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  • How do I handle priority and propagation in an event system?

    - by Peeter
    Lets say I have a simple event system with the following syntax: object = new Object(); object.bind("my_trigger", function() { print "hello"; }); object.bind("my_trigger", function() { print "hello2"; }); object.trigger("my_trigger"); How could I make sure hello2 is printed out first (I do not want my code to depend on which order the events are binded). Ontop of that, how would I prevent my events from propagating (e.g. I want to stop every other event from being executed)

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  • Getting the ID of an object when the object is given

    - by Pieter
    I have link that calls a function when clicked: <a href="javascript:spawnMenu(this);" id="link1">Test1</a> To make my function work, I need access to the object so that I can perform jQuery operations like this: alert($(objCaller).offset().left); Since objCaller points to the object and not the object ID, this won't work. I need something like this: alert($("a#link1").offset().left); How can I get the object ID from objCaller?

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  • Class instance clustering in object reference graph for multi-entries serialization

    - by Juh_
    My question is on the best way to cluster a graph of class instances (i.e. objects, the graph nodes) linked by object references (the -directed- edges of the graph) around specifically marked objects. To explain better my question, let me explain my motivation: I currently use a moderately complex system to serialize the data used in my projects: "marked" objects have a specific attributes which stores a "saving entry": the path to an associated file on disc (but it could be done for any storage type providing the suitable interface) Those object can then be serialized automatically (eg: obj.save()) The serialization of a marked object 'a' contains implicitly all objects 'b' for which 'a' has a reference to, directly s.t: a.b = b, or indirectly s.t.: a.c.b = b for some object 'c' This is very simple and basically define specific storage entries to specific objects. I have then "container" type objects that: can be serialized similarly (in fact their are or can-be "marked") they don't serialize in their storage entries the "marked" objects (with direct reference): if a and a.b are both marked, a.save() calls b.save() and stores a.b = storage_entry(b) So, if I serialize 'a', it will serialize automatically all objects that can be reached from 'a' through the object reference graph, possibly in multiples entries. That is what I want, and is usually provides the functionalities I need. However, it is very ad-hoc and there are some structural limitations to this approach: the multi-entry saving can only works through direct connections in "container" objects, and there are situations with undefined behavior such as if two "marked" objects 'a'and 'b' both have a reference to an unmarked object 'c'. In this case my system will stores 'c' in both 'a' and 'b' making an implicit copy which not only double the storage size, but also change the object reference graph after re-loading. I am thinking of generalizing the process. Apart for the practical questions on implementation (I am coding in python, and use Pickle to serialize my objects), there is a general question on the way to attach (cluster) unmarked objects to marked ones. So, my questions are: What are the important issues that should be considered? Basically why not just use any graph parsing algorithm with the "attach to last marked node" behavior. Is there any work done on this problem, practical or theoretical, that I should be aware of? Note: I added the tag graph-database because I think the answer might come from that fields, even if the question is not.

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  • Are there any working implementations of the rolling hash function used in the Rabin-Karp string sea

    - by c14ppy
    I'm looking to use a rolling hash function so I can take hashes of n-grams of a very large string. For example: "stackoverflow", broken up into 5 grams would be: "stack", "tacko", "ackov", "ckove", "kover", "overf", "verfl", "erflo", "rflow" This is ideal for a rolling hash function because after I calculate the first n-gram hash, the following ones are relatively cheap to calculate because I simply have to drop the first letter of the first hash and add the new last letter of the second hash. I know that in general this hash function is generated as: H = c1ak - 1 + c2ak - 2 + c3ak - 3 + ... + cka0 where a is a constant and c1,...,ck are the input characters. If you follow this link on the Rabin-Karp string search algorithm , it states that "a" is usually some large prime. I want my hashes to be stored in 32 bit integers, so how large of a prime should "a" be, such that I don't overflow my integer? Does there exist an existing implementation of this hash function somewhere that I could already use? Here is an implementation I created: public class hash2 { public int prime = 101; public int hash(String text) { int hash = 0; for(int i = 0; i < text.length(); i++) { char c = text.charAt(i); hash += c * (int) (Math.pow(prime, text.length() - 1 - i)); } return hash; } public int rollHash(int previousHash, String previousText, String currentText) { char firstChar = previousText.charAt(0); char lastChar = currentText.charAt(currentText.length() - 1); int firstCharHash = firstChar * (int) (Math.pow(prime, previousText.length() - 1)); int hash = (previousHash - firstCharHash) * prime + lastChar; return hash; } public static void main(String[] args) { hash2 hashify = new hash2(); int firstHash = hashify.hash("mydog"); System.out.println(firstHash); System.out.println(hashify.hash("ydogr")); System.out.println(hashify.rollHash(firstHash, "mydog", "ydogr")); } } I'm using 101 as my prime. Does it matter if my hashes will overflow? I think this is desirable but I'm not sure. Does this seem like the right way to go about this?

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  • How to map hash keys to methods for an encapsulated Ruby class (tableless model)?

    - by user502052
    I am using Ruby on Rails 3 and I am tryng to map a hash (key, value pairs) to an encapsulated Ruby class (tableless model) making the hash key as a class method that returns the value. In the model file I have class Users::Account #< ActiveRecord::Base def initialize(attributes = {}) @id = attributes[:id] @firstname = attributes[:firstname] @lastname = attributes[:lastname] end end def self.to_model(account) JSON.parse(account) end My hash is hash = {\"id\":2,\"firstname\":\"Name_test\",\"lastname\":\"Surname_test\"} I can make account = Users::Account.to_model(hash) that returns (debugging) --- id: 2 firstname: Name_test lastname: Surname_test That works, but if I do account.id I get this error NoMethodError in Users/accountsController#new undefined method `id' for #<Hash:0x00000104cda410> I think because <Hash:0x00000104cda410> is an hash (!) and not the class itself. Also I think that doing account = Users::Account.to_model(hash) is not the right approach. What is wrong? How can I "map" those hash keys to class methods?

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  • How do I design a cryptographic hash function?

    - by Eyal
    After reading the following about why one-way hash functions are one-way, I would like to know how to design a hash function. http://stackoverflow.com/questions/1038307/help-me-better-understand-cryptographic-hash-functions/1047106#1047106 Before everyone gets on my case: Yes, I know that it's a bad idea to not use a proven and tested hash function. I would still like to know how it's done. I'm familiar with Feistel-network ciphers but those are necessarily reversible, horrible for a cryptographic hash. Is there some sort of construction that is well-used in cryptographic hashing? Something that makes it very one-way?

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  • C++ converting hexadecimal md5 hash to decimal integer

    - by Zackery
    I'm doing Elgamal Signature Scheme and I need to use the decimal hash value from the message to compute S for signature generation. string hash = md5(message); cout << hash << endl; NTL::ZZ msgHash = strtol(hash.c_str(), NULL, 16); cout << msgHash << endl; There are no integer large enough to contain the value of 32 byte hexadecimal hash, and so I tried big integer from NTL library but it didn't work out because you cannot assign long integer to NTL::ZZ type. Is there any good solution to this? I'm doing this with visual C++ in Visual Studio 2013.

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  • How to sort a hash by value in descending order and output a hash in ruby?

    - by tipsywacky
    output.sort_by {|k, v| v}.reverse and for keys h = {"a"=>1, "c"=>3, "b"=>2, "d"=>4} => {"a"=>1, "c"=>3, "b"=>2, "d"=>4} Hash[h.sort] Right now I have these two. But I'm trying to sort hash in descending order by value so that it will return => {"d"=>4, "c"=>3, "b"=>2, "a"=>1 } Thanks in advance. Edit: let me post the whole code. def count_words(str) # YOUR CODE HERE output = Hash.new(0) sentence = str.gsub(/,/, "").gsub(/'/,"").gsub(/-/, "").downcase words = sentence.split() words.each do |item| output[item] += 1 end puts Hash[output.sort_by{ |_, v| -v }] return Hash[output.sort_by{|k, v| v}.reverse] end

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  • Rails 3 : create two dimensional hash and add values from a loop

    - by John
    I have two models : class Project < ActiveRecord::Base has_many :ticket attr_accessible .... end class Ticket < ActiveRecord::Base belongs_to :project attr_accessible done_date, description, .... end In my ProjectsController I would like to create a two dimensional hash to get in one variable for one project all tickets that are done (with done_date as key and description as value). For example i would like a hash like this : What i'm looking for : @tickets_of_project = ["done_date_1" => ["a", "b", "c"], "done_date_2" => ["d", "e"]] And what i'm currently trying (in ProjectsController) ... def show # Get current project @project = Project.find(params[:id]) # Get all dones tickets for a project, order by done_date @tickets = Ticket.where(:project_id => params[:id]).where("done_date IS NOT NULL").order(:done_date) # Create a new hash @tickets_of_project = Hash.new {} # Make a loop on all tickets, and want to complete my hash @tickets.each do |ticket| # TO DO #HOW TO PUT ticket.value IN "tickets_of_project" WITH KEY = ticket.done_date ??** end end I don't know if i'm in a right way or not (maybe use .map instead of make a where query), but how can I complete and put values in hash by checking index if already exist or not ? Thanx :)

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  • parse [object XrayWrapper [object HTMLLIElement]] into HTML object

    - by kitokid
    when I access and GM_log the currentLi of li object, it is complaining undefined. So when I GM_log li value as a string , instead of HTML object, I am getting [object XrayWrapper [object HTMLLIElement]]. How can I convert it or how I can access its related elements and value ? $("#result-set li").each(function(index) { var $currentLi = $(this); var $class1link = $currentLi.find("class1"); var $class1href = $class1link.attr("href"); }

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  • Multiple Object Instantiation

    - by Ricky Baby
    I am trying to get my head around object oriented programming as it pertains to web development (more specifically PHP). I understand inheritance and abstraction etc, and know all the "buzz-words" like encapsulation and single purpose and why I should be doing all this. But my knowledge is falling short with actually creating objects that relate to the data I have in my database, creating a single object that a representative of a single entity makes sense, but what are the best practises when creating 100, 1,000 or 10,000 objects of the same type. for instance, when trying to display a list of the items, ideally I would like to be consistent with the objects I use, but where exactly should I run the query/get the data to populate the object(s) as running 10,000 queries seems wasteful. As an example, say I have a database of cats, and I want a list of all black cats, do I need to set up a FactoryObject which grabs the data needed for each cat from my database, then passes that data into each individual CatObject and returns the results in a array/object - or should I pass each CatObject it's identifier and let it populate itself in a separate query.

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  • good literature for teaching object oriented thinking in C [closed]

    - by Dipan Mehta
    Quite often C is the primary platform for the development. And when things are large scale, I have seen partitioning of the system as different objects is quite a natural thing. Some or many of the object orientated analysis and design principles are used here very well. This is not a debate question about whether or not C is a good candidate for object oriented programming or not. This is also NOT a question how to do OO in C. You can refer to this question and there are probably many such citations. As far as I am concerned, I have learned some of this things while working with many open source and commercial projects. (libjpeg, ffmpeg, Gstreamer which is based on GObject). I can probably extend a few references that explains some of these concepts such as - 1. Event Helix article, 2. Linux Mag article 3. one of my answers which links Schreiner's reference. Unfortunately, when we induct younger folks, it seems too hard to make them learn all of it the hard way. Usually, when we say it's C, a general reaction is to throw away all of the "Object thinking". Looking for help extending above references from those who have been in the similar areas of work. Are there any good formal literature that explains how Object thinking can be made to use while you are working in C? I have seen tons of book on general "object oriented paradigms" but they all focus on advanced languages mostly not in C. You see most C books - but most focus only on the syntax and the obfuscated corners of C and that's it. There are hardly ANY good reference, specially books or any systematic (I mean formal) literature on how to apply OO in C. This is very surprising given that so many large scale open source projects use C which are truly using this very well; but we hardly see any good formal literature on this subject.

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  • Console.log in IE on an object just outputted [object Object]

    - by LookitsPuck
    All, I'm used to debugging JavaScript in Chrome or Firefox just because their built in developer tools are a lot cleaner than IE's. IE8 came along way with the Developer Tools being more polished, but they're still not completely up to snuff. I like being able to step through code as if I was in Visual Studio, and that is pretty nice about IE, however, when trying to do a simple console.log on an object that I have, in Firefox/Chrome/etc. I can actually explore that object. In IE, the console is simply outputting the following: LOG: [object Object] Is there any way to drill down into that object in IE like in Chrome/Firefox/etc.? Thanks all! -Steve

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  • Difference between null==object and object==null

    - by priyank.mp
    Hi I would like to know diff between the above comparisons? I am getting null pointer exception when I check object.getItems() == null. But if I change it to null == object.getItems(), it workes fine. I did look into this http://stackoverflow.com/questions/2938476/what-is-the-difference-between-null-object-and-objectnull-closed But I didnt get satisfactory answer.

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  • bootstrap: Uncaught TypeError: Object [object Object] has no method 'tooltip', 'typeahead'

    - by DarkKnightFan
    I am trying to use the tooltip, typeahead, datepicker features of bootstrap. But I keep getting these errors in the console! Uncaught TypeError: Object [object Object] has no method 'tooltip' Uncaught TypeError: Object [object Object] has no method 'typeahead' This is how my imports look like: <link href="css/bootstrap.css" rel="stylesheet"> <link href="css/datepicker.css" rel="stylesheet"> <link href="css/bootstrap-responsive.css" rel="stylesheet"> <script type="text/javascript" src="js/jquery-1.8.0.js"></script> <script type="text/javascript" src="js/bootstrap.js"></script> <script type="text/javascript" src="js/bootstrap-datepicker.js"></script> <script type="text/javascript" src="js/bootstrap-typeahead.js"></script> <script type="text/javascript" src="js/highcharts.js"></script> <script type="text/javascript" src="js/exporting.js"></script> <link type="text/css" rel="stylesheet" href="css/jquery.dropdown.css" /> <script type="text/javascript" src="js/jquery.dropdown.js"></script> Some sample code: <a class="btn btn-success" data-toggle="modal" href="#payments" rel="tooltip" data-placement="top" title="Record your payments"> <i class="icon-check icon-white"></i> Payments</a> $("#payments").tooltip('show'); Similarly I have code for datepicker and typeahead. any solution?

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  • PHP hashing function not working properly

    - by Jordan Foreman
    So I read a quick PHP login system securing article, and was trying to sort of duplicate their hashing method, and during testing, am not getting the proper output. Here is my code: function decryptPassword($pw, $salt){ $hash = hash('sha256', $salt . hash('sha256', $pw)); return $hash; } function encryptPassword($pw){ $hash = hash('sha256', $pw); $salt = substr(md5(uniqid(rand(), true)), 0, 3); $hash = hash('sha265', $salt . $hash); return array( 'salt' => $salt, 'hash' => $hash ); } And here is my testing code: $pw = $_GET['pw']; $enc = encryptPassword($pw); $hash = $enc['hash']; $salt = $enc['salt']; echo 'Pass: ' . $pw . '<br />'; echo 'Hash: ' . $hash . '<br />'; echo 'Salt: ' . $salt . '<br />'; echo 'Decrypt: ' . decryptPassword($hash, $salt); Now, the output of this should be pretty obvious, but unfortunately, the $hash variable always comes out empty! I'm trying to figure out what the problem could be, and my only guess would be the second $hash assignment line in the encryptPassword(..) function. After a little testing, I've determined that the first assignment works smoothly, but the second does not. Any suggestions? Thanks SO!

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  • Uncaught TypeError: Property 'dist2' of object [object Object] is not a function

    - by Radu Vlad
    I have this functions that should return me the distance from point p to segment line v-w. The problem i have is after some time i receive the following error: Uncaught TypeError: Property 'dist2' of object [object Object] is not a function. I receive it in distToSegmentSquared directly,not even calling the function dist2().Is it any other dist2() anywhere in jquery?I found none... function sqr(x) { return x * x; } function dist2(v, w) { console.log(v); console.log(w); return sqr(v.x - w.x) + sqr(v.y - w.y); } function distToSegmentSquared(p, v, w) { var l2 = dist2(v, w); if (l2 == 0) return dist2(p, v); var t = ((p.x - v.x) * (w.x - v.x) + (p.y - v.y) * (w.y - v.y)) / l2; if (t < 0) return dist2(p, v); if (t > 1) return dist2(p, w); return dist2(p, {x: v.x + t * (w.x - v.x), y: v.y + t * (w.y - v.y)}); } function distToSegment(p, v, w) { return Math.sqrt(distToSegmentSquared(p, v, w)); } The values that are given in for that error are: p: Object x: 461 y: 333 v: Object x: 80 y: 120 w: Object x: 260 y: 120

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  • PHP Object References in Frameworks

    - by bigstylee
    Before I dive into the disscusion part a quick question; Is there a method to determine if a variable is a reference to another variable/object? For example $foo = 'Hello World'; $bar = &$foo; echo (is_reference($bar) ? 'Is reference' : 'Is orginal'; I have been using PHP5 for a few years now (personal use only) and I would say I am moderately reversed on the topic of Object Orientated implementation. However the concept of Model View Controller Framework is fairly new to me. I have looked a number of tutorials and looked at some of the open source frameworks (mainly CodeIgnitor) to get a better understanding how everything fits together. I am starting to appreciate the real benefits of using this type of structure. I am used to implementing object referencing in the following technique. class Foo{ public $var = 'Hello World!'; } class Bar{ public function __construct(){ global $Foo; echo $Foo->var; } } $Foo = new Foo; $Bar = new Bar; I was surprised to see that CodeIgnitor and Yii pass referencs of objects and can be accessed via the following method: $this->load->view('argument') The immediate advantage I can see is a lot less code and more user friendly. But I do wonder if it is more efficient as these frameworks are presumably optimised? Or simply to make the code more user friendly? This was an interesting article Do not use PHP references.

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  • Use a subclass object to modify a protected propety within its superclass object

    - by gadmeer
    Sorry for the crappy title I failed to think of a better version for my Java question. I am right now using Java version: 1.6.0_18 and Netbeans version: 6.8 Now for the question. What I've done is created a class with only one protected int property and next I made a public method to Set the int property to a given value. Then I made an object of that class and used said public method to set the int property to 5. Now I need your help to create another class that will take said object and expose it's protected int property. The way I could think of doing this was to create a sub class to inherit said class and then create a method to Get the int property of the super class. I kind of succeeded to create the code to Get the int property but now I can't figure out how to use this new sub class to reference the object of the super class. Here are the 2 classes I have thus far: public class A { protected int iNumber; public void setNumber ( int aNumber ) { iNumber = aNumber; } } public class B extends A { public int getNumber() { return super.iNumber; } } I created an object of 'A' and used its method to set its property to 5, like this: A objA = new A(); objA.setNumber ( 5 ); Now I want to create an object of 'B' to output the int stored within the property of 'objA'. I've tried to run this code: B objB = (B) objA; String aNumber_String = String.valueOf( objB.getNumber() ); System.out.println( aNumber_String ); but I got the error: "java.lang.ClassCastException" on the first line B objB = (B) objA; Please is there anyway of doing what I am trying to do? P.S. I am hoping to make this idea work because I do not want to edit class A (unless I have no choice) by giving it a getter method. P.P.S Also I know it's a 'bad' idea to expose the property instead of making it private and use public setter / getter methods but I like it this way :). Edit: Added code tags

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  • VB.NET - Object reference not set to an instance of an object

    - by Daniel
    I need some help with my program. I get this error when I run my VB.NET program with a custom DayView control. ***** Exception Text ******* System.NullReferenceException: Object reference not set to an instance of an object. at SeaCow.Main.DayView1_ResolveAppointments(Object sender, ResolveAppointmentsEventArgs args) in C:\Users\Daniel\My Programs\Visual Basic\SeaCow\SeaCow\SeaCow\Main.vb:line 120 at Calendar.DayView.OnResolveAppointments(ResolveAppointmentsEventArgs args) at Calendar.DayView.OnPaint(PaintEventArgs e) at System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer) at System.Windows.Forms.Control.WmPaint(Message& m) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) According to the error code, the 'for each' loop below is causing the NullReferenceException error. At default, the 'appointments' list is assigned to nothing and I can't find where the ResolveAppointments function is being called at. Private Sub DayView1_ResolveAppointments(ByVal sender As Object, ByVal args As Calendar.ResolveAppointmentsEventArgs) Handles DayView1.ResolveAppointments Dim m_Apps As New List(Of Calendar.Appointment) For Each m_App As Calendar.Appointment In appointments If (m_App.StartDate >= args.StartDate) AndAlso (m_App.StartDate <= args.EndDate) Then m_Apps.Add(m_App) End If Next args.Appointments = m_Apps End Sub Anyone have any suggestions?

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  • Removing duplicates without overriding hash method

    - by Javi
    Hello, I have a List which contains a list of objects and I want to remove from this list all the elements which have the same values in two of their attributes. I had though about doing something like this: List<Class1> myList; .... Set<Class1> mySet = new HashSet<Class1>(); mySet.addAll(myList); and overriding hash method in Class1 so it returns a number which depends only in the attributes I want to consider. The problem is that I need to do a different filtering in another part of the application so I can't override hash method in this way (I would need two different hash methods). What's the most efficient way of doing this filtering without overriding hash method? Thanks

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