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  • What is an overloaded operator in c++?

    - by Jeff
    I realize this is a basic question but I have searched online, been to cplusplus.com, read through my book, and I can't seem to grasp the concept of overloaded operators. A specific example from cplusplus.com is: // vectors: overloading operators example #include <iostream> using namespace std; class CVector { public: int x,y; CVector () {}; CVector (int,int); CVector operator + (CVector); }; CVector::CVector (int a, int b) { x = a; y = b; } CVector CVector::operator+ (CVector param) { CVector temp; temp.x = x + param.x; temp.y = y + param.y; return (temp); } int main () { CVector a (3,1); CVector b (1,2); CVector c; c = a + b; cout << c.x << "," << c.y; return 0; } from http://www.cplusplus.com/doc/tutorial/classes2/ but reading through it I'm still not understanding them at all. I just need a basic example of the point of the overloaded operator (which I assume is the "CVector CVector::operator+ (CVector param)"). There's also this example from wikipedia: Time operator+(const Time& lhs, const Time& rhs) { Time temp = lhs; temp.seconds += rhs.seconds; if (temp.seconds >= 60) { temp.seconds -= 60; temp.minutes++; } temp.minutes += rhs.minutes; if (temp.minutes >= 60) { temp.minutes -= 60; temp.hours++; } temp.hours += rhs.hours; return temp; } from "http://en.wikipedia.org/wiki/Operator_overloading" The current assignment I'm working on I need to overload a ++ and a -- operator. Thanks in advance for the information and sorry about the somewhat vague question, unfortunately I'm just not sure on it at all.

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  • Javascript permission denied. Not cross domain?

    - by Dan
    I'm working on a web app that very rarely returns a Javacript permission denied error when attempting to access document elements. I'm well aware of cross-domain issues and I am actively pursuing them as a possible cause. My question is: are there other possible causes for a permission denied exception? Just want to make sure I'm looking in to all possible avenues. Thanks!

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  • Finding the maximum weight subsequence of an array of positive integers?

    - by BeeBand
    I'm tring to find the maximum weight subsequence of an array of positive integers - the catch is that no adjacent members are allowed in the final subsequence. The exact same question was asked here, and a recursive solution was given by MarkusQ. He provides an explanation, but can anyone help me understand how he has expanded the function? How does this solution take into consideration non-adjacent members?

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  • Convolve a column vector

    - by Geoff
    This is an OpenCV2 question. I have a matrix: cv::Mat_<Point3f> points; representing some space curve. I want to smooth it (using, for example a Gaussian kernel). I have tried using: cv::Mat_<Point3f> result; cv::GaussianBlur(points, result, cv::Size(4 * sigma, 1), sigma, sigma, cv::BORDER_WRAP); But I get the error: Assertion failed (columnBorderType != BORDER_WRAP)

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  • Sending an int array through Winsocks

    - by seed
    I'm trying to send an int array through Winsocks. I might be wrong, but I'm pretty sure only a char* is supported so I'm kind of stuck on how to do this properly. There are also problems with little/big edian, so what would be a good way to do this? I've already asked a question of converting int array to char but it was recommended to start a new thread on this in the networking section instead.

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  • How can i resolve the N+1 Selects problem ?

    - by Maxime ARNSTAMM
    Hello everyone, I have trouble understanding how to avoid the n+1 select in jpa or hibernate. From what i read, there's the 'left join fetch', but i'm not sure if it still works with more than one list (oneToMany).. Could someone explain it to me, or give me a link with a clear complete explanation please ? I'm sorry if this is a noob question, but i can't find a real clear article or doc on this issue. Thanks

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  • python command line yes/no input

    - by h3
    Is there any short way to achieve what APT does in Python ? I mean, when the package manager prompts a yes/no question followed by "[Yes/no]". The scripts accepts YES/Y/yes/y or "enter" (defaults to Yes as hinted by the capital) The only thing I find in the official doc is input/raw_input.. I know it's not that hard to emulate, but it's annoying to rewrite :|

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  • Powerbuilder "runtime"

    - by dariopy
    I've copied (not installed) a system developed with Powerbuilder, from a salvaged hard drive. I want to run the application, but of course, it asks for several DLLs and stuff like that, which are not registered in my current system. My question: is there a procedure to install a "powerbuilder runtime", so to say, in order to run the application?

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  • MySQL - Calculating fields on the fly vs storing calculated data

    - by Christian Varga
    Hi Everyone, I apologise if this has been asked before, but I can't seem to find an answer to a question that I have about calculating on the fly vs storing fields in a database. I read a few articles that suggested it was preferable to calculate when you can, but I would just like to know if that still applies to the following 2 examples. Example 1. Say you are storing data relating to a car. You store the fuel tank size in litres, and how many litres it uses per 100km. You also want to know how many KMs it can travel, which can be calculated from the tank size and economy. I see 2 ways of doing this: When a car is added or updated, calculate the amount of KMs and store this as a static field in the database. Every time a car is accessed, calculate the amount of KMs on the fly. Because the cars economy/tank size doesn't change (although it could be edited), the KMs is a pretty static value. I don't see why we would calculate it every single time the car is accessed. Wouldn't this waste cpu time as opposed to simply storing it in a separate field in the database and calculating only when a car is added or updated? My next example, which is almost an entirely different question (but on the same topic), relates to counting children. Let's say we have a app which has categories and items. We have a view where we display all the categories, and a count of all the items inside each category. Again, I'm wondering what's better. To perform a MySQL query to count all the items in each category every single time the page is accessed? Or store the count in a field in the categories table and update when an item is added / deleted? I know it is redundant to store anything that can be calculated, but I worry that calculating fields or counting records might be slow as opposed to storing the data in a field. If it's not then please let me know, I just want to learn about when to use either method. On a small scale I guess it wouldn't matter either way, but apps like Facebook, would they really count the amount of friends you have every time someone views your profile or would they just store it as a field? I'd appreciate any responses to both of these scenarios, and any resource that might explain the benefits of calculating vs storing. Thanks in advance, Christian

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  • Microsoft C++ Language Reference

    - by eSKay
    Whenever any question is asked, and a reference text is needed, I never see MSDN C++ Language Reference being referred. I was browsing through it and I personally feel that it is extremely well written. Is there some specific reason it is not used as often as a standard? Is it because it contains some VC++ specific features?

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  • Getting the Position of an Android phone by using GPS

    - by poeschlorn
    Hey, it's me again, I've got another question regarding to basic Android programming: How can I access the GPS for getting the current Position of the mobile phone the app is running on? How long can this take to retrieve the information? In this case the GPS might be disabled, how can I enable/disable it again. Which permissions must be granted in the andorid manifest? Greetings and thanks for ur answers, poeschlorn

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  • Is a Multi-DAL Approach the way to go here?

    - by Krisc
    Working on the data access / model layer in this little MVC2 project and trying to think things out to future projects. I have a database with some basic tables and I have classes in the model layer that represent them. I obviously need something to connect the two. The easiest is to provide some sort of 'provider' that can run operations on the database and return objects. But this is for a website that would potentially be used "a lot" (I know, very general) so I want to cache results from the data layer and keep the cache updated as new data is generated. This question deals with how best to approach this problem of dual DALS. One that returns cached data when possible and goes to the data layer when there is a cache miss. But more importantly, how to integrate the core provider (thing that goes into database) with the caching layer so that it too can rely on cached objects rather than creating new ones. Right now I have the following interfaces: IDataProvider is used to reach the database. It doesn't concern itself with the meaning of the objects it produces, but simply the way to produce them. interface IDataProvider{ // Select, Update, Create, et cetera access IEnumerable<Entry> GetEntries(); Entry GetEntryById(int id); } IDataManager is a layer that sits on top of the IDataProvider layer and manages the cache interface IDataManager : IDataProvider{ void ClearCache(); } Note that in practice the IDataManager implementation will have useful helper functions to add objects to their related cache stores. (In the future I may define other functions on the interface) I guess what I am looking for is the best way to approach a loop back from the IDataProvider implementations so that they can access the cache. Or a different approach entirely may be in order? I am not very interested in 3rd party products at the moment as I am interested in the design of these things much more than this specific implementation. Edit: I realize the title may be a bit misleading. I apologize for that... not sure what to call this question.

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  • How to make a nested query with an Entity that doesn't really exist (many-to-many)

    - by Calou
    Hi everyone, I'm new with Doctrine2 so my question can be easy to answer (I hope so). First of all, here the SQL query that I'd want : SELECT * FROM Document WHERE id NOT IN (SELECT document_id FROM Documents_Folders) Pretty simple isn't it ? The porblem is that my table 'Documents_Folders' is not an entity. In fact, it was create because I have a many-to-many relation between my entities 'Document' and 'Folder'. I tried several queries, but none worked. Thanks.

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  • How Can I Programmatically Build a Multi-Page TIFF out of Many Single Page TIFFs, Using Python?

    - by MetaHyperBolic
    I've found, via Google, numerous people asking the same question, but no solutions. The Python Image Library (PIL) has tools for stepping through an already existing multi-page TIFF, but nothing about creating them. Libraries would hopefully be available on Windows, for Python 2.6. If there's some freeware out there which will do the trick, I wouldn't mind seeing it, but I was hoping I could accomplish this in Python.

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  • Best openid implementation

    - by AyKarsi
    I think OpenId has many things for it. But the biggest beef I have with it, is usability. Especially the technically non-savvy have dificulty understanding that the need to select a "provider" to login. Stackoverflows login implementation is quite good, but I think it would cost me quite some explaining to get my mother to use here gmail account to register/login to another site... So the question is: Does anynone know OpenId register/login implemtantions which are more usable than Stackoverflows?

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  • Running Rails as an embedded app inside of a gem

    - by randombits
    I'm trying to understand what exactly the above (in my question's Title) means? This is taken directly from the SpreeCommerce.com project: If you’re an experienced Rails developer you may be wondering where your app directory is. Spree actually runs as an embedded Rails app inside of your gem. How do you customize things then? We’ll cover that later in extensions. Source: http://spreecommerce.com/documentation/getting_started.html Can someone further explain what exactly it means when a Rails app is run "inside of your gem"

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  • Good design of mapping Java Domain objects to Tables (using Hibernate)

    - by M. McKenzie
    Hey guys, I have a question that is more in the realm of design, than implementation. I'm also happy for anyone to point out resources for the answer and I'll gladly, research for myself. Highly simplified Java and SQL: Say I have a business domain POJO called 'Picture' with three attributes. class Picture int idPicture String fileName long size Say I have another business domain POJO called "Item" with 3 attributes Class Item int idItem String itemName ArrayList itemPictures These would be a normal simple relationship. You could say that 'Picture' object, will never exist outside an 'Item' object. Assume a picture belongs only to a specific item, but that an item can have multiple pictures Now - using good database design (3rd Normal Form), we know that we should put items and pictures in their own tables. Here is what I assume would be correct. table Item int idItem (primary key) String itemName table Picture int idPicture (primary key) varchar(45) fileName long size int idItem (foreign key) Here is my question: If you are making Hibernate mapping files for these objects. In the data design, your Picture table needs a column to refer to the Item, so that a foreign key relation can be maintained. However,in your business domain objects - your Picture does not hold a reference/attribute to the idItem - and does not need to know it. A java Picture instance is always instantiated inside an Item instance. If you want to know the Item that the Picture belongs to you are already in the correct scope. Call myItem.getIdItem() and myItem.getItemPictures(),and you have the two pieces of information you need. I know that Hibernate tools have a generator that can auto make your POJO's from looking at your database. My problem stems from the fact that I planned out the data design for this experiment/project first. Then when I went to make the domain java objects, I realized that good design dictated that the objects hold other objects in a nested way. This is obviously different from the way that a database schema is - where all objects(tables) are flat and hold no other complex types within them. What is a good way to reconcile this? Would you: (A) Make the hibernate mapping files so that Picture.hbm.xml has a mapping to the POJO parent's idItem Field (if it's even possible) (B) Add an int attribute in the Picture class to refer to the idItem and set it at instantiation, thus simplifying the hbm.xml mapping file by having all table fields as local attributes in the class (C) Fix the database design because it is wrong, dork. I'd truly appreciate any feedback

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  • How do I create a Django ModelForm, so that it's fields are sometimes required, sometimes not?

    - by Graf
    Ok, here is the question. Imagine I have a ModelForm which have only two fields. like this one: class ColorForm(forms.Form): color_by_name = forms.CharField() color = forms.IntegerField(widget = forms.Select(choices=COLOR_CHOICES)) So a user can either input a color name, a choose it from a list. Color is required, but that doesn't mean, that user should enter it manually. There do I put validation, so that my code checks if user selected color in dropdownlist and if not then he should write it manually?

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  • When, if ever, is "number of lines of code" a useful metric?

    - by user15071
    Some people claim that code's worst enemy is its size, and I tend to agree. Yet every day you keep hearing things like I write blah lines of code in a day. I own x lines of code. Windows is x million lines of code. Question: When is "#lines of code" useful? ps: Note that when such statements are made, the tone is "more is better".

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  • How to unit test private methods in BDD / TDD?

    - by robert_d
    I am trying to program according to Behavior Driven Development, which states that no line of code should be written without writing failing unit test first. My question is, how to use BDD with private methods? How can I unit test private methods? Is there better solution than: - making private methods public first and then making them private when I write public method that uses those private methods; or - in C# making all private methods internal and using InternalsVisibleTo attribute. Robert

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  • C++ priority queue structure used ?

    - by John Retallack
    While searching for some functions in C++ STL documentation I read that push and pop for priority queues needs constant time. "Constant (in the priority_queue). Although notice that push_heap operates in logarithmic time." My question is what kind of data structure is used to mantain a priority queue with O(1) for push and pop ?

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  • How can I progrommatically change the target framework from 4.0 to 3.5 of a project/solution?

    - by scott
    Edit 3: After more googling it looks like you can't have the TargetFrameworkMoniker property in a .NET 3.5 application. So I guess I should be asking a different question. How do I change the Target framework from 4.0 to 3.5? Unfortunately, I can only find stuff on how to go the other way. or better yet how do i progrommatically set the target framework version of a project to something other than 4.0? Original question: I just switched to vs2010. I have an application that uses .net 3.5. It loads plugins which are generated by a different app. The plugins are using .net 4 and there for cannot be loaded. I'm using EnvDTE.Project to create a project and set the settings. I can't find what setting needs to be set for this. Edit 1: I'm generating code for about 50 solutions. When I made the switch from vs2005 to vs2010 the projects in those solutions are defaulting to .NET Framework 4.0. So I need to set the .NET Framework to 3.5 when I am generating the code for these solutions. Edit 2: After a lot of googling I found this. so then I tried this: loProp = vsGetProperty("TargetFrameworkMoniker"); vsSetValue(loProp, ".NETFramework,Version=v3.5"); the definitions for those two methods are below. as far as I can tell they do the same this as project.Properties.Item("TargetFrameworkMoniker").Value = ".NETFramework,Version=v4.0,Profile=Client"; I start getting an Property Unavailable Exception later in the code. When I remove the new lines everything works except the projects target framework is still 4.0. The code generators target framework is 3.5 so I can't use the FrameworkName class like shown in the second example in that link. here is vsGetProperty protected Property vsGetProperty(string aProperty) { bool lbDone = false; int liCount = 0; Property loProp; while (!lbDone && liCount < pMaxRetries) { try { loProp = pProject.Properties.Item(aProperty); lbDone = true; return loProp; } catch (System.Runtime.InteropServices.COMException loE) { liCount++; if ((uint)loE.ErrorCode == 0x80010001) { // RPC_E_CALL_REJECTED - sleep half sec then try again System.Threading.Thread.Sleep(pDelayBetweenRetry); } } } return null; } and vsSetValue protected void vsSetValue(Property aProperty, string aValue) { bool lbDone = false; int liCount = 0; while (!lbDone && liCount < pMaxRetries) { try { aProperty.Value = aValue; lbDone = true; } catch (System.Runtime.InteropServices.COMException loE) { liCount++; if ((uint)loE.ErrorCode == 0x80010001) { // RPC_E_CALL_REJECTED - sleep half sec then try again System.Threading.Thread.Sleep(pDelayBetweenRetry); } } } }

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