Ah, and also it's not lazy, e.g. : (take 10 (reduce #(concat %1 (if (> %2 6) [ :foo %2] [%2])) [] (iterate inc 0))))
Since you invited comments, please note that the quick way of writing a literal list '(3 4 5 6 8) is not general, because it does not evaluate the elements of the list : Try (let [a 0] '(a 1 2 3)) for example and you may (or may not, I remember I was, since it is a so much spread idiom) be surprised. The version that will always give what you expect is just with function list : (let [a 0] (list a 1 2 3)) HTH, -- Laurent will never return, for example. 2009/4/23 Laurent PETIT <laurent.pe...@gmail.com>: > 1:2 user=> (reduce #(concat %1 (if (> %2 6) [ :foo %2] [%2])) [] '(3 4 5 8 4 > 2)) > (3 4 5 :foo 8 4 2) > > Not good, the expected result would have been > (3 4 5 :foo 8 4 2 :foo) > > Regards, > > -- > Laurent > > 2009/4/23 Emeka <emekami...@gmail.com>: >> >> (reduce #(concat %1 (if (> %2 6) [ :foo %2] [%2])) [] '(3 4 5 8 4 2)) >> >> Note that I am not a programmer and do not know much about writing code, >> however the above snippet in my view can achieve the result you desired. I >> invite comments on the above. >> >> Regards, >> Emeka >> On Thu, Apr 23, 2009 at 10:52 AM, Christophe Grand <christo...@cgrand.net> >> wrote: >>> >>> *Warning this message contains mutable state and may hurt functional >>> sensibilities.* >>> >>> Ugly hack: >>> >>> (defn my-split-with [pred coll] >>> (let [s (atom coll) >>> p #(when-let [r (pred %)] (swap! s rest) r)] >>> [(take-while p coll) (drop-while pred (lazy-seq @s))])) >>> >>> Now it works ;-) >>> >>> Laurent PETIT a écrit : >>> > This is a general problem with function (split-with) (and derivatives >>> > such as partition-by ...), >>> > >>> > This should certainly deserve a mention in their respective >>> > docstrings, I think. Because the docstring speak about lazyness, but >>> > not the kind of lazyness that can avoid Out of Memory in corner cases. >>> > >>> > Rich, if you agree with that, would you me to issue a patch on google >>> > group ? >>> > >>> > 2009/4/23 Christophe Grand <christo...@cgrand.net>: >>> > >>> >> Laurent PETIT a écrit : >>> >> >>> >>> Hi Meikel, >>> >>> >>> >>> It seems to me that your version is the only safe one so far, that >>> >>> would succesfully indefinitely return values with this test: >>> >>> >>> >>> (dorun (mystery-function true? :foo (repeat true))) >>> >>> >>> >>> Mine, a new version of mine I'll never bother to publish, and >>> >>> Christophe's all retain head. >>> >>> To explain on Christophe's one for example: >>> >>> >>> >>> It uses (split-with) which, in case pred always match coll elements, >>> >>> will retain the head of coll in etc, while eating more and more >>> >>> elements of coll via running on run : >>> >>> 1:21 user=> (defn mystery-function [pred coll] >>> >>> (lazy-seq >>> >>> (when (seq coll) >>> >>> (let [[run etc] (split-with pred coll)] >>> >>> (if (seq run) >>> >>> (concat run (cons :foo (mystery-function pred etc))) >>> >>> (cons (first coll) (mystery-function pred (rest coll)))))))) >>> >>> 1:22 user=> (dorun (mystery-function true? (repeat true))) >>> >>> java.lang.OutOfMemoryError: GC overhead limit exceeded (repl-1:22) >>> >>> >>> >>> >>> >> Nice catch! >>> >> >>> >> >>> >> -- >>> >> Professional: http://cgrand.net/ (fr) >>> >> On Clojure: http://clj-me.blogspot.com/ (en) >>> >> >>> >> >>> >> >>> >> >>> > >>> > > >>> > >>> > >>> >>> >>> -- >>> Professional: http://cgrand.net/ (fr) >>> On Clojure: http://clj-me.blogspot.com/ (en) >>> >>> >>> >>> >> >> >> >> >> > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~----------~----~----~----~------~----~------~--~---
