>From cebb9a88e244457428385948eaf6bac24a7e5eb1 Mon Sep 17 00:00:00 2001 From: akater Date: Wed, 15 Sep 2021 19:42:47 +0000 Subject: [PATCH] Add cl-map-into map-into is a standard Common Lisp function that acts as cl-map, only values are recorded into a preallocated sequence. * lisp/emacs-lisp/cl-extra.el (cl-map-into): New primary function (cl--map-into-basic-call-arguments-limit, cl--map-into-max-small-signature): New auxiliary constant (cl--map-into-mappers-array, cl--map-into-mappers-alist): New variable (cl--compute-map-into-signature, cl--make-map-into-mapper): New auxiliary function (cl--do-seq-type-signature): New auxiliary macro --- doc/misc/cl.texi | 9 ++ etc/NEWS | 7 + lisp/emacs-lisp/cl-extra.el | 206 +++++++++++++++++++++++++ test/lisp/emacs-lisp/cl-extra-tests.el | 61 ++++++++ 4 files changed, 283 insertions(+) diff --git a/doc/misc/cl.texi b/doc/misc/cl.texi index 04e2c71a2b..45cea26d4e 100644 --- a/doc/misc/cl.texi +++ b/doc/misc/cl.texi @@ -3301,6 +3301,15 @@ be one of the following symbols: @code{vector}, @code{string}, thrown away and @code{cl-map} returns @code{nil}). @end defun +@defun cl-map-into result-sequence function &rest sequences +This function is like @code{cl-map}, except that the values returned by +@var{function} are recorded into existing @var{result-sequence} rather +than into a newly allocated sequence of specified type. Note also that +while @code{cl-map} requires the function to be mapped over to accept at +least one argument, @code{cl-map-into} does not require that from +@var{function}. The return value is @var{result-sequence}. +@end defun + @defun cl-maplist function list &rest more-lists This function calls @var{function} on each of its argument lists, then on the @sc{cdr}s of those lists, and so on, until the diff --git a/etc/NEWS b/etc/NEWS index b91a5cbb72..131df75df4 100644 --- a/etc/NEWS +++ b/etc/NEWS @@ -157,6 +157,13 @@ Using 'make-obsolete' on a theme is now supported. This will make ** New function 'define-keymap'. This function allows defining a number of keystrokes with one form. ++++ +** New function 'cl-map-into'. +A counterpart of Common Lisp's 'map-into', this function destructively +modifies a sequence passed to it to contain the results of applying a +function passed to it to each element in the sequences passed to it, +in turn. + +++ ** New macro 'defvar-keymap'. This macro allows defining keymap variables more conveniently. diff --git a/lisp/emacs-lisp/cl-extra.el b/lisp/emacs-lisp/cl-extra.el index 499d26b737..df712e3237 100644 --- a/lisp/emacs-lisp/cl-extra.el +++ b/lisp/emacs-lisp/cl-extra.el @@ -88,6 +88,212 @@ defun cl-equalp (x y) (t (equal x y)))) +;;; map-into + +;; We implement a simple dispatcher for sequence types. +;; +;; cl-extra has cl--mapcar-many for similar purpose. +;; The core issue with it, it goes through args pre-emptively +;; to compute min length when there are more than 2 arguments +;; which makes it and its reverse dependencies fail on circular lists +;; unless there are <3 args. +;; Other issues are +;; - it performs type checks for sequences of known types at runtime +;; - it may cons whole arglist thrice per invocation +;; - looks like it's hard to extend. + +;; Our approach doesn't have these issues. + +(defconst cl--map-into-basic-call-arguments-limit 7 + "Maximal reasonably expected number of arguments to `cl-map-into'. + +`cl-map-into' caches its code corresponding to various signature +types of arglists supplied to `cl-map-into'. Arglists may vary +in length. + +Code corresponding to arglists of length less than +`cl--map-into-basic-call-arguments-limit' is accessed via array. + +Code corresponding to arglists of length greater than or equal to +`cl--map-into-basic-call-arguments-limit' is accessed via alist.") + +(defconst cl--map-into-max-small-signature + (expt 2 cl--map-into-basic-call-arguments-limit) + "Length of array to allocate for caching `cl-map-into' mappers +corresponding to small arglists. + +Such mappers are accessed by their position in an array; position +equals the signature. + +Consider `cl-map-into' arglist + +(result-seq f seq-1 seq-2) + +call-arguments-limit corresponding to arglists of this length or +shorter, is 4 (as there are 4 arguments). This leaves at most 3 +sequences to contribute to type signature. + +Hovewer, we have to store one additional bit for fixnum-based +encoding to be unambiguous and simple. So overall array length +ends up being exactly (expt 2 call-arguments-limit).") + +(defvar cl--map-into-mappers-array + (make-vector cl--map-into-max-small-signature nil) + "Array holding mappers corresponding to small arglists of `cl-map-into'. + +Element type is (or function null).") + +(defvar cl--map-into-mappers-alist nil + "Alist holding mappers corresponding to large arglists of `cl-map-into'.") + +(defun cl--compute-map-into-signature (&rest all-sequences) + "Compute lookup key for `cl-map-into''s almost-arglist ALL-SEQUENCES. + +Namely: ALL-SEQUENCES would be (RESULT-SEQUENCE . SEQUENCES) + for (cl-map-into RESULT-SEQUENCE f . SEQUENCES) + +As a side effect, it checks that ALL-SEQUENCES are of sequence +types. + +Example: +ELISP> (mapcar (lambda (arglist) + (apply #'cl--compute-map-into-signature arglist)) + '(( () () () ) ; signature #b1000 + ( () () [] ) ; signature #b1001 + ( () [] () ) ; signature #b1010 + ( () [] [] ) ; signature #b1011 + ( [] () () ) ; signature #b1100 + )) +(8 9 10 11 12)" + ;; This is not `cl-map-into'-specific and could be used for other caches + ;; which is why we don't specify arglist as (result &rest sequences). + ;; For the time being (while this dispatch is not used widely), + ;; neither docstring nor name reflect this. + (let ((signature 1)) + (dolist (s all-sequences signature) + (setq signature (ash signature 1)) + (cl-etypecase s + (list) + ((or string vector bool-vector) (cl-incf signature)))))) + +(cl-defmacro cl--do-seq-type-signature ((type-var signature &optional result) + &body body) + "With TYPE-VAR bound to a sequence type, evaluate BODY forms, return RESULT. + +TYPE-VAR goes across sequence types in an arglist corresponding +to SIGNATURE that encodes sequence types in that arglist. + +Iteration goes from arglist's end to arglist's start. + +If :first is present at toplevel in BODY, all forms following +it (and those forms only) are evaluated in order when TYPE-VAR is +bound to the first sequence type in the arglist --- which would +be the last sequence type derived from SIGNATURE: see the +previous paragraph. At other iteration steps, only forms +preceding the first :first are evaluated. + +Subsequent instances of toplevel :first in BODY don't affect anything." + (declare (indent 1)) + (let* ((main (cl-copy-list body)) + (first (if (eq :first (car main)) (progn (setf main nil) + (cdr main)) + (cl-loop with sublist = main + while sublist do + (when (eq :first (cadr sublist)) + (setf first (cddr sublist) (cdr sublist) nil) + (cl-return first)) + (pop sublist))))) + (let ((sig (make-symbol "sig"))) + `(let ((,sig ,signature) ,type-var) + ;; (declare (type (integer (1)) ,sig) + ;; ;; Let's keep nil for now. + ;; (type (member nil list vector) ,type-var)) + (cl-check-type ,sig (integer (1))) + (cl-loop (cond + ((or (when (= 2 ,sig) (setq ,type-var 'list)) + (when (= 3 ,sig) (setq ,type-var 'array))) + ;; This duplicates main code sometimes. Maybe, + ;; there is elegant enough way to eliminate duplication. + ,@(or first main) (cl-return ,result)) + (t (setq ,type-var (if (zerop (mod ,sig 2)) + 'list + 'array)) + ,@main)) + (setf ,sig (floor ,sig 2))))))) + +(defun cl--make-map-into-mapper (signature &optional do-not-compile) + "Return mapper for `cl-map-into' specialized on arglists of given SIGNATURE. + +If DO-NOT-COMPILE is nil (default), return byte-compiled function. +Otherwise, return lambda form. + +Example: +ELISP> (cl--make-map-into-mapper #b10101 t) +(lambda (f result-list array-3 list-2 array-1) + (cl-loop for elt in-ref result-list + for elt-3 across array-3 + for elt-2 in list-2 + for elt-1 across array-1 + do (setf elt (funcall f elt-3 elt-2 elt-1)) + finally return result-list))" + (let ((gensym-counter 1) f xs ss loop result-elt result-var) + (cl--do-seq-type-signature (type signature) + (setq loop (nconc (list 'for (let ((it (gensym "elt-"))) + (push it xs) + (cl-decf gensym-counter) + it) + (cl-case type + (list 'in) + (array 'across)) + (let ((it (gensym (format "%s-" type)))) + (push it ss) + it)) + loop)) + :first + (setq loop (nconc (list 'for (setq result-elt (make-symbol "elt")) + (cl-case type + (list 'in-ref) + (array 'across-ref)) + (setq result-var + (make-symbol (format "result-%s" type)))) + loop))) + (funcall + (if do-not-compile #'identity #'byte-compile) + `(lambda ,(cons (setq f (make-symbol "f")) (cons result-var ss)) + (cl-loop ,@(nconc loop `(do (setf ,result-elt (funcall ,f ,@xs)) + ;; Bytecode looks better + ;; with finally return .. + ;; than with finally (cl-return ..). + finally return ,result-var))))))) + +(defun cl-map-into (result-sequence function &rest sequences) + "Map FUNCTION over SEQUENCES, recording values into RESULT-SEQUENCE. + +RESULT-SEQUENCE is destructively modified. + +RESULT-SEQUENCE and each element of SEQUENCES can each be either +a list, a vector, a string, or a bool-vector. If RESULT-SEQUENCE +and each element of SEQUENCES are not all the same length, the +iteration terminates when the shortest sequence (of any of the +SEQUENCES or the RESULT-SEQUENCE) is exhausted. If +RESULT-SEQUENCE is longer than the shortest element of SEQUENCES, +extra elements at the end of RESULT-SEQUENCE are left unchanged. + +Return RESULT-SEQUENCE." + (cl-check-type function function) + (apply + (let* ((sig (apply #'cl--compute-map-into-signature result-sequence + sequences)) + (small (< sig cl--map-into-max-small-signature))) + (with-memoization (if small (aref cl--map-into-mappers-array sig) + ;; TODO: Order alist entries for faster lookup + ;; (note that we'll have to abandon alist-get then). + (alist-get sig cl--map-into-mappers-alist + nil nil #'=)) + (cl--make-map-into-mapper sig))) + function result-sequence sequences)) + + ;;; Control structures. ;;;###autoload diff --git a/test/lisp/emacs-lisp/cl-extra-tests.el b/test/lisp/emacs-lisp/cl-extra-tests.el index 91f0a1e201..a4f21f2edf 100644 --- a/test/lisp/emacs-lisp/cl-extra-tests.el +++ b/test/lisp/emacs-lisp/cl-extra-tests.el @@ -35,6 +35,67 @@ (should (eq (cl-getf plist 'y :none) nil)) (should (eq (cl-getf plist 'z :none) :none)))) +(ert-deftest cl-map-into () + (should (equal '(42 42 42) + (cl-map-into (list 0 0 0) #'+ '(1 2 3) [41 40 39]))) + (should (equal '(42 42 42) + (cl-map-into (list 0 0 0) #'+ [41 40 39] '(1 2 3)))) + (should (equal '(42 42 42) + (cl-map-into (list 0 0 0) #'* '(1 2 3) [42 21 14]))) + (should (equal '(42 42 42) + (let ((s (list 0 0 0))) + (cl-map-into s #'+ '(1 2 3) [41 40 39]) + s))) + (should (equal '(42 42 42) + (let ((s (list 0 0 0))) + (cl-map-into s #'+ s [41 40 39] '(1 2 3)) + s))) + (should (equal '(42 42 42) + (let ((s (list 0 0 0))) + (cl-map-into s #'+ '(1 2 3) s [41 40 39]) + s))) + (should (equal '(42 42 42) + (let ((s (list 0 0 0))) + (cl-map-into s #'+ '(1 2 3) [41 40 39] s) + s))) + (should (equal '(42 42 42) + (let ((s (list 18 19 20))) + (cl-map-into s #'+ s '(6 4 2 1 not-even-a-number) s) + s))) + (should (equal [42 42 42] + (let ((s (vector 0 0 0))) + (cl-map-into s #'+ '(1 2 3) [41 40 39]) + s))) + (should (equal [42 42 42] + (let ((s (vector 0 0 0))) + (cl-map-into s #'+ [41 40 39] '(1 2 3)) + s))) + (should (equal [42 42 42] + (let ((s (vector 18 19 20))) + (cl-map-into s #'+ s '(6 4 2 1 not-even-a-number) s) + s))) + (should (equal "Lisp" + (let ((s (copy-sequence "Loop"))) + (cl-map-into s (lambda (mask new old) (if mask new old)) + (bool-vector nil t t nil) "Disjoint" s) + s))) + (should (equal '(1 2 3) + (let ((s (list 'one 'two 'three))) + (cl-map-into s (let ((n 0)) (lambda () (cl-incf n)))) + s))) + (should (equal (bool-vector t nil t nil t) + (let ((s (bool-vector nil nil nil nil nil))) + (cl-map-into s #'cl-evenp '#1=(0 1 . #1#)) + s))) + (should (equal "GNU GNU GNU GNU" + (let ((cyclically '#1=(t nil . #1#)) + (glue '#1=(?G ?L ?U ?E . #1#)) + (ants '#1=(?A ?N ?T ?\s . #1#)) + (s (make-string 15 0))) + (cl-map-into s (lambda (x y z) (if x y z)) + cyclically glue ants) + s)))) + (ert-deftest cl-extra-test-mapc () (let ((lst '(a b c)) (lst2 '(d e f)) -- 2.32.0