Created
September 21, 2010 13:38
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Avoid forcing lazy seqs when printing
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; Copyright (c) Rich Hickey. All rights reserved. | |
; The use and distribution terms for this software are covered by the | |
; Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php) | |
; which can be found in the file epl-v10.html at the root of this distribution. | |
; By using this software in any fashion, you are agreeing to be bound by | |
; the terms of this license. | |
; You must not remove this notice, or any other, from this software. | |
; modified by Chris Houser | |
(require '[clojure.contrib.reflect :as hack]) | |
(def *print-force-lazy* false) | |
(defn unrealized? [x] | |
(and (instance? clojure.lang.LazySeq x) | |
(hack/get-field clojure.lang.LazySeq "fn" x))) | |
(defn print-lazy-sequential [^String begin, print-one, ^String sep, ^String end, sequence, ^java.io.Writer w] | |
(binding [*print-level* (and (not *print-dup*) *print-level* (dec *print-level*))] | |
(if (and *print-level* (neg? *print-level*)) | |
(.write w "#") | |
(do | |
(.write w begin) | |
(if (unrealized? sequence) | |
(.write w "...unrealized...") | |
(when-let [xs (seq sequence)] | |
(loop [xs xs | |
print-length (or *print-length* 0)] | |
(if (and (not *print-dup*) *print-length* (zero? print-length)) | |
(.write w "...") | |
(do | |
(print-one (first xs) w) | |
(if (unrealized? (rest xs)) | |
(.write w " ...unrealized...") | |
(when-let [xs (next xs)] | |
(.write w sep) | |
(recur xs (dec print-length))))))))) | |
(.write w end))))) | |
(defmethod print-method clojure.lang.ISeq [o, ^java.io.Writer w] | |
(#'clojure.core/print-meta o w) | |
(if *print-force-lazy* | |
(#'clojure.core/print-sequential "(" #'clojure.core/pr-on " " ")" o w) | |
(print-lazy-sequential "(" #'clojure.core/pr-on " " ")" o w))) | |
(map identity '(0 1 2 3)) | |
;=> (...unrealized...) | |
(next (map identity '(0 1 2 3))) | |
;=> (1 ...unrealized...) | |
(rest (map identity (vec (range 100)))) | |
;=> (1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 ...unrealized...) | |
(def vs (map identity (vec (range 100)))) | |
vs | |
;=> (...unrealized...) | |
(first vs) | |
;=> 0 | |
vs | |
;=> (0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 ...unrealized...) |
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