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|
(defvar *match-form*)
(defstruct match-guard ()
temps
vars
var-exprs
pure-temps
pure-temp-exprs
(guard-expr t)
(test-expr t)
(:method assignments (me)
(mapcar (ret ^(set ,@1 ,@2)) me.vars me.var-exprs))
(:method lets (me)
(mapcar (ret ^(,@1 ,@2)) me.pure-temps me.pure-temp-exprs)))
(defstruct guard-disjunction ()
guard-chains
sub-patterns
all-vars)
(defstruct compiled-match ()
pattern
obj-var
guard-chain
(:method get-vars (me)
(uniq (get-vars me.guard-chain)))
(:method wrap-guards (me . forms)
(labels ((wrg (rgc exp)
(each ((g rgc))
(typecase g
(match-guard
(let ((lets g.(lets))
(temps g.temps))
(if (neq t g.test-expr)
(set exp ^(if ,g.test-expr ,exp)))
(cond
((and lets temps)
(set exp ^(alet ,lets
(let ,temps
,*g.(assignments)
,exp))))
(lets
(set exp ^(alet ,lets
,*g.(assignments)
,exp)))
(temps
(set exp ^(let ,temps
,*g.(assignments)
,exp)))
(t
(set exp ^(progn ,*g.(assignments)
,exp))))
(when (neq t g.guard-expr)
(set exp ^(if ,g.guard-expr ,exp)))))
(guard-disjunction
(let* ((vars [mapcar get-vars g.guard-chains])
(back-vars (cons nil
(reverse
[mapcar (ap append)
(conses (reverse vars))])))
(branches (collect-each ((gc g.guard-chains)
(v vars)
(bv back-vars))
^(progn
(set ,*(mappend (ret ^(,@1 nil))
(diff bv v)))
,(wrg (reverse gc) t)))))
(set exp ^(when (or ,*branches)
,exp))))
(t (compile-error *match-form*
"internal error: bad guard ~s" g))))
exp))
(wrg (reverse me.guard-chain)
^(progn ,*forms))))
(:method add-guard-pre (me guard)
(push guard me.guard-chain))
(:method add-guards-pre (me . guards)
(set me.guard-chain
(append guards
me.guard-chain)))
(:method add-guards-post (me . guards)
(set me.guard-chain
(append me.guard-chain
guards))))
(defstruct var-list ()
vars
menv
(:method exists (me sym) (or (member sym me.vars)
(lexical-var-p me.menv sym)
(boundp sym)))
(:method record (me sym) (push sym me.vars))
(:method merge (me copy) (each ((v copy.vars)) (pushnew v me.vars))))
(defun get-vars (guard-chain)
(append-each ((g guard-chain))
(typecase g
(match-guard
g.vars)
(guard-disjunction
(append-each ((gc g.guard-chains)) (get-vars gc)))
(t (compile-error *match-form*
"internal error: bad guard ~s" g)))))
(defun compile-struct-match (struct-pat obj-var var-list)
(mac-param-bind *match-form* (op required-type . pairs) struct-pat
(let* ((loose-p (not (bindable required-type)))
(slot-pairs (plist-to-alist pairs))
(required-slots [mapcar car slot-pairs])
(slot-gensyms [mapcar gensym required-slots])
(type-gensym (if loose-p
(gensym "type-")))
(slot-patterns [mapcar cdr slot-pairs])
(slot-matches [mapcar (lop compile-match var-list)
slot-patterns slot-gensyms])
(type-match (if loose-p
(compile-match required-type type-gensym var-list)))
(slot-val-exprs [mapcar (ret ^(slot ,obj-var ',@1)) required-slots])
(guard0 (if loose-p
(list (new match-guard
pure-temps (list type-gensym)
pure-temp-exprs (list ^(struct-type ,obj-var))
guard-expr ^(structp ,obj-var)))))
(guard1 (list (new match-guard
pure-temps slot-gensyms
pure-temp-exprs slot-val-exprs
guard-expr (if loose-p
^(and ,*(mapcar
(ret ^(slotp ,type-gensym
',@1))
required-slots))
^(subtypep (typeof ,obj-var)
',required-type))))))
(unless loose-p
(let ((type (find-struct-type required-type)))
(if type
(each ((slot required-slots))
(unless (slotp type slot)
(compile-defr-warning *match-form* ^(slot . ,slot)
"~s has no slot ~s"
required-type slot)))
(compile-defr-warning *match-form* ^(struct-type . ,required-type)
"no such struct type: ~s"
required-type))))
(new compiled-match
pattern struct-pat
obj-var obj-var
guard-chain (append guard0
type-match.?guard-chain
guard1
(mappend .guard-chain slot-matches))))))
(defun compile-var-match (sym obj-var var-list)
(cond
((null sym)
(new compiled-match
obj-var obj-var))
((not (bindable sym))
(compile-error *match-form* "~s is not a bindable symbol" sym))
((not var-list.(exists sym))
var-list.(record sym)
(new compiled-match
pattern sym
obj-var obj-var
guard-chain (if sym (list (new match-guard
vars (list sym)
var-exprs (list obj-var))))))
(t (new compiled-match
pattern sym
obj-var obj-var
guard-chain (list (new match-guard
guard-expr ^(equal ,obj-var ,sym)))))))
(defun compile-new-var-match (sym obj-var var-list)
(cond
((null sym)
(new compiled-match
obj-var obj-var))
((not (bindable sym))
(compile-error *match-form* "~s is not a bindable symbol" sym))
(t var-list.(record sym)
(new compiled-match
pattern sym
obj-var obj-var
guard-chain (if sym (list (new match-guard
vars (list sym)
var-exprs (list obj-var))))))))
(defun compile-vec-match (vec-pat obj-var var-list)
(let* ((elem-gensyms (mapcar (op gensym `elem-@1-`) (range* 0 (len vec-pat))))
(elem-exprs (mapcar (ret ^[,obj-var ,@1]) (range* 0 (len vec-pat))))
(elem-matches (list-vec [mapcar (lop compile-match var-list)
vec-pat elem-gensyms]))
(pruned-triple (multi (op keep-if .guard-chain @1 third)
elem-gensyms
elem-exprs
elem-matches))
(guard (new match-guard
pure-temps (first pruned-triple)
pure-temp-exprs (second pruned-triple)
guard-expr ^(and (vectorp ,obj-var)
(eql (len ,obj-var) ,(len vec-pat))))))
(new compiled-match
pattern vec-pat
obj-var obj-var
guard-chain (cons guard (mappend .guard-chain elem-matches)))))
(defun compile-range-match (rcons-expr obj-var var-list)
(let ((from (from rcons-expr))
(to (to rcons-expr)))
(let* ((from-match (compile-match from (gensym "from") var-list))
(to-match (compile-match to (gensym "to") var-list))
(guard (new match-guard
guard-expr ^(rangep ,obj-var)
pure-temps (list from-match.obj-var to-match.obj-var)
pure-temp-exprs (list ^(from ,obj-var) ^(to ,obj-var)))))
(new compiled-match
pattern rcons-expr
obj-var obj-var
guard-chain (cons guard (append from-match.guard-chain
to-match.guard-chain))))))
(defun compile-atom-match (atom obj-var var-list)
(flet ((compile-as-atom ()
(new compiled-match
pattern atom
obj-var obj-var
guard-chain (list (new match-guard
guard-expr ^(equal ,obj-var ',atom))))))
(typecase atom
(vec (if (non-triv-pat-p atom)
(compile-vec-match atom obj-var var-list)
(compile-as-atom)))
(range (if (non-triv-pat-p atom)
(compile-range-match atom obj-var var-list)
(compile-as-atom)))
(t (compile-as-atom)))))
(defun compile-op-match (op-expr obj-var var-list)
(let ((var-match (compile-var-match nil obj-var var-list)))
var-match.(add-guard-pre (new match-guard
guard-expr ^ [,op-expr ,obj-var]))
var-match))
(defun compile-predicate-match (exp obj-var var-list)
(let ((head (car exp)))
(if (and (consp head) (eq (car head) 'sys:var))
(tree-case exp
(((sv rvar) (op . args))
(let* ((avar
(condlet
(((vm (member-if [andf consp (op eq (car @1) 'sys:var)]
args)))
(let ((sym (cadar vm)))
(set args (append (ldiff args vm)
(list sym)
(cdr vm)))
sym))
(((vm (memq 'sys:var args)))
(let ((sym (cadr vm)))
(set args (append (ldiff args vm) sym))
sym))))
(res-var (if rvar rvar (gensym "res-")))
(arg-var (if avar avar (gensym "obj-"))))
(unless avar
(set args (append args (list arg-var))))
(let* ((guard (new match-guard
pure-temps (list res-var)
pure-temp-exprs ^((alet ((,arg-var ,obj-var))
(,op ,*args)))
test-expr res-var))
(avar-match (compile-var-match avar obj-var var-list))
(rvar-match (compile-var-match rvar res-var var-list)))
(new compiled-match
pattern exp
obj-var obj-var
guard-chain (append avar-match.guard-chain
(list guard)
rvar-match.guard-chain)))))
(els (compile-error *match-form* "invalid predicate syntax: ~s" exp)))
(compile-predicate-match (list '@nil exp) obj-var var-list))))
(defun compile-cons-structure (cons-pat obj-var var-list)
(mac-param-bind *match-form* (car . cdr) cons-pat
(let* ((car-gensym (gensym))
(cdr-gensym (gensym))
(car-match (compile-match car car-gensym var-list))
(cdr-match (if (consp cdr)
(caseq (car cdr)
((sys:expr sys:var) (compile-match cdr cdr-gensym
var-list))
(t (compile-cons-structure cdr cdr-gensym var-list)))
(compile-atom-match cdr cdr-gensym var-list)))
(guard (new match-guard
pure-temps (append (if car-match.guard-chain
(list car-gensym))
(if cdr-match.guard-chain
(list cdr-gensym)))
pure-temp-exprs (append (if car-match.guard-chain
^((car ,obj-var)))
(if cdr-match.guard-chain
^((cdr ,obj-var))))
guard-expr ^(consp ,obj-var))))
(new compiled-match
pattern cons-pat
obj-var obj-var
guard-chain (cons guard (append car-match.guard-chain
cdr-match.guard-chain))))))
(defun compile-require-match (exp obj-var var-list)
(mac-param-bind *match-form* (op match . conditions) exp
(let ((match (compile-match match obj-var var-list)))
match.(add-guards-post (new match-guard
guard-expr ^(and ,*conditions)))
match)))
(defun compile-as-match (exp obj-var var-list)
(mac-param-bind *match-form* (op sym pat) exp
(let ((var-match (compile-new-var-match sym obj-var var-list))
(pat-match (compile-match pat obj-var var-list)))
(new compiled-match
pattern exp
obj-var obj-var
guard-chain (append var-match.guard-chain
pat-match.guard-chain)))))
(defun compile-with-match (exp obj-var var-list)
(tree-case exp
((op main-pat side-pat-var side-expr)
(let* ((side-var (gensym))
(side-pat (if (or (null side-pat-var) (bindable side-pat-var))
^(sys:var ,side-pat-var)
side-pat-var))
(main-match (compile-match main-pat obj-var var-list))
(side-match (compile-match side-pat side-var var-list))
(guard (new match-guard
pure-temps (list side-var)
pure-temp-exprs (list side-expr))))
(new compiled-match
pattern exp
obj-var obj-var
guard-chain (append main-match.guard-chain
(list guard)
side-match.guard-chain))))
((op side-pat-var side-expr)
(compile-with-match ^(,op @nil ,side-pat-var ,side-expr) obj-var var-list))
(x (compile-error *match-form* "bad syntax: ~s" exp))))
(defun compile-loop-match (exp obj-var var-list)
(mac-param-bind *match-form* (op match) exp
(let* ((no-vac-p (memq op '(coll usr:all*)))
(some-p (eq op 'some))
(coll-p (eq op 'coll))
(item-var (gensym "item-"))
(in-vars var-list.vars)
(cm (compile-match match item-var var-list))
(loop-success-p-var (gensym "loop-success-p-"))
(loop-continue-p-var (gensym "loop-terminate-p"))
(loop-iterated-var (if no-vac-p (gensym "loop-iterated-p")))
(matched-p-var (gensym "matched-p-"))
(iter-var (gensym "iter-"))
(cm-vars cm.(get-vars))
(collect-vars (diff cm-vars in-vars))
(collect-gens [mapcar gensym collect-vars])
(loop ^(for ((,iter-var (iter-begin ,obj-var))
(,loop-continue-p-var t)
,*(if no-vac-p ^((,loop-iterated-var nil))))
((and ,loop-continue-p-var (iter-more ,iter-var))
,(cond
(some-p ^(not ,loop-continue-p-var))
(no-vac-p ^(and ,loop-iterated-var
,loop-continue-p-var))
(t loop-continue-p-var)))
((set ,iter-var (iter-step ,iter-var)))
(let ((,cm.obj-var (iter-item ,iter-var))
,matched-p-var
,*(unless some-p cm-vars))
,cm.(wrap-guards
^(progn
(set ,matched-p-var t)
,*(if no-vac-p
^((set ,loop-iterated-var t)))
,*(unless some-p
(mapcar (ret ^(push ,@1 ,@2))
collect-vars
collect-gens))))
,(unless coll-p ^(,(if some-p 'when 'unless)
,matched-p-var
(set ,loop-continue-p-var nil))))))
(guard0 (new match-guard
vars cm-vars
temps (unless some-p collect-gens)
guard-expr ^(seqp ,obj-var)))
(guard1 (new match-guard
vars (list loop-success-p-var)
var-exprs (list loop)
test-expr (if some-p
loop-success-p-var
^(when ,loop-success-p-var
,*(mapcar (ret ^(set ,@1 (nreverse ,@2)))
collect-vars collect-gens)
t)))))
(new compiled-match
pattern exp
obj-var obj-var
guard-chain (list guard0 guard1)))))
(defun compile-or-match (par-pat obj-var var-list)
(mac-param-bind *match-form* (op . pats) par-pat
(let* ((var-lists (mapcar (ret (copy var-list)) pats))
(par-matches (mapcar (op compile-match @1 obj-var @2)
pats var-lists))
(dj-guard (new guard-disjunction
guard-chains (mapcar .guard-chain par-matches)
sub-patterns par-matches)))
(each ((vl var-lists))
var-list.(merge vl))
(new compiled-match
pattern par-pat
obj-var obj-var
guard-chain (list dj-guard)))))
(defun compile-and-match (and-pat obj-var var-list)
(mac-param-bind *match-form* (op . pats) and-pat
(let* ((par-matches (mapcar (lop compile-match obj-var var-list) pats)))
(new compiled-match
pattern and-pat
obj-var obj-var
guard-chain (mappend .guard-chain par-matches)))))
(defun compile-not-match (pattern obj-var var-list)
(mac-param-bind *match-form* (op pattern) pattern
(let* ((pm (compile-match pattern obj-var var-list))
(guard (new match-guard
guard-expr ^(not (let ,pm.(get-vars)
,pm.(wrap-guards t))))))
(new compiled-match
pattern pattern
obj-var obj-var
guard-chain (list guard)))))
(defun compile-hash-match (hash-expr obj-var var-list)
(tree-bind (op . pairs) hash-expr
(let* ((hash-alist-var (gensym "hash-alist-"))
(hash-alt-val ^',(gensym "alt"))
(need-alist-p nil)
(hash-matches
(collect-each ((pair pairs))
(mac-param-bind *match-form* (key val) pair
(let ((key-pat-p (non-triv-pat-p key))
(val-pat-p (non-triv-pat-p val))
(key-var-sym (var-pat-p key)))
(cond
((and key-var-sym var-list.(exists key-var-sym))
(let ((vm (compile-match val (gensym "val") var-list))
(val-sym (gensym "val")))
vm.(add-guards-pre
(new match-guard
vars (list vm.obj-var)
var-exprs ^((gethash ,obj-var ,key-var-sym
,hash-alt-val))
test-expr ^(neq ,vm.obj-var
,hash-alt-val)))
vm))
((and key-pat-p val-pat-p)
(set need-alist-p t)
(compile-match ^@(coll (,key . ,val))
hash-alist-var var-list))
(key-pat-p
(let ((km (compile-match key (gensym "keys")
var-list)))
km.(add-guards-pre
(new match-guard
pure-temps (list km.obj-var)
pure-temp-exprs ^((hash-keys-of ,obj-var
',val))))
km))
(t
(let ((vm (compile-match val (gensym "val") var-list)))
vm.(add-guards-pre
(new match-guard
pure-temps (list vm.obj-var)
pure-temp-exprs ^((gethash ,obj-var ',key,
hash-alt-val))
test-expr ^(neq ,vm.obj-var ,hash-alt-val)))
vm)))))))
(guard (new match-guard
guard-expr ^(hashp ,obj-var)
vars (if need-alist-p
(list hash-alist-var))
var-exprs (if need-alist-p
(list ^(hash-alist ,obj-var))))))
(new compiled-match
pattern hash-expr
obj-var obj-var
guard-chain (cons guard (mappend .guard-chain hash-matches))))))
(defun compile-exprs-match (exprs-syntax exprs var-list)
(let ((pats (cdr exprs-syntax))
(temps (mapcar (ret (gensym)) exprs)))
(let* ((matches (mapcar (op compile-match @1 @2 var-list)
pats temps)))
(new compiled-match
pattern exprs-syntax
obj-var nil
guard-chain (cons (new match-guard
pure-temps temps
pure-temp-exprs exprs)
(mappend .guard-chain matches))))))
(defun compile-match (pat : (obj-var (gensym)) (var-list (new var-list)))
(cond
((consp pat)
(caseq (car pat)
(sys:expr
(let ((exp (cadr pat)))
(if (consp exp)
(caseq (car exp)
(struct (compile-struct-match exp obj-var var-list))
(require (compile-require-match exp obj-var var-list))
(usr:as (compile-as-match exp obj-var var-list))
(usr:with (compile-with-match exp obj-var var-list))
(all (compile-loop-match exp obj-var var-list))
(usr:all* (compile-loop-match exp obj-var var-list))
(some (compile-loop-match exp obj-var var-list))
(coll (compile-loop-match exp obj-var var-list))
(or (compile-or-match exp obj-var var-list))
(and (compile-and-match exp obj-var var-list))
(not (compile-not-match exp obj-var var-list))
(op (compile-op-match exp obj-var var-list))
(hash (compile-hash-match exp obj-var var-list))
(rcons (compile-range-match exp obj-var var-list))
(exprs (compile-exprs-match exp obj-var var-list))
(t (compile-predicate-match exp obj-var var-list)))
(compile-error *match-form*
"unrecognized pattern syntax ~s" pat))))
(sys:var (compile-var-match (cadr pat) obj-var var-list))
(t (if (non-triv-pat-p pat)
(compile-cons-structure pat obj-var var-list)
(compile-atom-match pat obj-var var-list)))))
(t (compile-atom-match pat obj-var var-list))))
(defun get-var-list (env)
(new var-list menv env))
(defmacro when-match (:form *match-form* :env e pat obj . body)
(let ((cm (compile-match pat : (get-var-list e))))
^(alet ((,cm.obj-var ,obj))
(let ,cm.(get-vars)
,cm.(wrap-guards . body)))))
(defmacro if-match (:form *match-form* :env e pat obj then : else)
(let ((cm (compile-match pat : (get-var-list e)))
(match-p (gensym "match-p-"))
(result (gensym "result-")))
^(alet ((,cm.obj-var ,obj))
(let* (,match-p ,*cm.(get-vars)
(,result ,cm.(wrap-guards
^(set ,match-p t)
then)))
(if ,match-p ,result ,else)))))
(defmacro match-case (:form *match-form* :env e obj . clauses)
(unless [all clauses [andf proper-listp [chain len plusp]]]
(compile-error *match-form* "bad clause syntax"))
(let* ((matched-p-temp (gensym "matched-p-"))
(result-temp (gensym "result-"))
(objvar (gensym "obj-"))
(var-list (get-var-list e))
(clause-matches [mapcar (op compile-match (car @1)
objvar (copy var-list))
clauses])
(nclauses (len clauses))
(clause-code (collect-each ((cl clauses)
(cm clause-matches)
(i 1))
(mac-param-bind *match-form* (match . forms) cl
^(unless ,(unless (eql i 1) matched-p-temp)
(let (,*cm.(get-vars))
(set ,result-temp
,(if (eql i nclauses)
cm.(wrap-guards . forms)
cm.(wrap-guards
^(set ,matched-p-temp t)
. forms)))))))))
^(alet ((,objvar ,obj))
(let (,matched-p-temp ,result-temp)
,*clause-code
,result-temp))))
(defmacro when-exprs-match (:form *match-form* :env e pats exprs . forms)
(let ((em (compile-match ^@(exprs ,*pats) exprs (get-var-list e))))
^(let* (,*em.(get-vars))
,em.(wrap-guards . forms))))
(defstruct lambda-clause ()
orig-syntax
fixed-patterns
variadic-pattern
nfixed
forms
(:postinit (me)
(set me.nfixed (len me.fixed-patterns))))
(defun parse-lambda-match-clause (clause)
(mac-param-bind *match-form* (args . body) clause
(cond
((atom args) (new lambda-clause
orig-syntax args
variadic-pattern args
forms body))
((proper-list-p args)
(let* ((vpos (pos-if (lop meq 'sys:expr 'sys:var) args)))
(tree-bind (fixed-pats . variadic-pat) (split args vpos)
(new lambda-clause
orig-syntax args
fixed-patterns fixed-pats
variadic-pattern (car variadic-pat)
forms body))))
(t (new lambda-clause
orig-syntax args
fixed-patterns (butlast args 0)
variadic-pattern (last args 0)
forms body)))))
(defun expand-lambda-match (clauses)
(let* ((parsed-clauses [mapcar parse-lambda-match-clause clauses])
(max-args (or [find-max parsed-clauses : .nfixed].?nfixed 0))
(min-args (or [find-min parsed-clauses : .nfixed].?nfixed 0))
(variadic [some parsed-clauses .variadic-pattern])
(fix-arg-temps (mapcar (op gensym `arg-@1`)
(range* 0 min-args)))
(opt-arg-temps (mapcar (op gensym `arg-@1`)
(range* min-args max-args)))
(rest-temp (if variadic (gensym `rest`)))
(present-p-temps (mapcar (op gensym `have-@1`)
(range* min-args max-args)))
(arg-temps (append fix-arg-temps opt-arg-temps))
(present-vec (vec-list (append (repeat '(t) min-args)
present-p-temps)))
(matched-p-temp (gensym "matched-p"))
(result-temp (gensym "result"))
(nclauses (len parsed-clauses))
(ex-clauses (collect-each ((pc parsed-clauses)
(counter 1))
(let* ((vp pc.variadic-pattern)
(exp ^(when-exprs-match
(,*pc.fixed-patterns
,*(if vp (list vp)))
(,*[arg-temps 0..pc.nfixed]
,*(if vp
^((list* ,*[arg-temps pc.nfixed..:]
,rest-temp))))
,*(unless (eql counter nclauses)
^((set ,matched-p-temp t)))
(set ,result-temp (progn ,*pc.forms)))))
(sys:set-macro-ancestor exp pc.orig-syntax)
(when (> pc.nfixed min-args)
(set exp ^(when ,[present-vec (pred pc.nfixed)]
,exp)))
(when (< pc.nfixed max-args)
(set exp ^(unless ,[present-vec pc.nfixed]
,exp)))
(when (and variadic (not vp) (= pc.nfixed max-args))
(set exp ^(unless ,rest-temp
,exp)))
(unless (eql 1 counter)
(set exp ^(unless ,matched-p-temp ,exp)))
exp))))
^(lambda (,*fix-arg-temps
,*(if opt-arg-temps
(cons : (mapcar (ret ^(,@1 nil ,@2))
opt-arg-temps present-p-temps)))
. ,rest-temp)
(let (,matched-p-temp ,result-temp)
,*ex-clauses
,result-temp))))
(defmacro lambda-match (:form *match-form* . clauses)
(expand-lambda-match clauses))
(defmacro defun-match (:form *match-form* name . clauses)
(tree-bind (lambda args . body) (expand-lambda-match clauses)
^(defun ,name ,args . ,body)))
(define-param-expander :match (params clauses menv form)
(let ((*match-form* form))
(unless (proper-list-p params)
(compile-error form
"~s is incompatible with dotted parameter lists"
:match))
(when (find : params)
(compile-error form
"~s is incompatible with optional parameters"
:match))
(tree-bind (lambda lparams . body) (expand-lambda-match clauses)
(let ((dashdash (member '-- params)))
(cons (append (ldiff params dashdash)
(butlastn 0 lparams)
dashdash
(nthlast 0 lparams))
body)))))
(defun non-triv-pat-p (syntax) t)
(defun non-triv-pat-p (syntax)
(match-case syntax
((@(eq 'sys:expr) (@(bindable) . @nil)) t)
((@(eq 'sys:var) @(or @(bindable) nil) . @nil) t)
((@pat . @rest) (or (non-triv-pat-p pat)
(non-triv-pat-p rest)))
(#R(@from @to) (or (non-triv-pat-p from)
(non-triv-pat-p to)))
(@(some @(non-triv-pat-p)) t)))
(defun var-pat-p (syntax)
(when-match (@(eq 'sys:var) @(bindable @sym) . @nil) syntax
sym))
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