;;; pcase.el --- ML-style pattern-matching macro for Elisp -*- lexical-binding: t; coding: utf-8 -*-
-;; Copyright (C) 2010-2012 Free Software Foundation, Inc.
+;; Copyright (C) 2010-2014 Free Software Foundation, Inc.
;; Author: Stefan Monnier <monnier@iro.umontreal.ca>
;; Keywords:
;; is in a loop, the repeated macro-expansion becomes terribly costly, so we
;; memoize previous macro expansions to try and avoid recomputing them
;; over and over again.
+;; FIXME: Now that macroexpansion is also performed when loading an interpreted
+;; file, this is not a real problem any more.
(defconst pcase--memoize (make-hash-table :weakness 'key :test 'eq))
-
-(defconst pcase--dontcare-upats '(t _ dontcare))
+;; (defconst pcase--memoize-1 (make-hash-table :test 'eq))
+;; (defconst pcase--memoize-2 (make-hash-table :weakness 'key :test 'equal))
+
+(defconst pcase--dontcare-upats '(t _ pcase--dontcare))
+
+(def-edebug-spec
+ pcase-UPAT
+ (&or symbolp
+ ("or" &rest pcase-UPAT)
+ ("and" &rest pcase-UPAT)
+ ("`" pcase-QPAT)
+ ("guard" form)
+ ("let" pcase-UPAT form)
+ ("pred"
+ &or lambda-expr
+ ;; Punt on macros/special forms.
+ (functionp &rest form)
+ sexp)
+ sexp))
+
+(def-edebug-spec
+ pcase-QPAT
+ (&or ("," pcase-UPAT)
+ (pcase-QPAT . pcase-QPAT)
+ sexp))
;;;###autoload
(defmacro pcase (exp &rest cases)
UPatterns can take the following forms:
_ matches anything.
+ SELFQUOTING matches itself. This includes keywords, numbers, and strings.
SYMBOL matches anything and binds it to SYMBOL.
(or UPAT...) matches if any of the patterns matches.
(and UPAT...) matches if all the patterns match.
PRED can take the form
FUNCTION in which case it gets called with one argument.
- (FUN ARG1 .. ARGN) in which case it gets called with N+1 arguments.
+ (FUN ARG1 .. ARGN) in which case it gets called with an N+1'th argument
+ which is the value being matched.
A PRED of the form FUNCTION is equivalent to one of the form (FUNCTION).
PRED patterns can refer to variables bound earlier in the pattern.
E.g. you can match pairs where the cdr is larger than the car with a pattern
like `(,a . ,(pred (< a))) or, with more checks:
`(,(and a (pred numberp)) . ,(and (pred numberp) (pred (< a))))"
- (declare (indent 1) (debug cl-case)) ;FIXME: edebug `guard' and vars.
+ (declare (indent 1) (debug (form &rest (pcase-UPAT body))))
;; We want to use a weak hash table as a cache, but the key will unavoidably
;; be based on `exp' and `cases', yet `cases' is a fresh new list each time
;; we're called so it'll be immediately GC'd. So we use (car cases) as key
(if (and (equal exp (car data)) (equal cases (cadr data)))
;; We have the right expansion.
(cddr data)
+ ;; (when (gethash (car cases) pcase--memoize-1)
+ ;; (message "pcase-memoize failed because of weak key!!"))
+ ;; (when (gethash (car cases) pcase--memoize-2)
+ ;; (message "pcase-memoize failed because of eq test on %S"
+ ;; (car cases)))
(when data
(message "pcase-memoize: equal first branch, yet different"))
(let ((expansion (pcase--expand exp cases)))
- (puthash (car cases) (cons exp (cons cases expansion)) pcase--memoize)
+ (puthash (car cases) `(,exp ,cases ,@expansion) pcase--memoize)
+ ;; (puthash (car cases) `(,exp ,cases ,@expansion) pcase--memoize-1)
+ ;; (puthash (car cases) `(,exp ,cases ,@expansion) pcase--memoize-2)
expansion))))
+(defun pcase--let* (bindings body)
+ (cond
+ ((null bindings) (macroexp-progn body))
+ ((pcase--trivial-upat-p (caar bindings))
+ (macroexp-let* `(,(car bindings)) (pcase--let* (cdr bindings) body)))
+ (t
+ (let ((binding (pop bindings)))
+ (pcase--expand
+ (cadr binding)
+ `((,(car binding) ,(pcase--let* bindings body))
+ ;; We can either signal an error here, or just use `pcase--dontcare'
+ ;; which generates more efficient code. In practice, if we use
+ ;; `pcase--dontcare' we will still often get an error and the few
+ ;; cases where we don't do not matter that much, so
+ ;; it's a better choice.
+ (pcase--dontcare nil)))))))
+
;;;###autoload
(defmacro pcase-let* (bindings &rest body)
"Like `let*' but where you can use `pcase' patterns for bindings.
BODY should be an expression, and BINDINGS should be a list of bindings
of the form (UPAT EXP)."
(declare (indent 1)
- (debug ((&rest &or (sexp &optional form) symbolp) body)))
- (cond
- ((null bindings) (if (> (length body) 1) `(progn ,@body) (car body)))
- ((pcase--trivial-upat-p (caar bindings))
- `(let (,(car bindings)) (pcase-let* ,(cdr bindings) ,@body)))
- (t
- `(pcase ,(cadr (car bindings))
- (,(caar bindings) (pcase-let* ,(cdr bindings) ,@body))
- ;; We can either signal an error here, or just use `dontcare' which
- ;; generates more efficient code. In practice, if we use `dontcare' we
- ;; will still often get an error and the few cases where we don't do not
- ;; matter that much, so it's a better choice.
- (dontcare nil)))))
+ (debug ((&rest (pcase-UPAT &optional form)) body)))
+ (let ((cached (gethash bindings pcase--memoize)))
+ ;; cached = (BODY . EXPANSION)
+ (if (equal (car cached) body)
+ (cdr cached)
+ (let ((expansion (pcase--let* bindings body)))
+ (puthash bindings (cons body expansion) pcase--memoize)
+ expansion))))
;;;###autoload
(defmacro pcase-let (bindings &rest body)
`(let ,(nreverse bindings) (pcase-let* ,matches ,@body)))))
(defmacro pcase-dolist (spec &rest body)
- (declare (indent 1))
+ (declare (indent 1) (debug ((pcase-UPAT form) body)))
(if (pcase--trivial-upat-p (car spec))
`(dolist ,spec ,@body)
(let ((tmpvar (make-symbol "x")))
(defun pcase--expand (exp cases)
;; (message "pid=%S (pcase--expand %S ...hash=%S)"
;; (emacs-pid) exp (sxhash cases))
- (let* ((defs (if (symbolp exp) '()
- (let ((sym (make-symbol "x")))
- (prog1 `((,sym ,exp)) (setq exp sym)))))
- (seen '())
- (codegen
- (lambda (code vars)
- (let ((prev (assq code seen)))
- (if (not prev)
- (let ((res (pcase-codegen code vars)))
- (push (list code vars res) seen)
- res)
- ;; Since we use a tree-based pattern matching
- ;; technique, the leaves (the places that contain the
- ;; code to run once a pattern is matched) can get
- ;; copied a very large number of times, so to avoid
- ;; code explosion, we need to keep track of how many
- ;; times we've used each leaf and move it
- ;; to a separate function if that number is too high.
- ;;
- ;; We've already used this branch. So it is shared.
- (let* ((code (car prev)) (cdrprev (cdr prev))
- (prevvars (car cdrprev)) (cddrprev (cdr cdrprev))
- (res (car cddrprev)))
- (unless (symbolp res)
- ;; This is the first repeat, so we have to move
- ;; the branch to a separate function.
- (let ((bsym
- (make-symbol (format "pcase-%d" (length defs)))))
- (push `(,bsym (lambda ,(mapcar #'car prevvars) ,@code)) defs)
- (setcar res 'funcall)
- (setcdr res (cons bsym (mapcar #'cdr prevvars)))
- (setcar (cddr prev) bsym)
- (setq res bsym)))
- (setq vars (copy-sequence vars))
- (let ((args (mapcar (lambda (pa)
- (let ((v (assq (car pa) vars)))
- (setq vars (delq v vars))
- (cdr v)))
- prevvars)))
- ;; If some of `vars' were not found in `prevvars', that's
- ;; OK it just means those vars aren't present in all
- ;; branches, so they can be used within the pattern
- ;; (e.g. by a `guard/let/pred') but not in the branch.
- ;; FIXME: But if some of `prevvars' are not in `vars' we
- ;; should remove them from `prevvars'!
- `(funcall ,res ,@args)))))))
- (main
- (pcase--u
- (mapcar (lambda (case)
- `((match ,exp . ,(car case))
- ,(apply-partially
- (if (pcase--small-branch-p (cdr case))
- ;; Don't bother sharing multiple
- ;; occurrences of this leaf since it's small.
- #'pcase-codegen codegen)
- (cdr case))))
- cases))))
- (if (null defs) main
+ (macroexp-let2 macroexp-copyable-p val exp
+ (let* ((defs ())
+ (seen '())
+ (codegen
+ (lambda (code vars)
+ (let ((prev (assq code seen)))
+ (if (not prev)
+ (let ((res (pcase-codegen code vars)))
+ (push (list code vars res) seen)
+ res)
+ ;; Since we use a tree-based pattern matching
+ ;; technique, the leaves (the places that contain the
+ ;; code to run once a pattern is matched) can get
+ ;; copied a very large number of times, so to avoid
+ ;; code explosion, we need to keep track of how many
+ ;; times we've used each leaf and move it
+ ;; to a separate function if that number is too high.
+ ;;
+ ;; We've already used this branch. So it is shared.
+ (let* ((code (car prev)) (cdrprev (cdr prev))
+ (prevvars (car cdrprev)) (cddrprev (cdr cdrprev))
+ (res (car cddrprev)))
+ (unless (symbolp res)
+ ;; This is the first repeat, so we have to move
+ ;; the branch to a separate function.
+ (let ((bsym
+ (make-symbol (format "pcase-%d" (length defs)))))
+ (push `(,bsym (lambda ,(mapcar #'car prevvars) ,@code))
+ defs)
+ (setcar res 'funcall)
+ (setcdr res (cons bsym (mapcar #'cdr prevvars)))
+ (setcar (cddr prev) bsym)
+ (setq res bsym)))
+ (setq vars (copy-sequence vars))
+ (let ((args (mapcar (lambda (pa)
+ (let ((v (assq (car pa) vars)))
+ (setq vars (delq v vars))
+ (cdr v)))
+ prevvars)))
+ ;; If some of `vars' were not found in `prevvars', that's
+ ;; OK it just means those vars aren't present in all
+ ;; branches, so they can be used within the pattern
+ ;; (e.g. by a `guard/let/pred') but not in the branch.
+ ;; FIXME: But if some of `prevvars' are not in `vars' we
+ ;; should remove them from `prevvars'!
+ `(funcall ,res ,@args)))))))
+ (used-cases ())
+ (main
+ (pcase--u
+ (mapcar (lambda (case)
+ `((match ,val . ,(car case))
+ ,(lambda (vars)
+ (unless (memq case used-cases)
+ ;; Keep track of the cases that are used.
+ (push case used-cases))
+ (funcall
+ (if (pcase--small-branch-p (cdr case))
+ ;; Don't bother sharing multiple
+ ;; occurrences of this leaf since it's small.
+ #'pcase-codegen codegen)
+ (cdr case)
+ vars))))
+ cases))))
+ (dolist (case cases)
+ (unless (or (memq case used-cases) (eq (car case) 'pcase--dontcare))
+ (message "Redundant pcase pattern: %S" (car case))))
(macroexp-let* defs main))))
(defun pcase-codegen (code vars)
(symbolp . numberp)
(symbolp . consp)
(symbolp . arrayp)
+ (symbolp . vectorp)
(symbolp . stringp)
(symbolp . byte-code-function-p)
(integerp . consp)
(integerp . arrayp)
+ (integerp . vectorp)
(integerp . stringp)
(integerp . byte-code-function-p)
(numberp . consp)
(numberp . arrayp)
+ (numberp . vectorp)
(numberp . stringp)
(numberp . byte-code-function-p)
(consp . arrayp)
+ (consp . vectorp)
(consp . stringp)
(consp . byte-code-function-p)
- (arrayp . stringp)
(arrayp . byte-code-function-p)
+ (vectorp . byte-code-function-p)
+ (stringp . vectorp)
(stringp . byte-code-function-p)))
+(defun pcase--mutually-exclusive-p (pred1 pred2)
+ (or (member (cons pred1 pred2)
+ pcase-mutually-exclusive-predicates)
+ (member (cons pred2 pred1)
+ pcase-mutually-exclusive-predicates)))
+
(defun pcase--split-match (sym splitter match)
(cond
((eq (car match) 'match)
(match ,symd . ,(pcase--upat (cdr qpat))))
:pcase--fail)))
;; A QPattern but not for a cons, can only go to the `else' side.
- ((eq (car-safe pat) '\`) (cons :pcase--fail nil))
+ ((eq (car-safe pat) '\`) '(:pcase--fail . nil))
((and (eq (car-safe pat) 'pred)
- (or (member (cons 'consp (cadr pat))
- pcase-mutually-exclusive-predicates)
- (member (cons (cadr pat) 'consp)
- pcase-mutually-exclusive-predicates)))
- (cons :pcase--fail nil))))
+ (pcase--mutually-exclusive-p #'consp (cadr pat)))
+ '(:pcase--fail . nil))))
(defun pcase--split-equal (elem pat)
(cond
;; The same match will give the same result.
((and (eq (car-safe pat) '\`) (equal (cadr pat) elem))
- (cons :pcase--succeed :pcase--fail))
+ '(:pcase--succeed . :pcase--fail))
;; A different match will fail if this one succeeds.
((and (eq (car-safe pat) '\`)
;; (or (integerp (cadr pat)) (symbolp (cadr pat))
;; (consp (cadr pat)))
)
- (cons :pcase--fail nil))
+ '(:pcase--fail . nil))
((and (eq (car-safe pat) 'pred)
(symbolp (cadr pat))
- (get (cadr pat) 'side-effect-free)
- (funcall (cadr pat) elem))
- (cons :pcase--succeed nil))))
+ (get (cadr pat) 'side-effect-free))
+ (ignore-errors
+ (if (funcall (cadr pat) elem)
+ '(:pcase--succeed . nil)
+ '(:pcase--fail . nil))))))
(defun pcase--split-member (elems pat)
;; Based on pcase--split-equal.
;; The same match (or a match of membership in a superset) will
;; give the same result, but we don't know how to check it.
;; (???
- ;; (cons :pcase--succeed nil))
+ ;; '(:pcase--succeed . nil))
;; A match for one of the elements may succeed or fail.
((and (eq (car-safe pat) '\`) (member (cadr pat) elems))
nil)
;; (or (integerp (cadr pat)) (symbolp (cadr pat))
;; (consp (cadr pat)))
)
- (cons :pcase--fail nil))
+ '(:pcase--fail . nil))
((and (eq (car-safe pat) 'pred)
(symbolp (cadr pat))
(get (cadr pat) 'side-effect-free)
- (let ((p (cadr pat)) (all t))
- (dolist (elem elems)
- (unless (funcall p elem) (setq all nil)))
- all))
- (cons :pcase--succeed nil))))
-
-(defun pcase--split-pred (upat pat)
- ;; FIXME: For predicates like (pred (> a)), two such predicates may
- ;; actually refer to different variables `a'.
+ (ignore-errors
+ (let ((p (cadr pat)) (all t))
+ (dolist (elem elems)
+ (unless (funcall p elem) (setq all nil)))
+ all)))
+ '(:pcase--succeed . nil))))
+
+(defun pcase--split-pred (vars upat pat)
(let (test)
(cond
- ((equal upat pat) (cons :pcase--succeed :pcase--fail))
+ ((and (equal upat pat)
+ ;; For predicates like (pred (> a)), two such predicates may
+ ;; actually refer to different variables `a'.
+ (or (and (eq 'pred (car upat)) (symbolp (cadr upat)))
+ ;; FIXME: `vars' gives us the environment in which `upat' will
+ ;; run, but we don't have the environment in which `pat' will
+ ;; run, so we can't do a reliable verification. But let's try
+ ;; and catch at least the easy cases such as (bug#14773).
+ (not (pcase--fgrep (mapcar #'car vars) (cadr upat)))))
+ '(:pcase--succeed . :pcase--fail))
((and (eq 'pred (car upat))
- (eq 'pred (car-safe pat))
- (or (member (cons (cadr upat) (cadr pat))
- pcase-mutually-exclusive-predicates)
- (member (cons (cadr pat) (cadr upat))
- pcase-mutually-exclusive-predicates)))
- (cons :pcase--fail nil))
+ (let ((otherpred
+ (cond ((eq 'pred (car-safe pat)) (cadr pat))
+ ((not (eq '\` (car-safe pat))) nil)
+ ((consp (cadr pat)) #'consp)
+ ((vectorp (cadr pat)) #'vectorp)
+ ((byte-code-function-p (cadr pat))
+ #'byte-code-function-p))))
+ (pcase--mutually-exclusive-p (cadr upat) otherpred)))
+ '(:pcase--fail . nil))
((and (eq 'pred (car upat))
(eq '\` (car-safe pat))
(symbolp (cadr upat))
(ignore-errors
(setq test (list (funcall (cadr upat) (cadr pat))))))
(if (car test)
- (cons nil :pcase--fail)
- (cons :pcase--fail nil))))))
+ '(nil . :pcase--fail)
+ '(:pcase--fail . nil))))))
(defun pcase--fgrep (vars sexp)
"Check which of the symbols VARS appear in SEXP."
(and (memq sexp vars) (not (memq sexp res)) (push sexp res))
res))
+(defun pcase--self-quoting-p (upat)
+ (or (keywordp upat) (numberp upat) (stringp upat)))
+
+(defsubst pcase--mark-used (sym)
+ ;; Exceptionally, `sym' may be a constant expression rather than a symbol.
+ (if (symbolp sym) (put sym 'pcase-used t)))
+
;; It's very tempting to use `pcase' below, tho obviously, it'd create
;; bootstrapping problems.
(defun pcase--u1 (matches code vars rest)
(upat (cdr cdrpopmatches)))
(cond
((memq upat '(t _)) (pcase--u1 matches code vars rest))
- ((eq upat 'dontcare) :pcase--dontcare)
+ ((eq upat 'pcase--dontcare) :pcase--dontcare)
((memq (car-safe upat) '(guard pred))
- (if (eq (car upat) 'pred) (put sym 'pcase-used t))
+ (if (eq (car upat) 'pred) (pcase--mark-used sym))
(let* ((splitrest
(pcase--split-rest
- sym (apply-partially #'pcase--split-pred upat) rest))
+ sym (lambda (pat) (pcase--split-pred vars upat pat)) rest))
(then-rest (car splitrest))
(else-rest (cdr splitrest)))
(pcase--if (if (and (eq (car upat) 'pred) (symbolp (cadr upat)))
`(let* ,env ,call))))
(pcase--u1 matches code vars then-rest)
(pcase--u else-rest))))
+ ((pcase--self-quoting-p upat)
+ (pcase--mark-used sym)
+ (pcase--q1 sym upat matches code vars rest))
((symbolp upat)
- (put sym 'pcase-used t)
+ (pcase--mark-used sym)
(if (not (assq upat vars))
(pcase--u1 matches code (cons (cons upat sym) vars) rest)
;; Non-linear pattern. Turn it into an `eq' test.
;; A upat of the form (let VAR EXP).
;; (pcase--u1 matches code
;; (cons (cons (nth 1 upat) (nth 2 upat)) vars) rest)
- (macroexp-let²
+ (macroexp-let2
macroexp-copyable-p sym
(let* ((exp (nth 2 upat))
(found (assq exp vars)))
(pcase--u1 (cons `(match ,sym . ,(nth 1 upat)) matches)
code vars rest)))
((eq (car-safe upat) '\`)
- (put sym 'pcase-used t)
+ (pcase--mark-used sym)
(pcase--q1 sym (cadr upat) matches code vars rest))
((eq (car-safe upat) 'or)
(let ((all (> (length (cdr upat)) 1))
(memq-fine t))
(when all
(dolist (alt (cdr upat))
- (unless (and (eq (car-safe alt) '\`)
- (or (symbolp (cadr alt)) (integerp (cadr alt))
- (setq memq-fine nil)
- (stringp (cadr alt))))
+ (unless (if (pcase--self-quoting-p alt)
+ (progn
+ (unless (or (symbolp alt) (integerp alt))
+ (setq memq-fine nil))
+ t)
+ (and (eq (car-safe alt) '\`)
+ (or (symbolp (cadr alt)) (integerp (cadr alt))
+ (setq memq-fine nil)
+ (stringp (cadr alt)))))
(setq all nil))))
(if all
;; Use memq for (or `a `b `c `d) rather than a big tree.
- (let* ((elems (mapcar 'cadr (cdr upat)))
+ (let* ((elems (mapcar (lambda (x) (if (consp x) (cadr x) x))
+ (cdr upat)))
(splitrest
(pcase--split-rest
- sym (apply-partially #'pcase--split-member elems) rest))
+ sym (lambda (pat) (pcase--split-member elems pat)) rest))
(then-rest (car splitrest))
(else-rest (cdr splitrest)))
- (put sym 'pcase-used t)
+ (pcase--mark-used sym)
(pcase--if `(,(if memq-fine #'memq #'member) ,sym ',elems)
(pcase--u1 matches code vars then-rest)
(pcase--u else-rest)))
(symd (make-symbol "xcdr"))
(splitrest (pcase--split-rest
sym
- (apply-partially #'pcase--split-consp syma symd)
+ (lambda (pat) (pcase--split-consp syma symd pat))
rest))
(then-rest (car splitrest))
(else-rest (cdr splitrest))
;; `then-body', but only within some sub-branch).
(macroexp-let*
`(,@(if (get syma 'pcase-used) `((,syma (car ,sym))))
- ,@(if (get symd 'pcase-used) `((,symd (cdr ,sym)))))
+ ,@(if (get symd 'pcase-used) `((,symd (cdr ,sym)))))
then-body)
(pcase--u else-rest))))
((or (integerp qpat) (symbolp qpat) (stringp qpat))
- (let* ((splitrest (pcase--split-rest
- sym (apply-partially 'pcase--split-equal qpat) rest))
- (then-rest (car splitrest))
- (else-rest (cdr splitrest)))
+ (let* ((splitrest (pcase--split-rest
+ sym (lambda (pat) (pcase--split-equal qpat pat)) rest))
+ (then-rest (car splitrest))
+ (else-rest (cdr splitrest)))
(pcase--if (cond
((stringp qpat) `(equal ,sym ,qpat))
((null qpat) `(null ,sym))
HCoop / bpt / emacs.git / blobdiff