clojure - get combinations of vector elements -


i wander if there reducer in clojure can give same result below function without using recursion

the function should take vector , returns combinations of items (e.g. giving [1 2 3] , returns ((1 2 3) (1 2) (1 3) (1) (2 3) (2) (3) []))

(def combinations "creates combinations of items example [1 2 3] generate ((1 2 3) (1 2) (1 3) (1) (2 3) (2) (3) [])" (memoize (fn[items] (if (empty? items) [[]] (let [els (combinations (rest items))]     (concat  (map #(cons (first items) %)els) els))))))

an alternative approach use clojure math lib.

for leiningen project.clj add this- [org.clojure/math.combinatorics "0.1.3"]

to use-

(ns example.core   (:require [clojure.math.combinatorics :as c]))  (c/subsets [1 2 3]) ;;=> (() (1) (2) (3) (1 2) (1 3) (2 3) (1 2 3))

you can see source code here recursion-less solution if don't want lib.


-

Comments

Post a Comment

Popular posts from this blog

angular - Is it possible to get native element for formControl? -

i've got angular2 reactive form . created formcontrol s , assigned input fields by [formcontrol]=... . understand creates nativeelement <-> formcontrol link. my question: possible nativeelement formcontrol ? wanna myformcontrol.nativeelement.focus() i can share 1 terrible solution works me. in reactive forms can use either 1) formcontroldirective ts mycontrol = new formcontrol('') template <input type="text" [formcontrol]="mycontrol"> or 2) formcontrolname ts myform: formgroup; constructor(private fb: formbuilder) {} ngoninit() { this.myform = this.fb.group({ foo: '' }); } template <form [formgroup]="myform"> <input type="text" formcontrolname="foo"> </form> so these directives write patch like 1) formcontroldirective const originformcontrolngonchanges = formcontroldirective.prototype.ngonchanges; formcontroldirective.proto
Read more

unity3d - Rotate an object to face an opposite direction -

i have object , b. when click on object b, rotates object b (a faces b). b doesn't face a. need following : when faces b, need face opposite direction. have code rotating @ b. how rotate face opposite direction after that? vector3 targetdirection = target - transform.position; float step = speed * time.deltatime; vector3 newdirection = vector3.rotatetowards (turretdome.transform.forward, targetdirection, step, 0.0f); turretdome.transform.rotation = quaternion.lookrotation (newdirection); you object facing object b, want inverse direction of object after that? objecta.transform.rotation = quaternion.inverse(objecta.transform.rotation) but lets assume example turretdome object a, (negate direction): turretdome.transform.rotation = quaternion.lookrotation (-newdirection); naturally, both of these snippets not show how smoothen rotation, seem know how use time.deltatime. just incase unsure, quaternion.lerp this
Read more

javascript - Why jQuery Select box change event is now working? -

i working on product filters user select select box according his/her preference not getting selected value user in jquery. html code:- <select name="product_filter" id="product_filter"> <option value="price_low_first">price : low high</option> <option value="price_high_first">price : high low</option> <option value="latest">latest</option> <option value="popular">most popular</option> </select> jquery code: $(function () { $("#product_filter").change(function () { alert("hi") var selectedtext = $(this).find("option:selected").text(); var selectedvalue = $(this).val(); alert("selected text: " + selectedtext + " value: " + selectedvalue); }); }); hi believe code perfect. once please check jquery.min.js
Read more