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; Copyright (c) Chris Houser, April 2008. 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.
; System for filtering trees and nodes generated by zip.clj in
; general, and xml trees in particular.
(ns
^{:author "Chris Houser",
:doc "System for filtering trees and nodes generated by zip.clj in
general, and xml trees in particular.
"}
clojure.contrib.zip-filter
(:refer-clojure :exclude (descendants ancestors))
(:require [clojure.zip :as zip]))
; This uses the negative form (no-auto) so that the result from any
; naive function, including user functions, defaults to "auto".
(defn auto
[v x] (with-meta x ((if v dissoc assoc) (meta x) :zip-filter/no-auto? true)))
(defn auto?
[x] (not (:zip-filter/no-auto? (meta x))))
(defn right-locs
"Returns a lazy sequence of locations to the right of loc, starting with loc."
[loc] (lazy-seq (when loc (cons (auto false loc) (right-locs (zip/right loc))))))
(defn left-locs
"Returns a lazy sequence of locations to the left of loc, starting with loc."
[loc] (lazy-seq (when loc (cons (auto false loc) (left-locs (zip/left loc))))))
(defn leftmost?
"Returns true if there are no more nodes to the left of location loc."
[loc] (nil? (zip/left loc)))
(defn rightmost?
"Returns true if there are no more nodes to the right of location loc."
[loc] (nil? (zip/right loc)))
(defn children
"Returns a lazy sequence of all immediate children of location loc,
left-to-right."
[loc]
(when (zip/branch? loc)
(map #(auto false %) (right-locs (zip/down loc)))))
(defn children-auto
"Returns a lazy sequence of all immediate children of location loc,
left-to-right, marked so that a following tag= predicate will auto-descend."
^{:private true}
[loc]
(when (zip/branch? loc)
(map #(auto true %) (right-locs (zip/down loc)))))
(defn descendants
"Returns a lazy sequence of all descendants of location loc, in
depth-first order, left-to-right, starting with loc."
[loc] (lazy-seq (cons (auto false loc) (mapcat descendants (children loc)))))
(defn ancestors
"Returns a lazy sequence of all ancestors of location loc, starting
with loc and proceeding to loc's parent node and on through to the
root of the tree."
[loc] (lazy-seq (when loc (cons (auto false loc) (ancestors (zip/up loc))))))
(defn- fixup-apply
"Calls (pred loc), and then converts the result to the 'appropriate'
sequence."
^{:private true}
[pred loc]
(let [rtn (pred loc)]
(cond (and (map? (meta rtn)) (:zip-filter/is-node? (meta rtn))) (list rtn)
(= rtn true) (list loc)
(= rtn false) nil
(nil? rtn) nil
(sequential? rtn) rtn
:else (list rtn))))
(defn mapcat-chain
^{:private true}
[loc preds mkpred]
(reduce (fn [prevseq expr]
(mapcat #(fixup-apply (or (mkpred expr) expr) %) prevseq))
(list (with-meta loc (assoc (meta loc) :zip-filter/is-node? true)))
preds))
; see clojure.contrib.zip-filter.xml for examples
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