? EQUAL LESS) procedure
Define a treetype of keys matching the KEY? predicate using EQUAL as equivalence predicate and LESS as ordering predicate.
- (llrb-treetype? X) procedure
Test X to be an llrb-treetype.
The procedures "*binding-set*" have ananologous definitions specialized to the key type. Those specialized procedure names are prefixed by the key type (i.e. fixnum-, string- and symbol-).
Procedures prefixed with symbol-, fixnum-, string- are defined for most of the following. Those are specialized to the respective key type.
- (string-empty-binding-set) procedure
- (fixnum-empty-binding-set) procedure
- (symbol-empty-binding-set) procedure
- (empty-binding-set type) procedure
Return an empty binding set.
- (make-binding-set TYPE . pairs) procedure
Undocumented (API pending review).
Create an empty set of bindings of TYPE populate it with bindings from `pairs`.
- (binding-set-empty? set) procedure
Test whether or not the set has no associations.
- (binding-set-ref/default set key default) procedure
Returns the value bound to key in set or default value if not found.
- (binding-set-ref set key [failure] [success]) procedure
Extracts the value associated to key in "binding-set", invokes the procedure success on it, and returns its result; if success is not provided, then the value itself is returned. If key is not contained in set and failure is supplied, then failure is invoked on no arguments and its result is returned. Otherwise, it is an error.
- (binding-set-insert set key value) procedure
Extend set with a binding key-value, return the extended set.
- (binding-set-delete key set) procedure
Deletes association from set with given key, return the new set.
- (binding-set-update set key update default) procedure
Return a set with the binding of key replaced. update and default are procedures with the same semantics and in hash-table-update!.
- (binding-set-cons key value set) procedure
Same as binding-set-insert with API as alist-cons (srfi-1).
- (binding-set-fold proc nil set) procedure
Proc must be a procedure of three arguments. It is invoked for each element with the key, value and the accumulated value (nil for the first element).
- (binding-set-union inner outer) procedure
Return a merged set. All bindings in inner shadow those in outer.
- (make-table type) procedure
Create a table with an empty set of bindings according to type.
- (string-make-table) procedure
- (fixnum-make-table) procedure
- (symbol-make-table) procedure
Create a table with an empty set of bindings. Specialized to the key type.
- (table? x) procedure
Test whether or not the object is a LLRB-table.
- (table-empty? table) procedure
Test table to have no bidings.
- (table-copy table) procedure
Create a copy of table initially sharing all bindings.
- (table-delete! table key) procedure
Delete the binding for key from the bindings in the table.
- (table-set! table key value) procedure
Set the value for key in table.
- (table-ref/default table key default) procedure
Returns the value associated to key in table, or the default when the key is missing.
- (table-ref table key [failure] [success]) procedure
Extracts the value associated to key in table, invokes the procedure success on it, and returns its result; if success is not provided, then the value itself is returned. If key is not contained in set and failure is supplied, then failure is invoked on no arguments and its result is returned. Otherwise, it is an error.
- (table-update! table key update . default) procedure
Note: procedures update and default should have no side effects. They may be called multiple times. (This can happen if those procedures allow other continuations/threads to update the table before they return. As a consequence those procedures must especially not update the table, since this will result in an endless loop.)
- (table-fold table proc nil) procedure
- (table-for-each table proc) procedure
Intentionally minimum related operations are NOT available for symbol, since those are supposedly unordered.
- (table-min table thunk) procedure
Return two values the minimal key and associated value in table. If the table is empty thunk is invoked instead.
((FIXME: will be in constant time with little change to the source, at the moment O(log n).))
- (table-delete-min! table) procedure
Delete the entry with the smalles key and return two values, the key and associated value in table. In case table is empty returns two false values.
Note: These procedures are obsolete for chicken version >= 4.10.1 at least (they provide no more performance benefit) and will be removed in future versions of this egg.
- (wrap-one-string-arg PROC) procedure
Returns a procedure caching PROC. PROC must accept exactly one argument, a string.
- (str2sym string) procedure
Calls string->symbol and caches the result. (Surprisingly this is faster on lookup than string->symbol itself, at least for large numbers.)
#;1> (use llrb-tree) #;2> (define y (fixnum-make-table)) #;3> (fixnum-table-update! y 23 add1 (lambda () 41)) 42 #;4> (define numttype (make-llrb-treetype number? = <)) #;5> (define nt (make-table numttype)) #;6> (table-update! nt 42.23 add1 (lambda () 22)) 23 #;7> (define clsttype (make-llrb-treetype number? (lambda (a b) (let ((delta (- a b))) (and (< delta 1) (> delta 0)))) <)) #;8> (define ct (make-table clsttype)) #;9> (table-set! ct 1 '(one)) #;10> (table-set! ct 2 '(two)) #;11> (table-set! ct 3 '(three)) #;12> (define (classify n) (table-update! ct n (lambda (v) `(,(car v) ,n . ,(cdr v))))) #;13> (classify 1.1) (one 1.1) #;14> (classify 1.2) (one 1.2 1.1) #;15> (classify 2.1) (two 2.1) #;16> (classify 2.4) (two 2.4 2.1) #;17> (classify 3.5) (three 3.5) #;18> (table-fold ct (lambda (k v i) `((,k . ,v) . ,i)) '()) ((1 one 1.2 1.1) (2 two 2.4 2.1) (3 three 3.5)) #;19> (define (string-binding-set-find set proc) ;; This is not the most efficient implementation. (call-with-current-continuation (lambda (return) (or (string-binding-set-fold (lambda (k v i) (let ((hit (proc k v))) (if hit (return hit) i))) #f set) (error "no match"))))) #;20> (string-binding-set-find (string-binding-set-cons "a" 'A (string-empty-binding-set)) (lambda (k v) (equal? k "a"))) #t
Jörg F. Wittenberger
0.3.1.2 -- Minor fix: install llrb-tree.import.so instead of .scm file.
0.3.1 -- Enable srfi-128 comparators, add tests, documentation update.
0.3 -- Fixed dependency.
0.2 -- Changed API to match srfi-125
0.1 -- initial release
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