kvlists
Note: This is taken from the Chicken Wiki, where a more recent version could be available.
This egg provides keyword/value list (or key-value list, for short) operations. Key-value lists are a restricted subset of property lists wherein the key is always a self-evaluating keyword symbol.
In addition to key-value list manipulators, the egg also provides facilities for conversions between kvlists (key-value lists) and both plists (property lists) and alists (association lists).
Here's a run-down of the different ways to use Scheme lists for directly storing mappings/bindings:
(Self-evaluating keyword symbols are defined in SRFI-88: Keyword objects).
These examples assume Chicken is being run with -keyword-style suffix, which is the default mode. See the manual section Using the interpreter in case you wish to use prefix-style keywords as in Common Lisp.
#;1> (use kvlists) #;2> (define lst '(foo: 1 bar: 2 baz: 3)) #;3> (kvlist? lst) #t #;4> (kvlist-ref lst baz:) 3 #;5> (kvlist-ref lst abc:) #f #;6> (kvlist-ref lst abc: 123) 123 #;7> (kvlist->alist lst) ((foo . 1) (bar . 2) (baz . 3)) #;8> (kvlist->plist lst) (foo 1 bar 2 baz 3)
There are many opportunities to use key-value lists to cut down on the proliferation of parentheses in syntactic forms. While this may arguably be against the Lisp ethos, here's a straightforward let/kv macro which uses let to introduce lexically scoped variable bindings but without one layer of enclosing parentheses in the defining form:
(use kvlists)
(define-macro (let/kv head . body)
`(let ,(kvlist-map (lambda (k v) (list (keyword->symbol k) v))
head)
,@body))
(let/kv (x: 123 y: 456 z: 789)
(printf "x + y + z = ~A\n" (+ x y z)))
[procedure] (kvlist-cons* KEY VALUE KVLIST)
[procedure] (kvlist? X)
[procedure] (alist? X)
[procedure] (plist? X)
[procedure] (kvlist-key? KVLIST KEY)
[procedure] (kvlist-ref KVLIST KEY)
[procedure] (kvlist-assoc KEY KVLIST)
[procedure] (kvlist-map PROC KVLIST)
[procedure] (kvlist-for-each PROC KVLIST)
[procedure] (kvlist-delete KEY KVLIST)
[procedure] (kvlist-set! KVLIST KEY VALUE)
[procedure] (kvlist->alist KVLIST)
[procedure] (kvlist->plist KVLIST)
[procedure] (alist->kvlist ALIST)
[procedure] (alist->plist ALIST)
[procedure] (plist->kvlist PLIST)
[procedure] (plist->alist PLIST)
[procedure] (keyword->symbol KEYWORD)
[procedure] (symbol->keyword SYMBOL)
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