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[lazy] got rid of lazy-cons
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@richhickey
richhickey committed Feb 2, 2009
1 parent a91249e commit 47304c2
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Showing 2 changed files with 53 additions and 55 deletions.
101 changes: 49 additions & 52 deletions src/clj/clojure/core.clj
View file
Expand Up @@ -397,16 +397,6 @@
[item & more]
(spread (cons item more)))

(defmacro lazy-cons
"Expands to code which produces a seq object whose first is
first-expr and whose rest is rest-expr, neither of which is
evaluated until first/rest is called. Each expr will be evaluated at most
once per step in the sequence, e.g. calling first/rest repeatedly on the
same node of the seq evaluates first/rest-expr once - the values they yield are
cached."
[first-expr & rest-expr]
(list 'new 'clojure.lang.LazyCons (list `fn (list [] first-expr) (list* [(gensym)] rest-expr))))

(defmacro lazy-seq
"Takes a body of expressions that returns an ISeq or nil, and yields
a Seqable object that will invoke the body only the first time seq
Expand Down Expand Up @@ -2586,14 +2576,11 @@
(defmacro lazy-cat
"Expands to code which yields a lazy sequence of the concatenation
of the supplied colls. Each coll expr is not evaluated until it is
needed."
([coll] `(seq ~coll))
([coll & colls]
`(let [iter# (fn iter# [coll#]
(if (seq coll#)
(lazy-cons (first coll#) (iter# (rest coll#)))
(lazy-cat ~@colls)))]
(iter# ~coll))))
needed.
(lazy-cat xs ys zs) === (concat (lazy-seq xs) (lazy-seq ys) (lazy-seq zs))"
[& colls]
`(concat ~@(map #(list `lazy-seq %) colls)))

(defmacro for
"List comprehension. Takes a vector of one or more
Expand All @@ -2617,17 +2604,19 @@
emit (fn emit [[group & [{next-seq :seq} :as more-groups]]]
(let [giter (gensym "iter__") gxs (gensym "s__")]
`(fn ~giter [~gxs]
(when-first [~(:bind group) ~gxs]
(when ~(or (:while group) true)
(if ~(or (:when group) true)
~(if more-groups
`(let [iterys# ~(emit more-groups)
fs# (iterys# ~next-seq)]
(if fs#
(lazy-cat fs# (~giter (rest ~gxs)))
(recur (rest ~gxs))))
`(lazy-cons ~expr (~giter (rest ~gxs))))
(recur (rest ~gxs))))))))]
(lazy-seq
(loop [~gxs ~gxs]
(when-first [~(:bind group) ~gxs]
(when ~(or (:while group) true)
(if ~(or (:when group) true)
~(if more-groups
`(let [iterys# ~(emit more-groups)
fs# (seq (iterys# ~next-seq))]
(if fs#
(concat fs# (~giter (more ~gxs)))
(recur (more ~gxs))))
`(cons ~expr (~giter (more ~gxs))))
(recur (more ~gxs))))))))))]
`(let [iter# ~(emit (to-groups seq-exprs))]
(iter# ~(second seq-exprs))))))

Expand Down Expand Up @@ -2733,8 +2722,9 @@
[#^java.util.regex.Pattern re s]
(let [m (re-matcher re s)]
((fn step []
(when (. m (find))
(lazy-cons (re-groups m) (step)))))))
(lazy-seq
(when (. m (find))
(cons (re-groups m) (step))))))))

(defn re-matches
"Returns the match, if any, of string to pattern, using
Expand Down Expand Up @@ -2842,9 +2832,10 @@
tree."
[branch? children root]
(let [walk (fn walk [node]
(lazy-cons node
(lazy-seq
(cons node
(when (branch? node)
(mapcat walk (children node)))))]
(mapcat walk (children node))))))]
(walk root)))

(defn file-seq
Expand Down Expand Up @@ -2907,11 +2898,14 @@
(defn distinct
"Returns a lazy sequence of the elements of coll with duplicates removed"
[coll]
(let [step (fn step [[f & r :as xs] seen]
(when xs
(if (seen f) (recur r seen)
(lazy-cons f (step r (conj seen f))))))]
(step (seq coll) #{})))
(let [step (fn step [xs seen]
(lazy-seq
(loop [[f :as xs] xs seen seen]
(when (seq xs)
(if (seen f)
(recur (more xs) seen)
(cons f (step (more xs) (conj seen f))))))))]
(step coll #{})))

(defmacro if-let
"bindings => binding-form test
Expand Down Expand Up @@ -3021,7 +3015,7 @@
(defn repeatedly
"Takes a function of no args, presumably with side effects, and returns an infinite
lazy sequence of calls to it"
[f] (lazy-cons (f) (repeatedly f)))
[f] (lazy-seq (cons (f) (repeatedly f))))

(defn add-classpath
"Adds the url (String or URL object) to the classpath per URLClassLoader.addURL"
Expand Down Expand Up @@ -3150,12 +3144,13 @@
(.put q q)
(throw e))))
drain (fn drain []
(let [x (.take q)]
(if (identical? x q) ;q itself is eos sentinel
@agt ;will be nil - touch agent just to propagate errors
(do
(send-off agt fill)
(lazy-cons (if (identical? x NIL) nil x) (drain))))))]
(lazy-seq
(let [x (.take q)]
(if (identical? x q) ;q itself is eos sentinel
@agt ;will be nil - touch agent just to propagate errors
(do
(send-off agt fill)
(cons (if (identical? x NIL) nil x) (drain)))))))]
(send-off agt fill)
(drain))))

Expand Down Expand Up @@ -3738,16 +3733,18 @@
wget (fn [a] (await1 a) @a)
step (fn step [[x & xs :as s]
[a & as :as acycle]]
(if s
(let [v (wget a)]
(send a (fn [_] (f x)))
(lazy-cons v (step xs as)))
(map wget (take (count agents) acycle))))]
(lazy-seq
(if s
(let [v (wget a)]
(send a (fn [_] (f x)))
(cons v (step xs as)))
(map wget (take (count agents) acycle)))))]
(step (drop n coll) (cycle agents))))
([f coll & colls]
(let [step (fn step [cs]
(when (every? seq cs)
(lazy-cons (map first cs) (step (map rest cs)))))]
(lazy-seq
(when (every? seq cs)
(cons (map first cs) (step (map rest cs))))))]
(pmap #(apply f %) (step (cons coll colls))))))

(def
Expand Down
7 changes: 4 additions & 3 deletions src/clj/clojure/core_proxy.clj
View file
Expand Up @@ -338,9 +338,10 @@
(assoc [k v] (assoc (snapshot) k v))
(without [k] (dissoc (snapshot) k))
(seq [] ((fn thisfn [pseq]
(when pseq
(lazy-cons (new clojure.lang.MapEntry (first pseq) (v (first pseq)))
(thisfn (rest pseq))))) (keys pmap))))))
(lazy-seq
(when pseq
(cons (new clojure.lang.MapEntry (first pseq) (v (first pseq)))
(thisfn (more pseq))))) (keys pmap)))))))



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