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  • Circular dependency with generics

    - by devoured elysium
    I have defined the following interface: public interface IStateSpace<State, Action> where State : IState where Action : IAction<State, Action> // <-- this is the line that bothers me { void SetValueAt(State state, Action action); Action GetValueAt(State state); } Basically, an IStateSpace interface should be something like a chess board, and in each position of the chess board you have a set of possible movements to do. Those movements here are called IActions. I have defined this interface this way so I can accommodate for different implementations: I can then define concrete classes that implement 2D matrix, 3D matrix, graphs, etc. public interface IAction<State, Action> { IStateSpace<State, Action> StateSpace { get; } } An IAction, would be to move up(this is, if in (2, 2) move to (2, 1)), move down, etc. Now, I'll want that each action has access to a StateSpace so it can do some checking logic. Is this implementation correct? Or is this a bad case of a circular dependence? If yes, how to accomplish "the same" in a different way? Thanks

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  • Problem using unicode in URLs with cgi.PATH_INFO in ColdFusion

    - by Loftx
    Hi there, My ColdFusion (MX7) site has search functionality which appends the search term to the URL e.g. http://www.example.com/search.cfm/searchterm. The problem I'm running into is this is a multilingual site, so the search term may be in another language e.g. ??????? leading to a search URL such as http://www.example.com/search.cfm/??????? The problem is when I come to retrieve the search term from the URL. I'm using cgi.PATH_INFO to retrieve the path of the search page and the search term and extracting the search term from this e.g. /search.cfm/searchterm however, when unicode characters are used in the search they are converted to question marks e.g. /search.cfm/??????. These appear actual question marks, rather than the browser not being able to format unicode characters, or them being mangled on output. I can't find any information about whether ColdFusion supports unicode in the URL, or how I can go about resolving this and getting hold of the complete URL in some way - does anyone have any ideas? Cheers, Tom

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  • Dealing with multiple generics in a method call

    - by thaBadDawg
    I've been dealing a lot lately with abstract classes that use generics. This is all good and fine because I get a lot of utility out of these classes but now it's making for some rather ugly code down the line. For example: abstract class ClassBase<T> { T Property { get; set; } } class MyClass : ClassBase<string> { OtherClass PropertyDetail { get; set; } } This implementation isn't all that crazy, except when I want to reference the abstract class from a helper class and then I have to make a list of generics just to make reference to the implemented class, like this below. class Helper { void HelpMe<C, T>(object Value) where C : ClassBase<T>, new() { DoWork(); } } This is just a tame example, because I have some method calls where the list of where clauses end up being 5 or 6 lines long to handle all of the generic data. What I'd really like to do is class Helper { void HelpMe<C>(object Value) where C : ClassBase, new() { DoWork(); } } but it obviously won't compile. I want to reference ClassBase without having to pass it a whole array of generic classes to get the function to work, but I don't want to reference the higher level classes because there are a dozen of those. Am I the victim of my own cleverness or is there an avenue that I haven't considered yet?

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  • How do I optimize this postfix expression tree for speed?

    - by Peter Stewart
    Thanks to the help I received in this post: I have a nice, concise recursive function to traverse a tree in postfix order: deque <char*> d; void Node::postfix() { if (left != __nullptr) { left->postfix(); } if (right != __nullptr) { right->postfix(); } d.push_front(cargo); return; }; This is an expression tree. The branch nodes are operators randomly selected from an array, and the leaf nodes are values or the variable 'x', also randomly selected from an array. char *values[10]={"1.0","2.0","3.0","4.0","5.0","6.0","7.0","8.0","9.0","x"}; char *ops[4]={"+","-","*","/"}; As this will be called billions of times during a run of the genetic algorithm of which it is a part, I'd like to optimize it for speed. I have a number of questions on this topic which I will ask in separate postings. The first is: how can I get access to each 'cargo' as it is found. That is: instead of pushing 'cargo' onto a deque, and then processing the deque to get the value, I'd like to start processing it right away. I don't yet know about parallel processing in c++, but this would ideally be done concurrently on two different processors. In python, I'd make the function a generator and access succeeding 'cargo's using .next(). But I'm using c++ to speed up the python implementation. I'm thinking that this kind of tree has been around for a long time, and somebody has probably optimized it already. Any Ideas? Thanks

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  • Solr/Lucene Scorer

    - by TFor
    We are currently working on a proof-of-concept for a client using Solr and have been able to configure all the features they want except the scoring. Problem is that they want scores that make results fall in buckets: Bucket 1: exact match on category (score = 4) Bucket 2: exact match on name (score = 3) Bucket 3: partial match on category (score = 2) Bucket 4: partial match on name (score = 1) First thing we did was develop a custom similarity class that would return the correct score depending on the field and an exact or partial match. The only problem now is that when a document matches on both the category and name the scores are added together. Example: searching for "restaurant" returns documents in the category restaurant that also have the word restaurant in their name and thus get a score of 5 (4+1) but they should only get 4. I assume for this to work we would need to develop a custom Scorer class but we have no clue on how to incorporate this in Solr. Another option is to create a custom SortField implementation similar to the RandomSortField already present in Solr. Maybe there is even a simpler solution that we don't know about. All suggestions welcome!

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  • create jquery array to use as options

    - by SoulieBaby
    Hi all, I'm sure this is really simple, but I can't seem to get it working. I have a "time" select list, which has a number as "rel" attached to each option. If the user changes the time select, I want a new list of options to display depending on what is selected. If that makes sense? Here's my first select: <select name="time" id="time"> <option value="7:00am" rel="10">7:00am</option> <option value="12:30pm" rel="16">12:30pm</option> </select> If the user selects 7:00am, I want a new option list (using jquery) to give options from 1 - 10. Like this: <select name="quantity" id="quantity"> <option value="1">1</option> <option value="2">2</option> <option value="3">3</option> ............................ <option value="10">10</option> </select> Here's what I have so far... <script type="text/javascript" language="javascript"> jQuery("#time").change(function(){ var positions = jQuery("#time :selected").attr("rel"); //this grabs the rel from time //this is where it should create a list of options to append(??) to the select list.. jQuery("#showQuantity").show(); //this shows the hidden field for quantity }); </script> I hope it makes sense, but I'm stuck on it. Thank you in advance :)

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  • Reversible numerical calculations in Prolog

    - by user8472
    While reading SICP I came across logic programming chapter 4.4. Then I started looking into the Prolog programming language and tried to understand some simple assignments in Prolog. I found that Prolog seems to have troubles with numerical calculations. Here is the computation of a factorial in standard Prolog: f(0, 1). f(A, B) :- A > 0, C is A-1, f(C, D), B is A*D. The issues I find is that I need to introduce two auxiliary variables (C and D), a new syntax (is) and that the problem is non-reversible (i.e., f(5,X) works as expected, but f(X,120) does not). Naively, I expect that at the very least C is A-1, f(C, D) above may be replaced by f(A-1,D), but even that does not work. My question is: Why do I need to do this extra "stuff" in numerical calculations but not in other queries? I do understand (and SICP is quite clear about it) that in general information on "what to do" is insufficient to answer the question of "how to do it". So the declarative knowledge in (at least some) math problems is insufficient to actually solve these problems. But that begs the next question: How does this extra "stuff" in Prolog help me to restrict the formulation to just those problems where "what to do" is sufficient to answer "how to do it"?

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  • OOP, Interface Design and Encapsulation

    - by Mau
    C# project, but it could be applied to any OO languages. 3 interfaces interacting: public interface IPublicData {} public /* internal */ interface IInternalDataProducer { string GetData(); } public interface IPublicWorker { IPublicData DoWork(); IInternalDataProducer GetInternalProducer(); } public class Engine { Engine(IPublicWorker worker) {} IPublicData Run() { DoSomethingWith(worker.GetInternalProducer().GetData()); return worker.DoWork(); } } Clearly Engine is parametric in the actual worker that does the job. A further source of parametrization is how we produce the 'internal data' via IInternalDataProducer. This implementation requires IInternalDataProducer to be public because it's part of the declaration of the public interface IPublicWorker. However, I'd like it to be internal since it's only used by the engine. A solution is make the IPublicWorker produce the internal data itself, but that's not very elegant since there's only a couple of ways of producing it (while there are many more worker implementations), therefore it's nice to delegate to a couple of separate concrete classes. Moreover, the IInternalDataProducer is used in more places inside the engine, so it's good for the engine to pass around the actual object. I'm looking for elegant ideas/patterns. Cheers :-)

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  • Problem with writing mobilesubstrate plugins for iOS

    - by overboming
    I am trying to hooking message sending for iOS 3.2, I implement my own hook on a working ExampleHook program I find on the web. But my hook apparently caused segmentation fault everytime it hooks and I don't know why. I want to hook to [NSURL initWithString:(NSString *)URLString relativeToURL:(NSURL *)baseURL; and here is my related implementation static id __$GFWInterceptor_NSURL_initWithString2(NSURL<GFWInterceptor> *_NSURL, NSString *URLString, NSURL* baseURL){ NSLog(@"We have intercepted this url: %@",URLString); [_NSURL __HelloNSURL_initWithString:URLString relativeToURL:baseURL]; establish hook Class _$NSURL = objc_getClass("NSURL"); MSHookMessage(_$NSURL, @selector(initWithString:relativeToURL:), (IMP) &__$GFWInterceptor_NSURL_initWithString2, "__HelloNSURL_"); original method declaration - (void)__HelloNSURL_initWithString:(NSString *)URLString relativeToURL:(NSURL *)baseURL; and here is my gdb backtrace Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: KERN_INVALID_ADDRESS at address: 0x74696e71 0x335625f8 in objc_msgSend () (gdb) bt 0 0x335625f8 in objc_msgSend () 1 0x32c05b1a in CFStringGetLength () 2 0x32c108a8 in _CFStringIsLegalURLString () 3 0x32b1c32a in -[NSURL initWithString:relativeToURL:] () 4 0x000877c0 in __$GFWInterceptor_NSURL_initWithString2 () 5 0x32b1c220 in +[NSURL URLWithString:relativeToURL:] () 6 0x32b1c1f4 in +[NSURL URLWithString:] () 7 0x3061c614 in createUniqueWebDataURL () 8 0x3061c212 in +[WebFrame(WebInternal) _createMainFrameWithSimpleHTMLDocumentWithPage:frameView:withStyle:editable:] () and apparently it hooks, but there is some memory issue there and I can't find anything to blame now

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  • Encapsulating user input of data for a class (C++)

    - by Dr. Monkey
    For an assignment I've made a simple C++ program that uses a superclass (Student) and two subclasses (CourseStudent and ResearchStudent) to store a list of students and print out their details, with different details shown for the two different types of students (using overriding of the display() method from Student). My question is about how the program collects input from the user of things like the student name, ID number, unit and fee information (for a course student) and research information (for research students): My implementation has the prompting for user input and the collecting of that input handled within the classes themselves. The reasoning behind this was that each class knows what kind of input it needs, so it makes sense to me to have it know how to ask for it (given an ostream through which to ask and an istream to collect the input from). My lecturer says that the prompting and input should all be handled in the main program, which seems to me somewhat messier, and would make it trickier to extend the program to handle different types of students. I am considering, as a compromise, to make a helper class that handles the prompting and collection of user input for each type of Student, which could then be called on by the main program. The advantage of this would be that the student classes don't have as much in them (so they're cleaner), but also they can be bundled with the helper classes if the input functionality is required. This also means more classes of Student could be added without having to make major changes to the main program, as long as helper classes are provided for these new classes. Also the helper class could be swapped for an alternative language version without having to make any changes to the class itself. What are the major advantages and disadvantages of the three different options for user input (fully encapsulated, helper class or in the main program)?

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  • NSOperations or NSThread for bursts of smaller tasks that continuously cancel each other?

    - by RickiG
    Hi I would like to see if I can make a "search as you type" implementation, against a web service, that is optimized enough for it to run on an iPhone. The idea is that the user starts typing a word; "Foo", after each new letter I wait XXX ms. to see if they type another letter, if they don't, I call the web service using the word as a parameter. The web service call and the subsequent parsing of the result I would like to move to a different thread. I have written a simple SearchWebService class, it has only one public method: - (void) searchFor:(NSString*) str; This method tests if a search is already in progress (the user has had a XXX ms. delay in their typing) and subsequently stops that search and starts a new one. When a result is ready a delegate method is called: - (NSArray*) resultsReady; I can't figure out how to get this functionality 'threaded'. If I keep spawning new threads each time a user has a XXX ms. delay in the typing I end up in a bad spot with many threads, especially because I don't need any other search, but the last one. Instead of spawning threads continuously, I have tried keeping one thread running in the background all the time by: - (void) keepRunning { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; SearchWebService *searchObj = [[SearchWebService alloc] init]; [[NSRunLoop currentRunLoop] run]; //keeps it alive [searchObj release]; [pool release]; } But I can't figure out how to access the "searchFor" method in the "searchObj" object, so the above code works and keeps running. I just can't message the searchObj or retrieve the resultReady objects? Hope someone could point me in the right direction, threading is giving me grief:) Thank you.

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  • How to specify allowed exceptions in WCF's configuration file?

    - by tucaz
    Hello! I´m building a set of WCF services for internal use through all our applications. For exception handling I created a default fault class so I can return treated message to the caller if its the case or a generic one when I have no clue what happened. Fault contract: [DataContract(Name = "DefaultFault", Namespace = "http://fnac.com.br/api/2010/03")] public class DefaultFault { public DefaultFault(DefaultFaultItem[] items) { if (items == null || items.Length== 0) { throw new ArgumentNullException("items"); } StringBuilder sbItems = new StringBuilder(); for (int i = 0; i Specifying that my method can throw this exception so the consuming client will be aware of it: [OperationContract(Name = "PlaceOrder")] [FaultContract(typeof(DefaultFault))] [WebInvoke(UriTemplate = "/orders", BodyStyle = WebMessageBodyStyle.Bare, ResponseFormat = WebMessageFormat.Json, RequestFormat = WebMessageFormat.Json, Method = "POST")] string PlaceOrder(Order newOrder); Most of time we will use just .NET to .NET communication with usual binds and everything works fine since we are talking the same language. However, as you can see in the service contract declaration I have a WebInvoke attribute (and a webHttp binding) in order to be able to also talk JSON since one of our apps will be built for iPhone and this guy will talk JSON. My problem is that whenever I throw a FaultException and have includeExceptionDetails="false" in the config file the calling client will get a generic HTTP error instead of my custom message. I understand that this is the correct behavior when includeExceptionDetails is turned off, but I think I saw some configuration a long time ago to allow some exceptions/faults to pass through the service boundaries. Is there such thing like this? If not, what do u suggest for my case? Thanks a LOT!

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  • Increasing time resolution of BOOST::progress timer

    - by feelfree
    BOOST::progress_timer is a very useful class to measure the running time of a function. However, the default implementation of progress_timer is not accurate enough and a possible way of increasing time resolution is to reconstruct a new class as the following codes show: #include <boost/progress.hpp> #include <boost/static_assert.hpp> template<int N=2> class new_progress_timer:public boost::timer { public: new_progress_timer(std::ostream &os=std::cout):m_os(os) { BOOST_STATIC_ASSERT(N>=0 &&N<=10); } ~new_progress_timer(void) { try { std::istream::fmtflags old_flags = m_os.setf(std::istream::fixed,std::istream::floatfield); std::streamsize old_prec = m_os.precision(N); m_os<<elapsed()<<"s\n" <<std::endl; m_os.flags(old_flags); m_os.precison(old_prec); } catch(...) { } } private: std::ostream &m_os; }; However, when I compile the codes with VC10, the following error appear: 'precison' : is not a member of 'std::basic_ostream<_Elem,_Traits>' Any ideas? Thanks.

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  • jQuery - Unchecking checkboxes that act like radio buttons

    - by Cecil
    Hey All, I have the following jQuery code to make my checkboxes act like radio buttons, so that only 1 of the 3 can be checked at a time. <script type="text/javascript" language="javascript"> $(document).ready(function() { $("#testing input:checkbox").change(function(){ var checkname = $(this).attr("name"); $("input:checkbox[name='" + checkname + "']").removeAttr("checked"); this.checked = true; }); }); </script> The checkboxes are layed out like the following: <input type="checkbox" id="testing" name="testing" value="B"> <input type="checkbox" id="testing" name="testing" value="I"> <input type="checkbox" id="testing" name="testing" value="A"> This works exactly how i want it to work, not a problem, except once i click one of the 3, i cant unclick it so that none of them are checked, this is what i want to happen, so along with being only able to click one at a time, im able to uncheck them completely. Any help would be grand :)

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  • Problem with Boost::Asio for C++

    - by Martin Lauridsen
    Hi there, For my bachelors thesis, I am implementing a distributed version of an algorithm for factoring large integers (finding the prime factorisation). This has applications in e.g. security of the RSA cryptosystem. My vision is, that clients (linux or windows) will download an application and compute some numbers (these are independant, thus suited for parallelization). The numbers (not found very often), will be sent to a master server, to collect these numbers. Once enough numbers have been collected by the master server, it will do the rest of the computation, which cannot be easily parallelized. Anyhow, to the technicalities. I was thinking to use Boost::Asio to do a socket client/server implementation, for the clients communication with the master server. Since I want to compile for both linux and windows, I thought windows would be as good a place to start as any. So I downloaded the Boost library and compiled it, as it said on the Boost Getting Started page: bootstrap .\bjam It all compiled just fine. Then I try to compile one of the tutorial examples, client.cpp, from Asio, found (here.. edit: cant post link because of restrictions). I am using the Visual C++ compiler from Microsoft Visual Studio 2008, like this: cl /EHsc /I D:\Downloads\boost_1_42_0 client.cpp But I get this error: /out:client.exe client.obj LINK : fatal error LNK1104: cannot open file 'libboost_system-vc90-mt-s-1_42.lib' Anyone have any idea what could be wrong, or how I could move forward? I have been trying pretty much all week, to get a simple client/server socket program for c++ working, but with no luck. Serious frustration kicking in. Thank you in advance.

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  • What database strategy to choose for a large web application

    - by Snoopy
    I have to rewrite a large database application, running on 32 servers. The hardware is up to date, each machine has two quad core Xeon and 32 GByte RAM. The database is multi-tenant, each customer has his own file, around 5 to 10 GByte each. I run around 50 databases on this hardware. The app is open to the web, so I have no control on the load. There are no really complex queries, so SQL is not required if there is a better solution. The databases get updated via FTP every day at midnight. The database is read-only. C# is my favourite language and I want to use ASP.NET MVC. I thought about the following options: Use two big SQL servers running SQL Server 2012 to serve the 32 servers with data. On the 32 servers running IIS hosting providing REST services. Denormalize the database and use Redis on each webserver. Use booksleeve as a Redis client. Use a combination of SQL Server and Redis Use SQL Server 2012 together with Hadoop Use Hadoop without SQL Server What is the best way for a read-only database, to get the best performance without loosing maintainability? Does Map-Reduce make sense at all in such a scenario? The reason for the rewrite is, the old app written in C++ with ISAM technology is too slow, the interfaces are old fashioned and not nice to use from an website, especially when using ajax. The app uses a relational datamodel with many tables, but it is possible to write one accerlerator table where all queries can be performed on, and all other information from the other tables are possible by a simple key lookup.

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  • Rtti data manipulation and consistency in Delphi 2010

    - by Coco
    Has anyone an idea, how I can make TValue using a reference to the original data? In my serialization project, I use (as suggested in XML-Serialization) a generic serializer which stores TValues in an internal tree-structure (similar to the MemberMap in the example). This member-tree should also be used to create a dynamic setup form and manipulate the data. My idea was to define a property for the Data: TDataModel <T> = class {...} private FData : TValue; function GetData : T; procedure SetData (Value : T); public property Data : T read GetData write SetData; end; The implementation of the GetData, SetData Methods: procedure TDataModel <T>.SetData (Value : T); begin FData := TValue.From <T> (Value); end; procedure TDataModel <T>.GetData : T; begin Result := FData.AsType <T>; end; Unfortunately, the TValue.From method always makes a copy of the original data. So whenever the application makes changes to the data, the DataModel is not updated and vice versa if I change my DataModel in a dynamic form, the original data is not affected. Sure I could always use the Data property before and after changing anything, but as I use lot of Rtti inside my DataModel, I do not realy want to do this anytime. Perhaps someone has a better suggestion?

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  • Finding part of a string that a user has sent via POST

    - by blerh
    My users can send links from popular file hosts like Rapidshare, Megaupload, Hotfile and FileFactory. I need to somehow find out what filehost they sent the link from and use the correct class for it appropriately. For example, if I sent a Rapidshare link in a form on my web page, I need to somehow cycle through each file host that I allow until I find the text rapidshare.com, then I know the user has posted a Rapidshare link. Perhaps a PHP example: switch($_POST['link']) { case strstr($_POST['link'], 'rapidshare.com'): // the link is a Rapidshare one break; case strstr($_POST['link'], 'megaupload.com'): // the link is a Megaupload one break; case strstr($_POST['link'], 'hotfile.com'): // the link is a Hotfile one break; case strstr($_POST['link'], 'filefactory.com'): // the link is a Filefactory one break; } However, I know for a fact this isn't correct and I'd rather not use a huge IF statement if I can help it. Does anyone have any solution to this problem? If you need me to explain more I can try, English isn't my native language so it's kinda hard. Thanks all.

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  • Help me write my LISP :) LISP environments, Ruby Hashes...

    - by MikeC8
    I'm implementing a rudimentary version of LISP in Ruby just in order to familiarize myself with some concepts. I'm basing my implementation off of Peter Norvig's Lispy (http://norvig.com/lispy.html). There's something I'm missing here though, and I'd appreciate some help... He subclasses Python's dict as follows: class Env(dict): "An environment: a dict of {'var':val} pairs, with an outer Env." def __init__(self, parms=(), args=(), outer=None): self.update(zip(parms,args)) self.outer = outer def find(self, var): "Find the innermost Env where var appears." return self if var in self else self.outer.find(var) He then goes on to explain why he does this rather than just using a dict. However, for some reason, his explanation keeps passing in through my eyes and out through the back of my head. Why not use a dict, and then inside the eval function, when a new "sub-environment" needs to be created, just take the existing dict and update the key/value pairs that need to be updated, and pass that new dict into the next eval? Won't the Python interpreter keep track of the previous "outer" envs? And won't the nature of the recursion ensure that the values are pulled out from "inner" to "outer"? I'm using Ruby, and I tried to implement things this way. Something's not working though, and it might be because of this, or perhaps not. Here's my eval function, env being a regular Hash: def eval(x, env = $global_env) ........ elsif x[0] == "lambda" then ->(*args) { eval(x[2], env.merge(Hash[*x[1].zip(args).flatten(1)])) } ........ end The line that matters of course is the "lambda" one. If there is a difference, what's importantly different between what I'm doing here and what Norvig did with his Env class? If there's no difference, then perhaps someone can enlighten me as to why Norvig uses the Env class. Thanks :)

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  • Warning: cast increases required alignment

    - by dash-tom-bang
    I'm recently working on this platform for which a legacy codebase issues a large number of "cast increases required alignment to N" warnings, where N is the size of the target of the cast. struct Message { int32_t id; int32_t type; int8_t data[16]; }; int32_t GetMessageInt(const Message& m) { return *reinterpret_cast<int32_t*>(&data[0]); } Hopefully it's obvious that a "real" implementation would be a bit more complex, but the basic point is that I've got data coming from somewhere, I know that it's aligned (because I need the id and type to be aligned), and yet I get the message that the cast is increasing the alignment, in the example case, to 4. Now I know that I can suppress the warning with an argument to the compiler, and I know that I can cast the bit inside the parentheses to void* first, but I don't really want to go through every bit of code that needs this sort of manipulation (there's a lot because we load a lot of data off of disk, and that data comes in as char buffers so that we can easily pointer-advance), but can anyone give me any other thoughts on this problem? I mean, to me it seems like such an important and common option that you wouldn't want to warn, and if there is actually the possibility of doing it wrong then suppressing the warning isn't going to help. Finally, can't the compiler know as I do how the object in question is actually aligned in the structure, so it should be able to not worry about the alignment on that particular object unless it got bumped a byte or two?

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  • Display Yearly Report When Data Not Available (CI, PHP, MySQL)

    - by tegaralaga
    First of all, i do apologize for my bad english, cos english isn't my native language. I want to display yearly report based on month, let say i got order on January, August, December, but the rest there's no order. So in MySQL database only have 3 order (Jan,Aug,Dec). When i query use CI ( select month(order_date) as month_name , count(order_id) as amount from order where year(order_date)=2011 group by month(order_date) ) there's only 3 data let say the 3 data is (use $query-result_array()) Array ( [0] => Array ( [month_num] => 1 [amount] => 4 ) [1] => Array ( [month_num] => 8 [amount] => 1 ) [2] => Array ( [month_num] => 12 [amount] => 19 ) ) how to make it to 12 data (12 Month) the array become like this (when data not available the amount is 0) Array ( [0] => Array ( [month_num] => 1 [amount] => 4 ) [1] => Array ( [month_num] => 2 [amount] => 0 ) [2] => Array ( [month_num] => 3 [amount] => 0 ) etc ) Thanks in advance :)

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  • How to enforce users to create objects of class derived from mine with "new" only?

    - by sharptooth
    To implement reference counting we use an IUnknown-like interface and a smart pointer template class. The interface has implementation for all the reference-count methods, including Release(): void IUnknownLike::Release() { if( --refCount == 0 ) { delete this; } } The smart pointer template class has a copy constructor and an assignment operator both accepting raw pointers. So users can do the following: class Class : public IUnknownLike { }; void someFunction( CSmartPointer<Class> object ); //whatever function Class object; someFunction( &object ); and the program runs into undefined behavior - the object is created with reference count zero, the smart pointer is constructed and bumps it to one, then the function returns, smart pointer is destroyed, calls Release() which leads to delete of a stack-allocated variable. Users can as well do the following: struct COuter { //whatever else; Class inner;// IUnknownLike descendant }; COuter object; somefunction( &object.Inner ); and again an object not created with new is deleted. Undefined behavior at its best. Is there any way to change the IUnknownLike interface so that the user is forced to use new for creating all objects derived from IUnknownLike - both directly derived and indirectly derived (with classes in between the most derived and the base)?

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  • Endianness and C API's: Specifically OpenSSL.

    - by Hassan Syed
    I have an algorithm that uses the following OpenSSL calls: HMAC_update() / HMAC_final() // ripe160 EVP_CipherUpdate() / EVP_CipherFinal() // cbc_blowfish These algorithm take a unsigned char * into the "plain text". My input data is comes from a C++ std::string::c_str() which originate from a protocol buffer object as a encoded UTF-8 string. UTF-8 strings are meant to be endian neutrial. However I'm a bit paranoid about how OpenSSL may perform operations on the data. My understanding is that encryption algorithms work on 8-bit blocks of data, and if a unsigned char * is used for pointer arithmetic when the operations are performed the algorithms should be endian neutral and I do not need to worry about anything. My uncertainty is compounded by the fact that I am working on a little-endian machine and have never done any real cross-architecture programming. My beliefs/reasoning are/is based on the following two properties std::string (not wstring) internally uses a 8-bit ptr and a the resulting c_str() ptr will itterate the same way regardless of the CPU architecture. Encryption algorithms are either by design, or by implementation, endian neutral. I know the best way to get a definitive answer is to use QEMU and do some cross-platform unit tests (which I plan to do). My question is a request for comments on my reasoning, and perhaps will assist other programmers when faced with similar problems.

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  • String literal recognition problem

    - by helicera
    Hello! I'm trying to recognize string literal by reading string per symbol. Here is a sample code: #region [String Literal (")] case '"': // {string literal ""} { // skipping '"' ChCurrent = Line.ElementAtOrDefault<Char>(++ChPosition); while(ChCurrent != '"') { Value.Append(ChCurrent); ChCurrent = Line.ElementAtOrDefault<Char>(++ChPosition); if(ChCurrent == '"') { // "" sequence only acceptable if(Line.ElementAtOrDefault<Char>(ChPosition + 1) == '"') { Value.Append(ChCurrent); // skip 2nd double quote ChPosition++; // move position next ChCurrent = Line.ElementAtOrDefault<Char>(++ChPosition); } } else if(default(Char) == ChCurrent) { // message: unterminated string throw new ScanningException(); } } ChPosition++; break; } #endregion When I run test: [Test] [ExpectedException(typeof(ScanningException))] public void ScanDoubleQuotedStrings() { this.Scanner.Run(@"""Hello Language Design""", default(System.Int32)); this.Scanner.Run(@"""Is there any problems with the """"strings""""?""", default(System.Int32)); this.Scanner.Run(@"""v#:';?325;.<>,|+_)""(*&^%$#@![]{}\|-_=""", default(System.Int32)); while(0 != this.Scanner.TokensCount - 1) { Assert.AreEqual(Token.TokenClass.StringLiteral, this.Scanner.NextToken.Class); } } It passes with success.. while I'm expecting to have an exception according to unmatched " mark in this.Scanner.Run(@"""v#:';?325;.<>,|+_)""(*&^%$#@![]{}\|-_=""", default(System.Int32)); Can anyone explain where is my mistake or give an advice on algorithm.

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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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