Persistent-hash-trie NPM

persistent-hash-trie

Pure string:val storage, using structural sharing.

Why

This module forms a possible basis for effecient persistent datastructures; such as those found in Clojure's PersistentHashMap and PersistentVector.

Install

npm install persistent-hash-trie

Docs

Trie

var p = require('persistent-hash-trie')

var trie = p.Trie()

assoc

Returns a new Trie with the new key:value keys added.

var trie1 = p.Trie()
var trie2 = p.assoc(trie1, 'key', { value: true })

dissoc

Returns a new Trie without a specific key

var trie1 = p.assoc(p.Trie(), 'key', 'val')
var trie2 = p.dissoc(trie2, 'key')

get

Retrieves a value from a Trie.

var trie = p.assoc(p.Trie(), 'key', 'val')
p.get(trie, 'key') //= 'val'

has

Returns true or false, depending on whether the value is in the Trie.

var trie = p.assoc(p.Trie(), 'key', 'val')
p.has(trie, 'key') 		//= true
p.has(trie, 'not-in-here') //= false

transient

Returns a mutable copy of a Trie, in the form of a js object.

var trie = p.assoc(p.Trie(), 'key', 'val')
p.transient(trie) //= { key: 'val' }

Extending assoc/dissoc/get/has

The hashing and equality functions used on the keys can be overidden by passing an opts object to assoc, dissoc, get and has.

var im = require('persistent-hash-trie')

var opts = {
	eq: function(a, b){ return a === b},
	hash: function(key){ return parseInt(key, 10) }
}

var vector = p.assoc(p.Trie(), 3, 'my-val', opts)
var val = p.get(vector, 3, opts)
var vector2 = p.dissoc(vector, 3, opts)
p.has(vector2, 3, opts) // false