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  • How do I manipulate a tree of immutable objects?

    - by Frederik
    I'm building an entire application out of immutable objects so that multi-threading and undo become easier to implement. I'm using the Google Collections Library which provides immutable versions of Map, List, and Set. My application model looks like a tree: Scene is a top-level object that contains a reference to a root Node. Each Node can contain child Nodes and Ports. An object graph might look like this: Scene | +-- Node | +-- Node | +- Port +-- Node | +- Port +- Port If all of these objects are immutable, controlled by a top-level SceneController object: What is the best way to construct this hierarchy? How would I replace an object that is arbitrarily deep in the object tree? Is there a way to support back-links, e.g. a Node having a "parent" attribute?

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  • switch easily between different main()

    - by lezebulon
    I'm using VS2010 I have a project with several headers and one file with the main() function. For testing purposes I'd like to be able to easily another main() function that would instanciate different things than my original main. Is there an easy way to define 2 "main" function, and easily switch between them? The best would be to compile 2 binaries, one that starts at main1() and the other at main2(), or it can be a solution that requires to recompile some files, it doesn't matter

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  • How to handle ids and polymorphic associations in views if compound keys are not supported?

    - by duncan
    I have a Movie plan table: movie_plans (id, description) Each plan has items, which describe a sequence of movies and the duration in minutes: movie_plan_items (id, movie_plan_id, movie_id, start_minutes, end_minutes) A specific instance of that plan happens in: movie_schedules (id, movie_plan_id, start_at) However the schedule items can be calculated from the movie_plan_items and the schedule start time by adding the minutes create view movie_schedule_items as select CONCAT(p.id, '-', s.id) as id, s.id as movie_schedule_id, p.id as movie_plan_item_id, p.movie_id, p.movie_plan_id, (s.start_at + INTERVAL p.start_minutes MINUTE) as start_at, (s.start_at + INTERVAL p.end_minutes MINUTE) as end_at from movie_plan_items p, movie_schedules s where s.movie_plan_id=p.movie_plan_id; I have a model over this view (readonly), it works ok, except that the id is right now a string. I now want to add a polymorphic property (like comments) to various of the previous tables. Therefore for movie_schedule_items I need a unique and persistent numeric id. I have the following dilemma: I could avoid the id and have movie_schedule_items just use the movie_plan_id and movie_schedule_id as a compound key, as it should. But Rails sucks in this regard. I could create an id using String#hash or a md5, thus making it slower or collision prone (and IIRC String#hash is no longer persistent across processes in Ruby 1.9) Any ideas on how to handle this situation?

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  • VS2010 + IE8 Debugging woes - Element not found

    - by Chin
    I am having great difficulty trying to debug with vs2010 and IE8, though I think the problem is more IE8 specific. When starting a debug session 9 times out of 10 I will have the following problem. IE tab says connecting.. - then after a 5 second wait I will get an error in VS saying element not found. Even when I click ok to dismiss the error, the IE window still shows connecting... I will then have to kill the IE process to be able to close IE to try again. Sometimes however I am lucky and it starts. But the whole thing is so random I have no clue where to start. One thing I have noticed is that I always have 2 IE processes started even though there is only one window open. One has a small footprint of 100k, I presume it is some kind of helper. I am using a static port with the built in WebDev server. If anyone has had similar problems please let me know how you resolved it. Its driving me nuts! thanks

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  • Alternative to singleton for unique resources

    - by user1320881
    I keep reading over and over again that one should avoid using singletons for various reasons. I'm wondering how to correctly handle a situation where a class represents a unique system resource. For example, a AudioOutput class using SDL. Since SDL_OpenAudio can only be open once at a time it makes no sense having more then one object of this type and it seems to me preventing accidentally making more then one object would actually be good. Just wondering what experienced programmers think about this, am i missing another option ?

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  • How listview delete data in database

    - by Bud33
    I have a problem to delete data in listview, I was able to delete data in listview select record, but data which selected is not deleted in the database, I have a source code Private _updateinputalltrans As Boolean Private Sub btndelete_Click(sender As System.Object, e As System.EventArgs) Handles btndelete.Click With Me.listviewpos.SelectedItem .Remove() End With MessageBox.Show("Are you sure delete this record?", "Confirmation", MessageBoxButtons.YesNo, MessageBoxIcon.Exclamation, New EventHandler(AddressOf DeleteData)) End Sub Private Sub DeleteData(ByVal sender As Object, ByVal e As EventArgs) Dim conn As New Connection(Connectiondb) If Me.updateinputalltrans = False Then If Me.listviewpos.Items.Count > 0 Then For Each del As ListViewItem In listviewpos.Items conn.delete_dtpospart(del.Text) Next End If End If End Sub delete_dtpospart a declare which connection to the database using a stored procedure

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  • DDD: Where to create entity objects?

    - by ciscoheat
    I have three entities that must interact: User, SupportTicketand PhoneConversation. When someone calls in requesting help, the User should have a SupportTicket assigned to him, with a PhoneConversation assigned to the Ticked describing the call. My question is: In what entity should I put the method CreatePhoneSupportTicket() that creates a new SupportTicket and a PhoneConversation, relates them to each other and finally relates the SupportTicket to the User? I'm guessing it can't be on the user because that would violate the SRP (the user does a few more things). But the method itself does more than one thing, it should create both a SupportTicket and a PhoneConversation. Is this a situation when a Service is a better solution then putting methods on entities? Thanks for your help!

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  • Problem understanding Inheritance

    - by dhruvbird
    I've been racking my brains over inheritance for a while now, but am still not completely able to get around it. For example, the other day I was thinking about relating an Infallible Human and a Fallible Human. Let's first define the two: Infallible Human: A human that can never make a mistake. It's do_task() method will never throw an exception Fallible Human: A human that will occasionally make a mistakes. It's do_task() method may occasionally throw a ErrorProcessingRequest Exception The question was: IS an infallible human A fallible human OR IS a fallible human AN infallible human? The very nice answer I received was in the form of a question (I love these since it gives me rules to answer future questions I may have). "Can you pass an infallible human where a fallible human is expected OR can you pass a fallible human where an infallible human is expected?" It seems apparent that you can pass an infallible human where a fallible human is expected, but not the other way around. I guess that answered my question. However, it still feels funny saying "An infallible human is a fallible human". Does anyone else feel queasy when they say it? It almost feels as if speaking out inheritance trees is like reading out statements from propositional calculus in plain English (the if/then implication connectives don't mean the same as that in spoken English). Does anyone else feel the same?

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  • How can I achieve this kind of relationship (inheritance, composition, something else)?

    - by Tim
    I would like to set up a foundation of classes for an application, two of which are person and student. A person may or may not be a student and a student is always a person. The fact that a student “is a” person led me to try inheritance, but I can't see how to make it work in the case where I have a DAO that returns an instance of person and I then want to determine if that person is a student and call student related methods for it. class Person { private $_firstName; public function isStudent() { // figure out if this person is a student return true; // (or false) } } class Student extends Person { private $_gpa; public function getGpa() { // do something to retrieve this student's gpa return 4.0; // (or whatever it is) } } class SomeDaoThatReturnsPersonInstances { public function find() { return new Person(); } } $myPerson = SomeDaoThatReturnsPersonInstances::find(); if($myPerson->isStudent()) { echo 'My person\'s GPA is: ', $myPerson->getGpa(); } This obviously doesn't work, but what is the best way to achieve this effect? Composition doesn't sond right in my mind because a person does not “have a” student. I'm not looking for a solution necessarily but maybe just a term or phrase to search for. Since I'm not really sure what to call what I'm trying to do, I haven't had much luck. Thank you!

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  • What are provenly scalable data persistence solutions for consumer profiles?

    - by Hubbard
    Consumer profiles with analytical scores [ConsumerID, 1..n demographical variables, 1...n analytical scores e.g. "likely to churn" "likely to buy an item 100$ in worth" etc.] have to be possible to query fast if they are to be used in customizing web-sites, consumer communications etc. Well. If you have: Large number of consumers Large profiles with a huge set of variables (as profiles describing human behaviour are likely to be..) ...you are in trouble. If you really have a physical relational database to which you target a query and then a physical disk starts to rotate someplace to give you an individual profile or a set of profiles, the profile user (a web site customizing a page, a recommendation engine making a recommendation..) has died of boredom before getting any observable results. There is the possibility of having the profiles in memory, which would of course increase the performance hugely. What are the most proven solutions for a fast-response, scalable consumer profile storage? Is there a shootout of these someplace?

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  • Global variable in a recursive function how to keep it at zero?

    - by Grammin
    So if I have a recursive function with a global variable var_: int var_; void foo() { if(var_ == 3) return; else var_++; foo(); } and then I have a function that calls foo() so: void bar() { foo(); return; } what is the best way to set var_ =0 everytime foo is called thats not from within itself. I know I could just do: void bar() { var_ =0; foo(); return; } but I'm using the recursive function a lot and I don't want to call foo and forget to set var_=0 at a later date. Does anyone have any suggestions on how to solve this? Thanks, Josh

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  • Have 2 separate tables or an additional field in 1 table?

    - by hkansal
    Hello, I am making a small personal application regarding my trade of shares of various companies. The actions can be selling shares of a company or buying. Therefore, the details to be saved in both cases would be: Number of Shares Average Price Would it be better to use a separate tables for "buy" and "sell" or just use one table for "trade" and keep a field that demarcates "buy" from "sell"?

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  • How do you specify a 64 bit unsigned int const 0x8000000000000000 in VS2008?

    - by Mark Franjione
    I read about the Microsoft specific suffix "i64" for integer constants. I want to do an UNsigned shift to a ULONGLONG. ULONGLONG bigNum64 = 0x800000000000000i64 >> myval; In normal C, I would use the suffix "U", e.g. the similar 32 bit operation would be ULONG bigNum32 = 0x80000000U >> myval; I do NOT want the 2's complement sign extension to propogate through the high bits. I want an UNSIGNED shift on a 64 bit const number. I think my first statement is going to do a SIGNED shift right. I tried 0x800000000000000i64U and 0x800000000000000u64 but got compiler errors.

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  • What's the steps for SQL optimization and changes without reflect live system ?

    - by Space Cracker
    we have a big portal that build using SharePoint 2007 , asp.net 3.5 , SQL Server 2005 .. many developers work in it since 01/2008 and we are now doing huge analysis for current SQL Databases [not share-point DB ] to optimize and enhance it. The main db have about 330 table and 1720 stored procedure (SP) created from 01/2008 till now Many table names / Columns is very long and we want to short it we found SP names is written in 25 format :( , some of them are very complex and also we want to rename many SP parameters need to be renamed one of the biggest table is Registered user table, that will be spitted in more than one table for some optimization, many columns name will be changed I searched for the way that i can rename table names ,columns and i found SQL refactor tool but i still trying it .. my questions : Is SQl Refactor is the best tool for renaming ? or is there any other one ? if i want to make it manually, is there any references or best practice for that ? How can i do such changes in fast and stable way .. i search for recommendations and case studies if exist ?

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  • Localizing formatting functions instead of properties in VS.NET resources

    - by LexL
    I noticed that .NET framework uses formatting functions, generated the same way localizable string are. There is a resource file Resources.resx with resource string TestString. So you may use it in code like this: string localizableValue = Resources.TestString; Now, imagine you need a formattable localizable string, to use it in string.Format function. So everytime you use it, you have to write something like this: string localizableFormattedValue = string.Format(Resources.TestFormatString, someParam1, someParam2); The observation says that in .NET framework generated resource classes already include the above construction. So instead of string property, a string function is generated. The resulting code looks like this: string localizableFormattedValue = Resources.TestFormatString(someParam1, someParam2); The question is - how do they do this? Is it some custom Microsoft feature (resx generator) or I'm missing something obvious?

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  • How to write this in better way?

    - by dario
    Hi all. Let's look at this code: IList<IHouseAnnouncement> list = new List<IHouseAnnouncement>(); var table = adapter.GetData(); //get data from repository object -> DataTable if (table.Rows.Count >= 1) { for (int i = 0; i < table.Rows.Count-1; i++) { var anno = new HouseAnnouncement(); anno.Area = float.Parse(table.Rows[i][table.powierzchniaColumn].ToString()); anno.City = table.Rows[i][table.miastoColumn].ToString(); list.Add(anno); } } return list; Is it better way to write this in less code and better fashion (must be :-) )? Maybe using labda (but let mi know how)? Thanks in advance!

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  • Publish/Subscribe paradigm: Why must message classes not know about their subscribers?

    - by carleeto
    From Wikipedia: "Publish/subscribe (or pub/sub) is a messaging paradigm where senders (publishers) of messages are not programmed to send their messages to specific receivers (subscribers). Rather, published messages are characterized into classes, without knowledge of what (if any) subscribers there may be" I can understand why a sender must not be programmed to send its message to a specific receiver. But why must published messages be classes that do not have knowledge of their subscribers? It would seem that once the messaging system itself is in place, what typically changes as software evolves is the messages sent, the publishers and the receivers. Keeping the messages separate from the subscribers seems to imply that the subscription model might also change. Is this the reason? Also, does this occur in the real world? I realize this may be a basic question, but I'm trying to understand this paradigm and your replies are very much appreciated.

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  • how to run if(!User.IsAuthenticated) or access Profile.values in App_Code? c# .NET

    - by korben
    i'm trying to run a conditional statement in a class i'm placing in my App_Code folder the condition is whether the person is logged in or not. I normally have two ways to do this in my masterpage and ASPX's if (!User.IsAuthenticated) or if(Profile.username = "anonymous") however neither of these things seem available to me in the .cs i'm making. anyone know what i'm missing? maybe a using namespace up top?

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  • does anyone see any issues with this thread pattern?

    - by prmatta
    Here is a simple thread pattern that I use when writing a class that needs just one thread, and needs to a specific task. The usual requirements for such a class are that it should be startable, stopable and restartable. Does anyone see any issues with this pattern that I use? public class MyThread implements Runnable { private boolean _exit = false; private Thread _thread = null; public void start () { if (_thread == null) { _thread = new Thread(this, "MyThread"); _thread.start(); } } public void run () { while (_exit) { //do something } } public void stop () { _exit = true; if (_thread != null) { _thread.interrupt(); _thread = null; } } } I am looking for comments around if I am missing something, or if there is a better way to write this.

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  • Python: How should I make instance variables available?

    - by swisstony
    Suppose I have: class myclass: def __init__(self): self.foo = "bar" where the value of foo needs to be available to users of myclass. Is it OK to just read the value of foo directly from an instance of myclass? Should I add a get_foo method to myclass or perhaps add a foo property? What's the best practice here?

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  • Project Reference added to one of the projects in the same solution appears broken in another solution

    - by CSharpLearner
    I have couple of solutions. In the first solution I have many projects. One of the project named 'A' has a project reference of another project 'B' of the same solution. In second solution, the project 'A' is added but not the project 'B'. Both the solutions build successfully. However, in second solution, reference of B added in the project A, appears broken. Why? Now, in first solution, instead of adding Project reference of B into A, i simply add a 'file reference' of B's DLL (which is copied at the common output directory created for all the projects) into A. Now the reference appears broken in both the solution even though both the solutions are built successfully. May I know what should I do when I have such a scenario?

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  • Linking Error Building 64bit Qt app on 32bit XP machine.

    - by photo_tom
    I'm trying to build a 64 bit version of my application (and yes I really do need the memory) on my 32bit xp dev box for production testing on our Vista64 server. Previously, I have built w/o any errors the Qt 4.6.2 DLL's in 64 bit mode. That step went vary smooth. Just to get started in building production, I'm trying to rebuild Qt's Star Delegate demo in 64bit mode. I converted the 32bit to 64bit app by changing the application configuration and adjusting the library's to the 64bit venisons. Now, when I go to link, I'm getting the following error when I link 1>------ Build started: Project: stardelegate, Configuration: Release x64 ------ 1>Linking... 1>MSVCRT.lib(crtexew.obj) : error LNK2001: unresolved external symbol WinMain 1>release64\stardelegate.exe : fatal error LNK1120: 1 unresolved externals Suggestions? edit - After some more searching, discovered if I link as a console app it will work and run. But not as a windows app. And I don't have this problem in 32 bit mode.

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