It seems to me that neither filt-split nor filter-rem from e are lazy
operations (one uses reduce, the other one uses recur).
The version in clojurecontrib seems to preserve the original property of
filter of returning a lazy sequence.
My 0,02€,
--
Laurent
2009/3/8 Adrian Cuthbertson <adrian.cuthbert...@gmail.com>
>
> That's the beauty of this language - there are many ways to skin the cat!
> Here's a version using reduce...
>
> (defn filt-split [pred col]
> (reduce (fn [[a b] x] (if (pred x) [(conj a x) b] [a (conj b x)]))
> [[] []] col))
>
> (filt-split even? [1 2 3 4 5 6 7 8])
> [[2 4 6 8] [1 3 5 7]]
>
> But when you look at separate in clojure.contrib.seq-utils its simple
> and elegant;
> (defn separate [f s]
> [(filter f s) (filter (complement f) s)])
> Rgds, Adrian.
> - Afficher le texte des messages précédents -
>
> On Sun, Mar 8, 2009 at 6:44 AM, e <evier...@gmail.com> wrote:
> > check the discussion with the subject, "time lies, even with doall". We
> > came up with something like the following, but some name change change
> > tweaks were suggested. This thing takes a pred and a collection and
> returns
> > a list of two collections -- one that passes the pred, and one that
> fails.
> >
> > (defn filt-rem [pred coll]
> > (loop [l1 () l2 () [f & r] coll]
> > (if f
> > (if (pred f)
> > (recur (conj l1 f) l2 r)
> > (recur l1 (conj l2 f) r))
> > (list l1 l2))))
> >
> >
> > On Sat, Mar 7, 2009 at 11:37 PM, Jeffrey Straszheim
> > <straszheimjeff...@gmail.com> wrote:
> >>
> >> There is separate in seq_utils in contrib.
> >>
> >> On Sat, Mar 7, 2009 at 11:29 PM, David Sletten <da...@bosatsu.net>
> wrote:
> >>>
> >>> I'm reading the Sequences chapter of Programming Clojure, and Stu
> >>> points out that split-with combines the semantics of take-while and
> >>> drop-while. But is there a function that does something similar with
> >>> "filter"? Namely, rather than simply filtering the elements of a
> >>> collection that satisfy a predicate I also want to capture those that
> >>> don't. Something like this:
> >>> (defn filter-split [pred coll]
> >>> (loop [trues '() falses '() coll coll]
> >>> (cond (empty? coll)
> >>> (vector (reverse trues) (reverse falses))
> >>> (pred (first coll))
> >>> (recur (cons (first coll) trues) falses (rest coll))
> >>> :else
> >>> (recur trues (cons (first coll) falses) (rest coll)))))
> >>>
> >>> (filter-split #{\a\e\i\o\u} "is this not pung?") => [(\i \i \o \u)
> >>> (\s \space \t \h \s \space \n \t \space \p \n \g \?)]
> >>> (filter-split even? (range 10)) => [(0 2 4 6 8) (1 3 5 7 9)]
> >>>
> >>> Aloha,
> >>> David Sletten
> >>>
> >>>
> >>
> >>
> >>
> >
> >
> > >
> >
>
> >
>
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