(defn gen-pvec [pb]
(fn [bvec b val]
(let [gvec (gensym "vec__")
gseq (gensym "seq__")
gfirst (gensym "first__")
has-rest (some #{'&} b)]
(loop [ret (let [ret (conj bvec gvec val)]
(if has-rest
(conj ret gseq (list `seq gvec))
ret))
n 0
bs b
seen-rest? false]
(if (seq bs)
(let [firstb (first bs)]
(cond
(= firstb '&) (recur (pb ret (second bs) gseq)
n
(nnext bs)
true)
(= firstb :as) (pb ret (second bs) gvec)
:else (if seen-rest?
(throw (new Exception "Unsupported binding form, only :as
can follow & parameter"))
(recur (pb (if has-rest
(conj ret
gfirst `(first ~gseq)
gseq `(next ~gseq))
ret)
firstb
(if has-rest
gfirst
(list `nth gvec n nil)))
(inc n)
(next bs)
seen-rest?))))
ret))))
)
(defn gen-bes [b]
(let [transforms
(reduce1
(fn [transforms mk]
(if (keyword? mk)
(let [mkns (namespace mk)
mkn (name mk)]
(cond (= mkn "keys") (assoc transforms mk #(keyword (or mkns
(namespace %)) (name %)))
(= mkn "syms") (assoc transforms mk #(list `quote (symbol
(or mkns (namespace %)) (name %))))
(= mkn "strs") (assoc transforms mk str)
:else transforms))
transforms))
{}
(keys b))]
(reduce1
(fn [bes entry]
(reduce1 #(assoc %1 %2 ((val entry) %2))
(dissoc bes (key entry))
((key entry) bes)))
(dissoc b :as :or)
transforms))
)
(defn gen-pmap [pb]
(fn [bvec b v]
(let [gmap (gensym "map__")
gmapseq (with-meta gmap {:tag 'clojure.lang.ISeq})
defaults (:or b)]
(loop [ret (-> bvec (conj gmap) (conj v)
(conj gmap) (conj `(if (seq? ~gmap)
(clojure.lang.PersistentHashMap/create (seq ~gmapseq)) ~gmap))
((fn [ret]
(if (:as b)
(conj ret (:as b) gmap)
ret))))
bes (gen-bes b)]
(if (seq bes)
(let [bb (key (first bes))
bk (val (first bes))
local (if (instance? clojure.lang.Named bb) (with-meta (symbol
nil (name bb)) (meta bb)) bb)
bv (if (contains? defaults local)
(list `get gmap bk (defaults local))
(list `get gmap bk))]
(recur (if (ident? bb)
(-> ret (conj local bv))
(pb ret bb bv))
(next bes)))
ret))))
)
(defn pb []
(fn pb [bvec b v]
(let [pvec (gen-pvec pb)
pmap (gen-pmap pb)]
(cond
(symbol? b) (-> bvec (conj b) (conj v))
(vector? b) (pvec bvec b v)
(map? b) (pmap bvec b v)
:else (throw (new Exception (str "Unsupported binding form: " b))))))
)
(defn destructure [bindings]
(let [bents (partition 2 bindings)
pb (pb)
process-entry (fn [bvec b] (pb bvec (first b) (second b)))]
(if (every? symbol? (map first bents))
bindings
(reduce1 process-entry [] bents))))
(fact "重构clojure destructure" :destructure
(destructure '[a 3]) => '[a 3]
(destructure '[[a b] ["a" "b"]]) => 2
)
the refactor clojure.core/destructure It's a bit big function.
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