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1.3.0

tree-seq

Returns a lazy sequence of the nodes in a tree, via a depth-first walk.
branch? must be a fn of one arg that returns true if passed a node
that can have children (but may not). children must be a fn of one
arg that returns a sequence of the children. Will only be called on
nodes for which branch? returns true. Root is the root node of the
tree.

5 Examples top

link | changes
```
;; Each node is a number or a seq, 
;; so branch?==seq? and children==identity
;; 
;;     .
;;    / \
;;   .   .
;;  /|\  |
;; 1 2 . 4
;;     |  
;;     3
;;

user=> (tree-seq seq? identity '((1 2 (3)) (4)))

(((1 2 (3)) (4)) (1 2 (3)) 1 2 (3) 3 (4) 4)
```
;; Each node is a number or a seq, ;; so branch?==seq? and children==identity ;; ;; . ;; / \ ;; . . ;; /|\ | ;; 1 2 . 4 ;; | ;; 3 ;; user=> (tree-seq seq? identity '((1 2 (3)) (4))) (((1 2 (3)) (4)) (1 2 (3)) 1 2 (3) 3 (4) 4)
link | changes
```
user=> (tree-seq map? #(interleave (keys %) (vals %)) {:a 1 :b {:c 3 :d 4 :e {:f 6 :g 7}}})

({:a 1, :b {:c 3, :d 4, :e {:f 6, :g 7}}} :a 1 :b {:c 3, :d 4, :e {:f 6, :g 7}} :c 3 :d 4 :e {:f 6, :g 7} :f 6 :g 7)
```
user=> (tree-seq map? #(interleave (keys %) (vals %)) {:a 1 :b {:c 3 :d 4 :e {:f 6 :g 7}}}) ({:a 1, :b {:c 3, :d 4, :e {:f 6, :g 7}}} :a 1 :b {:c 3, :d 4, :e {:f 6, :g 7}} :c 3 :d 4 :e {:f 6, :g 7} :f 6 :g 7)
link | changes
```
;; Each node is a (node-root child1 child2 ...),
;; so branch?==next and children==rest
;;
;;     A
;;    / \
;;   B   C
;;  / \  |
;; D   E F
;;
user=> (map first (tree-seq next rest '(:A (:B (:D) (:E)) (:C (:F)))))

(:A :B :D :E :C :F)
```
;; Each node is a (node-root child1 child2 ...), ;; so branch?==next and children==rest ;; ;; A ;; / \ ;; B C ;; / \ | ;; D E F ;; user=> (map first (tree-seq next rest '(:A (:B (:D) (:E)) (:C (:F))))) (:A :B :D :E :C :F)
link | changes
```
;; FYI, previous example doesn't always work:
;;
user> (map first (tree-seq next rest '((1 2 (3)) (4))))
((1 2 (3)) 4)
```
;; FYI, previous example doesn't always work: ;; user> (map first (tree-seq next rest '((1 2 (3)) (4)))) ((1 2 (3)) 4)
link | changes
```
user=> (tree-seq seq? seq [[1 2 [3]] [4]])
([[1 2 [3]] [4]])

user=> (tree-seq vector? seq [[1 2 [3]] [4]])
([[1 2 [3]] [4]] [1 2 [3]] 1 2 [3] 3 [4] 4)

user=> (tree-seq seq? seq '((1 2 (3)) (4)))
(((1 2 (3)) (4)) (1 2 (3)) 1 2 (3) 3 (4) 4)
```
user=> (tree-seq seq? seq [[1 2 [3]] [4]]) ([[1 2 [3]] [4]]) user=> (tree-seq vector? seq [[1 2 [3]] [4]]) ([[1 2 [3]] [4]] [1 2 [3]] 1 2 [3] 3 [4] 4) user=> (tree-seq seq? seq '((1 2 (3)) (4))) (((1 2 (3)) (4)) (1 2 (3)) 1 2 (3) 3 (4) 4)

Source clojure/core.clj:4337 top

(defn tree-seq
  "Returns a lazy sequence of the nodes in a tree, via a depth-first walk.
   branch? must be a fn of one arg that returns true if passed a node
   that can have children (but may not).  children must be a fn of one
   arg that returns a sequence of the children. Will only be called on
   nodes for which branch? returns true. Root is the root node of the
  tree."
  {:added "1.0"
   :static true}
   [branch? children root]
   (let [walk (fn walk [node]
                (lazy-seq
                 (cons node
                  (when (branch? node)
                    (mapcat walk (children node))))))]
     (walk root)))

Vars in clojure.core/tree-seq:

Used in 0 other vars

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Clojure Core

Namespaces

tree-seq

clojure.core

5 Examples top

See Also top

Source clojure/core.clj:4337 top

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