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  • Impossible to use ref and out in Extension methods?

    - by Hun1Ahpu
    Why is it forbidden to call Extension method with ref modifier? This one is possible: public static void Change(ref TestClass testClass, TestClass testClass2) { testClass = testClass2; } And this one not: public static void ChangeWithExtensionMethod(this ref TestClass testClass, TestClass testClass2) { testClass = testClass2; } But why?

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  • Are programming languages and methods inefficient? (assembler and C knowledge needed)

    - by b-gen-jack-o-neill
    Hi, for a long time, I am thinking and studying output of C language compiler in assembler form, as well as CPU architecture. I know this may be silly to you, but it seems to me that something is very ineffective. Please, don´t be angry if I am wrong, and there is some reason I do not see for all these principles. I will be very glad if you tell me why is it designed this way. I actually truly believe I am wrong, I know the genius minds of people which get PCs together knew a reason to do so. What exactly, do you ask? I´ll tell you right away, I use C as a example: 1: Stack local scope memory allocation: So, typical local memory allocation uses stack. Just copy esp to ebp and than allocate all the memory via ebp. OK, I would understand this if you explicitly need allocate RAM by default stack values, but if I do understand it correctly, modern OS use paging as a translation layer between application and physical RAM, when address you desire is further translated before reaching actual RAM byte. So why don´t just say 0x00000000 is int a,0x00000004 is int b and so? And access them just by mov 0x00000000,#10? Because you wont actually access memory blocks 0x00000000 and 0x00000004 but those your OS set the paging tables to. Actually, since memory allocation by ebp and esp use indirect addressing, "my" way would be even faster. 2: Variable allocation duplicity: When you run application, Loader load its code into RAM. When you create variable, or string, compiler generates code that pushes these values on the top o stack when created in main. So there is actual instruction for do so, and that actual number in memory. So, there are 2 entries of the same value in RAM. One in form of instruction, second in form of actual bytes in the RAM. But why? Why not to just when declaring variable count at which memory block it would be, than when used, just insert this memory location?

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  • extension methods with generics - when does caller need to include type parameters?

    - by Greg
    Hi, Is there a rule for knowing when one has to pass the generic type parameters in the client code when calling an extension method? So for example in the Program class why can I (a) not pass type parameters for top.AddNode(node), but where as later for the (b) top.AddRelationship line I have to pass them? class Program { static void Main(string[] args) { // Create Graph var top = new TopologyImp<string>(); // Add Node var node = new StringNode(); node.Name = "asdf"; var node2 = new StringNode(); node2.Name = "test child"; top.AddNode(node); top.AddNode(node2); top.AddRelationship<string, RelationshipsImp>(node,node2); // *** HERE *** } } public static class TopologyExtns { public static void AddNode<T>(this ITopology<T> topIf, INode<T> node) { topIf.Nodes.Add(node.Key, node); } public static INode<T> FindNode<T>(this ITopology<T> topIf, T searchKey) { return topIf.Nodes[searchKey]; } public static void AddRelationship<T,R>(this ITopology<T> topIf, INode<T> parentNode, INode<T> childNode) where R : IRelationship<T>, new() { var rel = new R(); rel.Child = childNode; rel.Parent = parentNode; } } public class TopologyImp<T> : ITopology<T> { public Dictionary<T, INode<T>> Nodes { get; set; } public TopologyImp() { Nodes = new Dictionary<T, INode<T>>(); } }

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  • What are Class methods in Python for?

    - by Dave Webb
    I'm teaching myself Python and my most recent lesson was that Python is not Java, and so I've just spent a while turning all my Class methods into functions. I now realise that I don't need to use Class methods for what I would done with static methods in Java, but now I'm not sure when I would use them. All the advice I can find about Python Class methods is along the lines of newbies like me should steer clear of them, and the standard documentation is at its most opaque when discussing them. Does anyone have a good example of using a Class method in Python or at least can someone tell me when Class methods can be sensibly used?

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  • Should I be using abstract methods in this Python scenario?

    - by sfjedi
    I'm not sure my approach is good design and I'm hoping I can get a tip. I'm thinking somewhere along the lines of an abstract method, but in this case I want the method to be optional. This is how I'm doing it now... from pymel.core import * class A(object): def __init__(self, *args, **kwargs): if callable(self.createDrivers): self._drivers = self.createDrivers(*args, **kwargs) select(self._drivers) class B(A): def createDrivers(self, *args, **kwargs): c1 = circle(sweep=270)[0] c2 = circle(sweep=180)[0] return c1, c2 b = B() In the above example, I'm just creating 2 circle arcs in PyMEL for Maya, but I fully intend on creating more subclasses that may or may not have a createDrivers method at all! So I want it to be optional and I'm wondering if my approach is—well, if my approach could be improved?

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  • Can you have an extension method on a type instead of on an instance of a type?

    - by SLC
    I can have an extension method like this: DateTime d = new DateTime(); d = d.GetRandomDate(); GetRandomDate is my extension method. However the above doesn't make much sense. What would be better is: DateTime d = DateTime.GetRandomDate(); However, I don't know how to do this. An extension method created as: public static DateTime GetRandomDate(this System.DateTime dt) will only add the GetRandomDate() in the first example above, not the second one. Is there a way to achieve the desired behaviour?

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  • In scala can I pass repeated parameters to other methods?

    - by Fred Haslam
    Here is something I can do in java, take the results of a repeated parameter and pass it to another method: public void foo(String ... args){bar(args);} public void bar(String ... args){System.out.println("count="+args.length);} In scala it would look like this: def foo(args:String*) = bar(args) def bar(args:String*) = println("count="+args.length) But this won't compile, the bar signature expects a series of individual strings, and the args passed in is some non-string structure. For now I'm just passing around arrays. It would be very nice to use starred parameters. Is there some way to do it?

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  • Are programming languages and methods ineffective? (assembler and C knowledge needed)

    - by b-gen-jack-o-neill
    Hi, for a long time, I am thinking and studying output of C language compiler in asemlber form, as well as CPU architecture. I know this may be silly to you, but it seems to me that something is very ineffective. Please, don´t be angry if I am wrong, and there is some reason I do not see for all these principles. I will be very glad if you tell me why is it designed this way. I actually trully believe I am wrong, I know the genius minds of people which get PCs together knew a reason to do so. What exactly, do you ask? I´ll tell you right away, I use C as a example: 1, Stack local scope memory allocation: So, typical local memory allocation uses stack. Just copy esp to ebp and than allocate all the memory via ebp. OK, I would understand this if you explicitly need allocate RAM by default stack values, but if I do understand it correctly, modern OS use paging as a translation layer between application and physical RAM, when adress you desire is further translated before reaching actuall RAM byte. So why don´t just say 0x00000000 is int a,0x00000004 is int b and so? And access them just by mov 0x00000000,#10? Becouse you wont actually access memory blocks 0x00000000 and 0x00000004 but those your OS set the paging tables to. Actually, since memory allocation by ebp and esp use indirect adressing, "my" way would be even faster. 2, Variable allocation duplicitly: When you run aaplication, Loader load its code into RAM. When you create variable, or string, compiler generates code that pushes these values on the top o stack when created in main. So there is actuall instruction for do so, and that actuall number in memory. So, there are 2 entries of the same value in RAM. One in fomr of instruction, second in form of actuall bytes in the RAM. But why? Why not to just when declaring variable count at which memory block it would be, than when used, just insert this memory location?

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  • When should methods be made private?

    - by AaronSzy
    There are lots of times where i'm not sure whether a particular method should be made private or not. For example, i'm building a class right now, which, is responsible for generating a report. This class has a buildReport method and several methods which collect the necessary data for buildReport. // single public method // uses a set of helper methods public buildReport() // helper methods private avgSurveyTime() private fetchVendors() private fetchSendCounts() private ... Im debating whether i should make these helper methods public. The only method i really plan on calling outside at the moment is buildReport. However, it might be useful to get just a list of the vendors with fetchVendors etc. I see two schools of thought on this: You can always expose as little as possible. (In which case, many of my classes would only have one public method) OR you can expose all you can that might be useful to the user of the class. Is there a good rule of thumb to use for deciding when methods should be made public/private?

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  • Online betting system design [closed]

    - by Rafal
    I am a Computer Science student, preparing for my exam in software engineering. I am strugging with answering one of the sample questions to the scenario below. My understanding is that the system design approach should probably be a mixture of agile and plan driven elements but - since I've no practical experience - it's hard for me to decide on the balance and tolls that should be used. I will appreciate any hints from experienced business analysts who were involved in similar kind of projects. Ray Sing is the owner of “Last Betz", a bookmakers with 7 outlets across Louth and Meath. With the advent of smartphones Ray would now like to allow his clients to place their bets online using their mobile devices. Clients would register for an account and password and would log their credit card details via the Last Betz website. To begin using the facility customers must 'load' their accounts with 100 euros. Any winnings, minus commission, will be placed in the account whilst any losses will be automatically deducted from the account. Assuming you have been selected to develop the above system: How would you approach the design of this system? Discuss the design methods and models you would use.

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  • javadoc and overloaded methods

    - by skrebbel
    Hi all, I'm developing an API with many identically named methods that just differ by signature, which I guess is fairly common. They all do the same thing, except that they initialize various values by defaults if the user does not want to specify. As a digestible example, consider public interface Forest { public Tree addTree(); public Tree addTree(int amountOfLeaves); public Tree addTree(int amountOfLeaves, Fruit fruitType); public Tree addTree(int amountOfLeaves, int height); public Tree addTree(int amountOfLeaves, Fruit fruitType, int height); } The essential action performed by all of these methods is the same; a tree is planted in the forest. Many important things users of my API need to know about adding trees hold for all these methods. Ideally, I would like to write one Javadoc block that is used by all methods: /** * Plants a new tree in the forest. Please note that it may take * up to 30 years for the tree to be fully grown. * * @param amountOfLeaves desired amount of leaves. Actual amount of * leaves at maturity may differ by up to 10%. * @param fruitType the desired type of fruit to be grown. No warranties * are given with respect to flavour. * @param height desired hight in centimeters. Actual hight may differ by * up to 15%. */ In my imagination, a tool could magically choose which of the @params apply to each of the methods, and thus generate good docs for all methods at once. With Javadoc, if I understand it correctly, all I can do is essentially copy&paste the same javadoc block five times, with only a slightly differing parameter list for each method. This sounds cumbersome to me, and is also difficult to maintain. Is there any way around that? Some extension to javadoc that has this kind of support? Or is there a good reason why this is not supported that I missed?

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  • Unit test complex classes with many private methods

    - by Simon G
    Hi, I've got a class with one public method and many private methods which are run depending on what parameter are passed to the public method so my code looks something like: public class SomeComplexClass { IRepository _repository; public SomeComplexClass() this(new Repository()) { } public SomeComplexClass(IRepository repository) { _repository = repository; } public List<int> SomeComplexCalcualation(int option) { var list = new List<int>(); if (option == 1) list = CalculateOptionOne(); else if (option == 2) list = CalculateOptionTwo(); else if (option == 3) list = CalculateOptionThree(); else if (option == 4) list = CalculateOptionFour(); else if (option == 5) list = CalculateOptionFive(); return list; } private List<int> CalculateOptionOne() { // Some calculation } private List<int> CalculateOptionTwo() { // Some calculation } private List<int> CalculateOptionThree() { // Some calculation } private List<int> CalculateOptionFour() { // Some calculation } private List<int> CalculateOptionFive() { // Some calculation } } I've thought of a few ways to test this class but all of them seem overly complex or expose the methods more than I would like. The options so far are: Set all the private methods to internal and use [assembly: InternalsVisibleTo()] Separate out all the private methods into a separate class and create an interface. Make all the methods virtual and in my tests create a new class that inherits from this class and override the methods. Are there any other options for testing the above class that would be better that what I've listed? If you would pick one of the ones I've listed can you explain why? Thanks

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  • UIWebView: webViewDidStartLoad/webViewDidFinishLoad delegate methods not called when loading certain URLs

    - by Dia
    I have basic web browser implemented using a UIWebView. I've noticed that for some pages, none of the UIWebViewDelegate methods are called. An example page in which this happens is: http://www.youtube.com/user/google. Here are the steps to reproduce the issue (make sure you insert NSLog calls in your controller's UIWebViewDelegate methods): Load the above youtube URL into the UIWebView [notice that here, the UIWebViewDelegate methods do get called when the page loads] Touch the "Uploads" category on the page Touch any video in that category [issue: notice that a new page is loaded, but none of the UIWebView delegates are called] I know that this is not an issue of UIWebView's delegate not being set properly, since the delegate methods do get invoked when loading other links (e.g. if you try clicking on a link that takes you outside of youtube, you'll notice the delegate methods getting called). My gut feeling initially was that it might be because the page is loaded using AJAX, which may not invoke the delegate method. But then when I checked Safari, it did not exhibit this problem, so it must be something on my side. I've also noticed that Three20's TTWebController has the exact same issue as I'm having. But the problem that arises from this issue is that without the delegate methods called, I'm unable to update the UI to enable/disable the back and forward browsing buttons when new requests are loaded. And idea why this is happening or how can I work around it to update the UI when a new request is made?

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  • What to call factory-like (java) methods used with immutable objects

    - by StaxMan
    When creating classes for "immutable objects" immutable meaning that state of instances can not be changed; all fields assigned in constructor) in Java (and similar languages), it is sometimes useful to still allow creation of modified instances. That is, using an instance as base, and creating a new instance that differs by just one property value; other values coming from the base instance. To give a simple example, one could have class like: public class Circle { final double x, y; // location final double radius; public Circle(double x, double y, double r) { this.x = x; this.y = y; this.r = r; } // method for creating a new instance, moved in x-axis by specified amount public Circle withOffset(double deltaX) { return new Circle(x+deltaX, y, radius); } } So: what should method "withOffset" be called? (note: NOT what its name ought to be -- but what is this class of methods called). Technically it is kind of a factory method, but somehow that does not seem quite right to me, since often factories are just given basic properties (and are either static methods, or are not members of the result type but factory type). So I am guessing there should be a better term for such methods. Since these methods can be used to implement "fluent interface", maybe they could be "fluent factory methods"? Better suggestions? EDIT: as suggested by one of answers, java.math.BigDecimal is a good example with its 'add', 'subtract' (etc) methods. Also: I noticed that there's this question (by Jon Skeet no less) that is sort of related (although it asks about specific name for method)

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  • How to connect to local instance of SQL Server 2008 Express

    - by Billy Logan
    I just installed SQL Server 2008 Express on my windows 7 machine. I previously had 2005 on here and used it just fine with the old SQL Server Management Studio Express. I was able to connect with no problems to my PC-NAME\SQLEXPRESS instance. I uninstalled 2005 and SQL Server Management Studio Express. I then installed SQL Server 2008 Express on my machine and elected to have it install SQL Server Management Studio. Now, when I try to connect to PC-NAME\SQLEXPRESS (with Windows Authentication, like I always did), I get the following message: Cannot connect to PC-NAME\SQLEXPRESS. A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified) (Microsoft SQL Server, Error: -1) For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&EvtSrc=MSSQLServer&EvtID=-1&LinkId=20476 When I went to the help link it mentions, the help page suggests the following: * Make sure that the SQL Server Browser service is started on the server. * Use the SQL Server Surface Area Configuration tool to enable SQL Server to accept remote connections. For more information about the SQL Server Surface Area Configuration Tool, see Surface Area Configuration for Services and Connections. I did try starting the SQL Server Browser, but don't see that the Surface Area Configuration is installed with this express version. I had seen another user with an almost exact same issue that was missing the database engine on install. If that were the case how could i test for that and where would i go to download that install. Thanks in advance, Billy

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  • Amazon EC2 instance was not available for few minutes (amazon showed that everything ok)

    - by Salvador Dali
    Few minutes ago my amazon Ec2 instance was unavailable for a few minutes. During this time neither I was able to connect to web-site with http, nor I was able to ssh to it. Also I was not able to connect to my amazon management console for some time (less than amount of unavailability of my instance). When I was able to connect to management console, it was showing me that everything is running smoothly (but I still was not able to connect to instance in any way for a minute or two). During this time I have checked their status page just to see that there is no issues (my instance is in Ireland and there is nothing wrong there today). After that I was able to log in. I checked my logins with last to see that no one except me was logging in. I also looked in apache logs and there was no errors or warnings during this time. Right now when I see my amazon monitor, I see a small spike in CPU in last 15 minutes (but this is from 10% to like 20%) I have no idea what can it be (I have never experienced anything like this before) and therefore I have no idea how scared should I be or what else should I look for. Can anyone give me a hint what my actions should be in such situation?

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  • Mounting an Amazon EC2 instance on MAC OS X

    - by hinghoo
    What are some methods for transferring files to and from Amazon EC2 instances. I'm looking for solutions / tools for editing files as well as copying files to EC2 instances from both Mac and Windows. For example, what are some solutions for mounting a drive from an instance locally? Generally, what other methods are out there?

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  • IIS 7: launch unique site instance per host name

    - by OlduwanSteve
    Is it possible to configure IIS 7 so that a single site with multiple bindings (or wildcard bindings) will launch a unique instance for each unique host name? To explain why this is desirable, we have an application that retrieves its configuration from a remote system. The behaviour of the application is governed by this configuration and not by the 'web.config'. The application uses its host name as a key to retrieve the configuration. Currently it is a manual process to create an identical IIS site for each instance of the application, differing only by the bindings. My thought, if it were possible, is that it would be nice to have one IIS site that effectively works as a template for an arbitrary number of dynamic sites. Whenever it is accessed by a unique host name a new instance of the site would be launched, and all further requests to that host name would go to that instance just as though I had created the site by hand. I use IIS regularly, but only for fairly straightforward site hosting. I'd like to know if this could be configured with vanilla IIS 7, but would also welcome answers that require a plugin or 3rd party product. Programming/architectural suggestions about changes to the app wouldn't really be appropriate for serverfault.

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  • SQLBrowser will not start

    - by Oliver
    SQL Server 2005 x64 on Windows Server 2003 x64, with multiple instances (default + 2 named). Engineers moved server to a different domain. Since then, cannot get SQLBrowser to start. Still able to query the default instance, and can access named instances by port (TCP:hostname,port#). When on server, can use SSMS to connect to the instances, all is well from that perspective. No errors in the SQL Server logs. As SQLBrowser is starting, an entry in EventViewer.Application says that one of the named instances has an invalid configuration, but I haven't been able to figure out what is invalid. Startup continues, and next message says "The SQLBrowser service was unable to establish SQL instance and connectivity discovery." Next, it enables instance and connectivity discovery support; next, another message about that same named instance having an invalid configuration; then an event says that SQLBrowser has started; last, an event shows the SQLBrowser service has shutdown. I got SQLBrowser to get past the issue with the first named instance by temporarily renaming a registry entry, and now the second named instance can be accessed by name rather than port. Still, cannot access the first named instance by name. Advice?

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  • Read Linux-formatted (ext3) EBS volume mounted on Windows Server 2008 instance

    - by Greg Owen
    I've got a Windows Server 2008 R2 instance set up in Amazon EC2. I've also got some Ubuntu instances on the same EC2 account. I'd like to be able to mount the EBS volume from one of the Ubuntu instances onto the Windows instance as an external drive and then access that drive from the Windows instance. I've looked at tools like ext2fsd and ext2 IFS, but these haven't worked (I couldn't get the former to work, and the latter says that it supports Windows 2008 but gives an error when I try to install it, saying that it only supports up to Windows 2003). I know that there are all kinds of tools to view Linux partitions and that there are filesystems that are compatible with both Linux and Windows, but neither of those options works here (I want to be able to attach and detach the Ubuntu volumes on command, rather than have a permanent partition, and Ubuntu EBS volumes are ext3 by default). Anybody know a good tool I should use?

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  • MSSQL instance shuts down

    - by citronas
    I'm currently developing a new ASP.net project hosted on a Windows Server 2008 RC2 with an MSSQL 2008 Express Database. I have three SQL instances (for different purposes) running which currently all contain a single database. For apprently no reason, these instances tend to shut down after some days, for no apparent reason. There might be low or none traffic to these instances, because there might be some days in a row, where I can't develop. It now occured several times, that one or two of these three instances just shut down, so that I can't access the database, without manually starting the instance. I can't seem to find a event log entry for the shutdown, which is most likely because I just enabled logging (why is the default setting off?) So the questions are: * Why does a SQL instance shut down? (Is there such thing as a "Shut down instance after 3 days of inactivity"? * How can I achieve that the instances are running 24/7?

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  • Installing a new SQL Server instance fails

    - by Rubio
    I've previously in my setup installed SQL Server Express 2005. Now I've switched to SQL Server Express 2008. I updated the command line parameters to those documented for the latter. If the comp already has SQL Server Express 2008 installed, my installer should create a new instance. The command line parameters are as follows: /ACTION=Install /FEATURES=SQLEngine /QS /INSTANCENAME=ABCD /SECURITYMODE=SQL /SAPWD=CunningPassword The requested instance name does not exist on the target machine. This will end in an error -2068643838. The logs show the following error: "No features were installed during the setup execution. The requested features may already be installed." If I remove the /QS parameter and try to install interactively, I'll get as far as the Feature Selection page. The UI shows three options, Instance Features, Shared Features and Redistributable Features. Whatever I select, clicking Next results in the same error (There are validation errors on this page). Any ideas anyone? Thanks, -- Rubio

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