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  • Is incrementing in a loop exponential time?

    - by user356106
    I've a simple but confusing doubt about whether the program below runs in exponential time. The question is : given a +ve integer as input, print it out. The catch is that you deliberately do this in a loop, like this: int input,output=0; cininput; while(input--) ++output; // Takes time proportional to the value of input cout<< output; I'm claiming that this problem runs in exponential time. Because, the moment you increase the # of bits in input by 1, the program takes double the amount of time to execute. Put another way, to print out log2(input) bits, it takes O(input) time. Is this reasoning right?

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  • What do you find wrong or strange in this Perl code to simulate objects without bless?

    - by user350571
    I'm new to Perl and its blessing stuff to imitate class like functionality made me feel strange I even had to go to the bathroom. Now, please tell me: what do you don't like, find wrong or strange with this code: sub Person { my $age = shift || 15; return { printAge => sub { print "Age -> $age\n"; }, changeAge => sub { $age = shift } } } my $p = Person(); my $p2 = Person(27); $p->{printAge}->(); $p->{changeAge}->(30); $p->{printAge}->(); $p2->{printAge}->();

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  • Getting the final value to this MySQL query...

    - by Jack W-H
    I've got my database set up with three tables - code, tags, and code_tags for tagging posts. This will be the SQL query processed when a post is submitted. Each tag is sliced up by PHP and individually inserted using these queries. INSERT IGNORE INTO tags (tag) VALUES ('$tags[1]'); SELECT tags.id FROM tags WHERE tag = '$tags[1]' ORDER BY id DESC LIMIT 1; INSERT INTO code_tags (code_id, tag_id) VALUES ($codeid, WHAT_GOES_HERE?) The WHAT_GOES_HERE? value at the end is what I need to know. It needs to be the ID of the tag that the second query fetched. How can I put that ID into the third query? I hope I explained that correctly. I'll rephrase if necessary.

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  • Can I change class types in a setter with an object-oriented language?

    - by user214626
    Hello, Here is the problem statement : Calling a setter on the object should result in the object to change to an object of a different class, which language can support this ? Ex. I have a class called "Man" (Parent Class), and two children namely "Toddler" and "Old Man", they are its children because they override a behaviour in Man called as walk.( i.e Toddler sometimes walks using both his hands and legs kneeled down and the Old man uses a stick to support himself). The Man class has a attribute called age, I have a setter on Man,say it is called setAge(int ageValue). I have 3 objects, 2 toddlers, 1 old-Man. (The system is up and running,i guess when we say objects it is obvious) .I will make this call, toddler.setAge(80), I expect the toddler to change to an object of type Old Man. Is this possible.Please suggest. Thanks,

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  • Saving an IP adddress to DB

    - by Mark
    I want to save a user's IP address to my database just in case any legal issues come up and we need to track down who performed what action. Since I highly doubt I will ever actually need to use this data (well, maybe for counting unique hits or something) do you think I can just dump the REMOTE_ADDR into a field? If so, what should the length of that field be? 39 chars should fit an IPv6 address, no? I don't know if I'll ever get any of those, but just in case...

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  • .Net - Whats the difference between a Session Facade and Business Delegate?

    - by KP65
    What I understand so far: Business Delegate - In the presentation tier, as an ASP component, provides an interface for ASP views to access business components without exposing their API, therefore reducing coupling between the two. Session Facade - In the business tier, as a com+ component, encapsulates business objects, provides a course grain interface for views to access business components. Reduces coupling, hides complex business component interaction from views. So what is the actual difference? They seem pretty similar to me..

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  • Brilliant features of C++

    - by John
    (Following Features to remove from C++ and Desired features for C++, I thought why not complete the trio...) What C++ features would you not change? What features are elegantly and brilliantly implemented and still look better than other popular languages?

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  • Regarding the ViewModel

    - by mizipzor
    Im struggling to understand the ViewModel part of the MVVM pattern. My current approach is to have a class, with no logic whatsoever (important), except that it implements INotifyPropertyChanged. The class is just a collection of properties, a struct if you like, describing an as small part of the data as possible. I consider this my Model. Most of the WPF code I write are settings dialogs that configure said Model. The code-behind of the dialog exposes a property which returns an instance of the Model. In the XAML code I bind to subproperties of that property, thereby binding directly to the Model's properties. Which works quite well since it implements the INotifyPropertyChanged. I consider this settings dialog the View. However, I havent really been able to figure out what in all this is the ViewModel. The articles Ive read suggests that the ViewModel should tie the View and the Model together, providing the logic the Model lacks but is still to complex to go directly into the View. Is this correct? Would, in my example, the code-behind of the settings dialog be considered the ViewModel? I just feel a bit lost and would like my peers to debunk some of my assumptions. Am I completely off track here?

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  • C++ game designing & polymorphism question

    - by Kotti
    Hi! I'm trying to implement some sort of 'just-for-me' game engine and the problem's plot goes the following way: Suppose I have some abstract interface for a renderable entity, e.g. IRenderable. And it's declared the following way: interface IRenderable { // (...) // Suppose that Backend is some abstract backend used // for rendering, and it's implementation is not important virtual void Render(Backend& backend) = 0; }; What I'm doing right now is something like declaring different classes like class Ball : public IRenderable { virtual void Render(Backend& backend) { // Rendering implementation, that is specific for // the Ball object // (...) } }; And then everything looks fine. I can easily do something like std::vector<IRenderable*> items, push some items like new Ball() in this vector and then make a call similiar to foreach (IRenderable* in items) { item->Render(backend); } Ok, I guess it is the 'polymorphic' way, but what if I want to have different types of objects in my game and an ability to manipulate their state, where every object can be manipulated via it's own interface? I could do something like struct GameState { Ball ball; Bonus bonus; // (...) }; and then easily change objects state via their own methods, like ball.Move(...) or bonus.Activate(...), where Move(...) is specific for only Ball and Activate(...) - for only Bonus instances. But in this case I lose the opportunity to write foreach IRenderable* simply because I store these balls and bonuses as instances of their derived, not base classes. And in this case the rendering procedure turns into a mess like ball.Render(backend); bonus.Render(backend); // (...) and it is bad because we actually lose our polymorphism this way (no actual need for making Render function virtual, etc. The other approach means invoking downcasting via dynamic_cast or something with typeid to determine the type of object you want to manipulate and this looks even worse to me and this also breaks this 'polymorphic' idea. So, my question is - is there some kind of (probably) alternative approach to what I want to do or can my current pattern be somehow modified so that I would actually store IRenderable* for my game objects (so that I can invoke virtual Render method on each of them) while preserving the ability to easily change the state of these objects? Maybe I'm doing something absolutely wrong from the beginning, if so, please point it out :) Thanks in advance!

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  • Problem with IE 6 page loading.

    - by Puneet Dudeja
    I have a website which works fine in all browsers except in IE6. The pages content is inside a div loaded with a background image. The page layout gets very nasty and image does not load when the page is opened for first time, but when the same page is opened for the second time and any subsequent times, then it loads perfectly. This scenario is with every page in the site. Please help.

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  • How would you code an efficient Circular Buffer in Java or C#

    - by Cheeso
    I want a simple class that implements a fixed-size circular buffer. It should be efficient, easy on the eyes, generically typed. EDIT: It need not be MT-capable, for now. I can always add a lock later, it won't be high-concurrency in any case. Methods should be: .Add and I guess .List, where I retrieve all the entries. On second thought, Retrieval I think should be done via an indexer. At any moment I will want to be able to retrieve any element in the buffer by index. But keep in mind that from one moment to the next Element[n] may be different, as the Circular buffer fills up and rolls over. This isn't a stack, it's a circular buffer. Regarding "overflow": I would expect internally there would be an array holding the items, and over time the head and tail of the buffer will rotate around that fixed array. But that should be invisible from the user. There should be no externally-detectable "overflow" event or behavior. This is not a school assignment - it is most commonly going to be used for a MRU cache or a fixed-size transaction or event log.

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  • Correct handling of return data

    - by Serhiy
    Hello, I have a question related to correct handling of returns of the DAO library I'm writing for one project. This library probably is going to be used by another people and I want to do it correctly. So I would like to know, how I should deal with return statements of the functions of my DAO. Example 1 I have function to getCustomer which should return String. In case query doesn't return any result should I return null, empty string or throw some kind of Exception? Example 2 I have function getCutomerList which return ArrayList. In case query doesn't return any result should I return null, empty ArrayList or throw some Exception? Example 3 Some sql exception was detected, what should I do: throw exception or do try..catch of the block where it can occur? What is the "good" practice or "best" practice to apply in my case? Thanks on advance, Serhiy.

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  • Need some clarification on the ANSI/SPARC 3-tier database architecture.

    - by Moonshield
    Hi there, I'm currently revising for a databases exam and looking over some past papers, but there's one question that I'm slightly unsure about and was wondering if someone could offer some assistance. "Describe EACH of the THREE levels of the ANSI SPARC 3 level architecture. Your answer should include the purpose of EACH of the schemas, the level of abstraction they provide and the software tools that would be used to access and support them." As I understand it (although please correct me if I'm wrong): the internal schema specifies the physical storage of the data; the conceptual schema specifies the structure of the database and the domains; and the external schemas are how the database is viewed by "users" (applications, etc.). As for the abstraction, I understand that the conceptual layer means that the physical data storage can be altered without the end user being affected, likewise the The bit that I'm not sure about is what tools are used to access and support each layer. Would the internal schema be handled by the DBMS, the conceptual schema handled by some sort of DDL interpreter and the external schema handled by a DML interpreter (or have I misunderstood what each level does)? Any assistance would be greatly appreciated. Thanks, Moonshield

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  • Converting ASP.NET MVC to n-Tiered Architecture

    - by Jeff
    I just built an application using ASP.NET MVC. The programmers at my company want to build all future modules using n-Tiered (Presentation Layer, Business Logic Layer, Data Access Layer) architecture. I am not the programmer and need to know why this makes sense? Do I have to completely rewrite the entire code or can it be converted? We are building an HRIS system with Business Intelligence. Somebody please explain why or why not this approach does or does not make sense.

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  • wpf command pattern

    - by evan
    I have a wpf gui which displays a list of information in separate window and in a separate thread from the main application. As the user performs actions in the main window the side window is updated. (For example if you clicked page down in the main window a listbox in the side window would page down). Right now the architecture for this application feels very messy and I'm sure there is a cleaner way to do it. It looks like this: Main Window contains a singleton SideWindowControl which communicates with an instance of the SideWindowDisplay using events - so, for example, the pagedown button would work like: 1) the event handler of the button on the main window calls SideWindowControl.PageDown() 2) in the PageDown() function a event is created and thrown. 3) finally the gui, ShowSideWindowDisplay is subscribing to the SideWindowControl.Actions event handles the event and actually scrolls the listbox down - note because it is in a different thread it has to do that by running the command via Dispatcher.Invoke() This just seems like a very messy way to this and there must be a clearer way (The only part that can't change is that the main window and the side window must be on different threads). Perhaps using WPF commands? I'd really appreciate any suggestions!! Thanks

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  • What information do you capture when your software crashes in the field?

    - by Russ
    I am working on rewriting my unexpected error handling process, and I would like to ask the community: What information do you capture both automatic, and manually, when software you have written crashes? Right now, I capture a few items, some of which are: Automatic: Name of app that crashed Version of app that crashed Stack trace Operating System version RAM used by the application Number of processors Screen shot: (Only on non-public applications) User name and contact information (from Active Directory) Manual: What context is the user in (i.e.: what company, tech support call number, RA number, etc...) When did the user expect to happen? (Typical response: "Not to crash”) Steps to reproduce. What other bits of information do you capture that helps you discover the true cause of an applications problem, especially given that most users simply mash the keyboard when asked to tell you what happened. For the record I’m using C#, WPF and .NET version 4, but I don’t necessarily want to limit myself to those. Related: http://stackoverflow.com/questions/1226671/what-to-collect-information-when-software-crashes Related: http://stackoverflow.com/questions/701596/what-should-be-included-in-the-state-of-the-art-error-and-exception-handling-stra

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  • Managing libraries and imports in a programming language

    - by sub
    I've created an interpreter for a stupid programming language in C++ and the whole core structure is finished (Tokenizer, Parser, Interpreter including Symbol tables, core functions, etc.). Now I have a problem with creating and managing the function libraries for this interpreter (I'll explain what I mean with that later) So currently my core function handler is horrible: // Simplified version myLangResult SystemFunction( name, argc, argv ) { if ( name == "print" ) { if( argc < 1 ) { Error('blah'); } cout << argv[ 0 ]; } else if ( name == "input" ) { if( argc < 1 ) { Error('blah'); } string res; getline( cin, res ); SetVariable( argv[ 0 ], res ); } else if ( name == "exit ) { exit( 0 ); } And now think of each else if being 10 times more complicated and there being 25 more system functions. Unmaintainable, feels horrible, is horrible. So I thought: How to create some sort of libraries that contain all the functions and if they are imported initialize themselves and add their functions to the symbol table of the running interpreter. However this is the point where I don't really know how to go on. What I wanted to achieve is that there is e.g.: an (extern?) string library for my language, e.g.: string, and it is imported from within a program in that language, example: import string myString = "abcde" print string.at( myString, 2 ) # output: c My problems: How to separate the function libs from the core interpreter and load them? How to get all their functions into a list and add it to the symbol table when needed? What I was thinking to do: At the start of the interpreter, as all libraries are compiled with it, every single function calls something like RegisterFunction( string namespace, myLangResult (*functionPtr) ); which adds itself to a list. When import X is then called from within the language, the list built with RegisterFunction is then added to the symbol table. Disadvantages that spring to mind: All libraries are directly in the interpreter core, size grows and it will definitely slow it down.

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  • Are bad data issues that common?

    - by Water Cooler v2
    I've worked for clients that had a large number of distinct, small to mid-sized projects, each interacting with each other via properly defined interfaces to share data, but not reading and writing to the same database. Each had their own separate database, their own cache, their own file servers/system that they had dedicated access to, and so they never caused any problems. One of these clients is a mobile content vendor, so they're lucky in a way that they do not have to face the same problems that everyday business applications do. They can create all those separate compartments where their components happily live in isolation of the others. However, for many business applications, this is not possible. I've worked with a few clients, one of whose applications I am doing the production support for, where there are "bad data issues" on an hourly basis. Yeah, it's that crazy. Some data records from one of the instances (lower than production, of course) would have been run a couple of weeks ago, and caused some other user's data to get corrupted. And then, a data script will have to be written to fix this issue. And I've seen this happening so much with this client that I have to ask. I've seen this happening at a moderate rate with other clients, but this one just seems to be out of order. If you're working with business applications that share a large amount of data by reading and writing to/from the same database, are "bad data issues" that common in your environment?

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  • Unit Testing User Interface. What is an effective way ?

    - by pierocampanelli
    I have an accounting & payroll client/server application where there are several input form with complex data validation rules. I am finding an effective way to perform unit testing of user interface. For complex validation rules I mean: "Disable button X if I Insert a value in textfield Y" "Enable a combobox if I insert a value in a textfield" ...... ...... Most promising pattern i have found is suggested by M. Fowler (http://martinfowler.com/eaaDev/ModelViewPresenter.html). Have you any experience about Unit Testing of User Interface? As technology stack I am using: .NET 3.5 & Windows Forms Widget Library.

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  • What's a good icon to represent a legend or a key for a diagram?

    - by Bears will eat you
    I'm implementing a small web app widget that shows a legend/key for a diagram (or chart/map/graph/whatever), but only during mouseover of the widget. It's basically just going to be a div with a background image. What would be a good icon that communicates "I show the legend" or "I am the legend" to the unfamiliar users? I'm looking for something in the 10x10 to 20x20 pixel range. Assuming that a legend is the same thing as a key (is it?) then I could use a small icon of a key (like you'd unlock a door with) but that seems cheesy or unclear at worst. I'm not sure that's really the clearest way to do it. Is there an icon that should instantly remind users of a legend?

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  • Database schema for Product Properties

    - by Chemosh
    As so many people I'm looking for a Products /Product Properties database schema. I'm using Ruby on Rails and (Thinking) Sphinx for faceted searches. Requirements: Adding new product types and their options should not require a change to the database schema Support faceted searches using Sphinx. Solutions I've come across: (See Bill Karwin's answer) Option 1: Single Table Inheritance Not an option really. The table would contain way to many columns. Option 2: Class Table Inheritance Ruby on Rails caches the database schema on start-up which means a restart whenever a new type of product is introduced. If you have a size able product catalog this could mean hundreds of tables. Option 3: Serialized LOB Kills being able to do faceted searches without heavy application logic. Option 4: Entity-Attribute-Value For testing purposes, EAV worked fine. However it could quickly become a mess and a maintenance hell as you add more and more options (e.g. when an option increase the prices or delivery time). What option should I go with? What other solutions are out there? Is there a silver bullet (ha) I overlooked?

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