diff options
| -rw-r--r-- | eval.c | 2 | ||||
| -rw-r--r-- | txr.1 | 68 |
2 files changed, 69 insertions, 1 deletions
@@ -5801,6 +5801,8 @@ void eval_init(void) reg_fun(intern(lit("copy-alist"), user_package), func_n1(copy_alist)); reg_fun(intern(lit("prop"), user_package), func_n2(getplist)); reg_fun(intern(lit("memp"), user_package), func_n2(memp)); + reg_fun(intern(lit("plist-to-alist"), user_package), func_n1(plist_to_alist)); + reg_fun(intern(lit("improper-plist-to-alist"), user_package), func_n2(improper_plist_to_alist)); reg_fun(intern(lit("merge"), user_package), func_n4o(merge_wrap, 2)); reg_fun(intern(lit("sort"), user_package), func_n3o(sort, 1)); reg_fun(intern(lit("shuffle"), user_package), func_n1(shuffle)); @@ -18184,11 +18184,36 @@ function applied to the corresponding element of the input list. .SS* Property Lists -A property list a flat list of even length consisting of interleaved +A +.IR "property list", +also referred to as a +.IR plist , +is a flat list of even length consisting of interleaved pairs of property names (usually symbols) and their values (arbitrary objects). An example property list is (:a 1 :b "two") which contains two properties, :a having value 1, and :b having value "two". +An +.I "improper plist" +represents Boolean properties in a condensed way, as property +indicators which are not followed by a value. Such properties +only indicate their presence or absence, which is useful for +encoding a Boolean value. If it is absent, then the property +is false. Correctly using an improper plist requires that the +exact set of Boolean keys is established by convention. + +In this document, the unqualified terms +.I "property list" +and +.I "plist" +refer strictly to an ordinary plist, not to an improper plist. + +.TP* "Dialect Note:" + +Unlike in some other Lisp dialects, including ANSI Common Lisp, +symbols do not have property lists in \*(TL. Improper plists +aren't a concept in ANSI CL. + .coNP Function @ prop .synb .mets (prop < plist << key ) @@ -18249,6 +18274,47 @@ function, harmonizing with functions in the .code member family. +.coNP Functions @ plist-to-alist and @ improper-plist-to-alist +.synb +.mets (plist-to-alist << plist ) +.mets (improper-plist-to-alist < imp-plist << bool-keys ) +.syne +.desc +The functions +.code plist-to-alist +and +.code improper-plist-to-alist +convert, respectively, a property list and improper property +list to an association list. + +The +.code plist-to-alist +function scans +.meta plist +and returns the indicator-property pairs as a list of cons +cells, such that each +.code car +is the indicator, and each +.code cdr +is the value. + +The +.code improper-plist-to-alist +is similar, except that it handles the Boolean properties +which, by convention, aren't followed by a value. The list of +all such indicators is specified by the +.code bool-keys +argument. + +.TP* "Examples:" +.cblk + (plist-to-alist '(a 1 b 2)) --> ((a . 1) (b . 2)) + + (improper-plist-to-alist '(:x 1 :blue :y 2) '(:blue)) + --> ((:x . 1) (:blue) (:y . 2)) +.cble + + .SS* List Sorting Note: these functions operate on lists. The principal sorting function |