azip

A Clojure library providing zippers for labeled unordered trees, such as nested maps.

This library is modeled after clojure.zip, with the set of navigators slightly adjusted.

Usage

The coordinates of the library:

[mg.dt/azip "0.1.0"]

The namespace of the library:

(require '[mg.dt.azip :as azip])

Given a nested map structure

user=> (def data {:child-a {:leaf-a "a" :leaf-b "b"} :child-b {}})
#'user/data

create a zipper using map-azip (generic azipper is available too)

user=> (def rootz (azip/map-azip data))
#'user/rootz

Navigators for moving the zipper are called down and up

user=> (def childz (azip/down rootz :child-a))
#'user/childz
user=> (def leafz (azip/down childz :leaf-a))
#'user/leafz
user=> (= (azip/up leafz) childz)
true

You can use branch?, node, children, down? to interrogate the state of zipper

user=> (azip/branch? childz)
true
user=> (azip/branch? leafz)
false
user=> (azip/node rootz)
{:child-a {:leaf-a "a", :leaf-b "b"}, :child-b {}}
user=> (azip/node childz)
{:leaf-a "a", :leaf-b "b"}
user=> (azip/children rootz)
(:child-a :child-b)
user=> (azip/down? rootz :child-a)
true
user=> (azip/down? rootz :missing)
false

insert adds a new child at the current position of the zipper, replacing existing child if it exists

user=> (-> rootz (azip/insert :newkey :newval)
                 (azip/node))
{:child-a {:leaf-a "a", :leaf-b "b"}, :child-b {}, :newkey :newval}
user=> (-> rootz (azip/insert :child-a :newval)
                (azip/node))
{:child-a :newval, :child-b {}}

replace and edit change the current node

user=> (-> childz (azip/replace :rep)
                  (azip/up)
                  (azip/node))
{:child-a :rep, :child-b {}}
user=> (-> leafz (azip/edit (fn [node arg] arg) :rep)
                 (azip/up)
                 (azip/up)
                 (azip/node))
{:child-a {:leaf-a :rep, :leaf-b "b"}, :child-b {}}

root is a shortcut to move the zipper to the top and return the whole data structure

user=> (-> leafz (azip/replace :rep) (azip/root))
{:child-a {:leaf-a :rep, :leaf-b "b"} :child-b {}}

License

Copyright © 2017 Mikhail Gusarov dottedmag@dottedmag.net

Distributed under the MIT license.