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;;; seq-utils.clj -- Sequence utilities for Clojure
;; by Stuart Sierra <mail@stuartsierra.com>
;; April 8, 2008
;; Copyright (c) 2008 Stuart Sierra. All rights reserved. The use and
;; distribution terms for this software are covered by the Common
;; Public License 1.0 (http://www.opensource.org/licenses/cpl1.0.php)
;; which can be found in the file CPL.TXT 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.
(clojure/in-ns 'seq-utils)
(clojure/refer 'clojure)
;; 'flatten' written by Rich Hickey,
;; see http://groups.google.com/group/clojure/msg/385098fabfcaad9b
(defn flatten
"Takes any nested combination of sequential things (lists, vectors,
etc.) and returns their contents as a single, flat sequence."
[x]
(let [s? #(instance? clojure.lang.Sequential %)]
(filter (complement s?) (tree-seq s? seq x))))
(defn batch
"Returns a sequence of sequences, each containing 'size' elements
from s."
[size s]
(when s
(lazy-cons (take size s) (batch size (drop size s)))))
(defn separate
"Returns a vector:
[ (filter f s), (filter (complement f) s) ]"
[f s]
[(filter f s) (filter (complement f) s)])
(defn includes?
"Returns true if s contains something equal (with =) to x."
[x s]
(if (some (fn [y] (= y x)) s)
true false))
(defn indexed
"Returns a lazy sequence of [index, item] pairs, where items come
from 's' and indexes count up from zero.
(indexed '(a b c d)) => ([0 a] [1 b] [2 c] [3 d])"
[s]
(map vector (iterate inc 0) s))
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