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  • Assign to a slice of a Python list from a lambda

    - by Bushman
    I know that there are certain "special" methods of various objects that represent operations that would normally be performed with operators (i.e. int.__add__ for +, object.__eq__ for ==, etc.), and that one of them is list.__setitem, which can assign a value to a list element. However, I need a function that can assign a list into a slice of another list. Basically, I'm looking for the expression equivalent of some_list[2:4] = [2, 3].

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  • correct way to store an exception in a variable

    - by Evan Teran
    I have an API which internally has some exceptions for error reporting. The basic structure is that it has a root exception object which inherits from std::exception, then it will throw some subclass of that. Since catching an exception thrown in one library and catching it in another can lead to undefined behavior (at least Qt complains about it and disallows it in many contexts). I would like to wrap the library calls in functions which will return a status code, and if an exception occurred, a copy of the exception object. What is the best way to store an exception (with it's polymorphic behavior) for later use? I believe that the c++0x futures API makes use of something like this. So what is the best approach? The best I can think of is to have a clone() method in each exception class which will return a pointer to an exception of the same type. But that's not very generic and doesn't deal with standard exceptions at all. Any thoughts?

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  • Should I use implicit conversions to enforce preconditions?

    - by Malvolio
    It occurs to me that I could use use implicit conversions to both announce and enforce preconditions. Consider this: object NonNegativeDouble { implicit def int2nnd(d : Double) : NonNegativeDouble = new NonNegativeDouble(d) implicit def nnd2int(d : NonNegativeDouble) : Double = d.v def sqrt(n : NonNegativeDouble) : NonNegativeDouble = scala.math.sqrt(n) } class NonNegativeDouble(val v : Double ) { if (v < 0) { throw new IllegalArgumentException("negative value") } } object Test { def t1 = { val d : Double = NonNegativeDouble.sqrt(3.0); printf("%f\n", d); val n : Double = NonNegativeDouble.sqrt(-3.0); } } Ignore for the moment the actual vacuity of the example: my point is, the subclass NonNegativeDouble expresses the notion that a function only takes a subset of the entire range of the class's values. First is this: A good idea, a bad idea, or an obvious idea everybody else already knows about Second, this would be most useful with basic types, like Int and String. Those classes are final, of course, so is there a good way to not only use the restricted type in functions (that's what the second implicit is for) but also delegate to all methods on the underlying value (short of hand-implementing every delegation)?

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  • python set difference

    - by user1311992
    I'm doing a set difference operation in Python: from sets import Set from mongokit import ObjectId x = [ObjectId("4f7aba8a43f1e51544000006"), ObjectId("4f7abaa043f1e51544000007"), ObjectId("4f7ac02543f1e51a44000001")] y = [ObjectId("4f7acde943f1e51fb6000003")] print list(Set(x).difference(Set(y))) I'm getting: [ObjectId('4f7abaa043f1e51544000007'), ObjectId('4f7ac02543f1e51a44000001'), ObjectId('4f7aba8a43f1e51544000006')] I need to get the first element for next operation which is important. How can I retain the list x in original format?

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  • Only one instance of a scriptmanager can exist on a page

    - by dotnetdev
    Hi, I design an ASP.NET web usercontrol and with a maskeditor and scriptmanager, I always get an object reference not set to an instance of an object exception at runtime. Stacktrace is: [InvalidOperationException: Only one instance of a ScriptManager can be added to the page.] System.Web.UI.ScriptManager.OnInit(EventArgs e) +384613 System.Web.UI.Control.InitRecursive(Control namingContainer) +333 System.Web.UI.Control.InitRecursive(Control namingContainer) +210 System.Web.UI.Control.InitRecursive(Control namingContainer) +210 System.Web.UI.Control.InitRecursive(Control namingContainer) +210 System.Web.UI.Control.InitRecursive(Control namingContainer) +210 System.Web.UI.Control.InitRecursive(Control namingContainer) +210 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +378 What causes this? Thanks

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  • How do I retrieve readonly values when using a DetailsView control to update a record?

    - by lincolnk
    I'm using a detailsview control to update a record, however in this particular case there's only one field that can be changed out of a many. The update method for my object takes all fields as parameters. When the detailsview's updating method fires, the values for the readonly fields (those rendered as a Label) are not available in the e.NewValues collection. I'm currently grabbing a reference to the object when the detailsview is databound (in the objectdatasource selected event handler), storing it in session and manually adding entries to the e.NewValues collection when updating fires. It works but seems kind of heavy handed. So, is there a better way to get the read only values back into my update method? Or is there a better way of doing this altogether?

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  • Is this pointer initialization necessary?

    - by bstullkid
    Lets say I have the following: CHARLINK * _init_link(CHARLINK **link) { short i; (*link)->cl = (CHARLINK **) calloc(NUM_CHARS, sizeof(CHARLINK *)); for (i = 0; i < NUM_CHARS; i++) (*link)->cl[i] = NULL; return (*link); } Is the loop to initialize each element to NULL necessary or are they automatically NULL from calloc?

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  • Is there a way to automate MS Office applications without license?

    - by james-h-l
    I am currently writing an application that will perform automation in Excel. I have MS Office (2007) installed on my work computer and the application is working fine referencing the the Microsoft Excel 12.0 Object Lirary. The target machine has the Office installed but not registered. It is one of those preinstalled editions. Attempting to run the application on the target machine I get an error saying Office is not installed? I'm assuming then you have to have a registed Office to use the object libraries? Is there anyway around this as I do not have a Office license key lying around and its quite expensive?

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  • GameKit Bluetooth Transfer Problem

    - by David Schiefer
    Hi, I am trying to send a file via Bluetooth using the GameKit framework. The problem I am having though is that I can only send one NSData object at a time, but I need to save it on the other end. this obviously isn't possible without knowing the filename, but i don't know how to transmit that. I've tried to convert it to a string NSData*data = [NSData dataWithContentsOfFile:urlAddress]; but i can only send one NSData object, not two. Has anyone come across this problem yet?

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  • Find the right parameters for an event without using Design Mode in Visual Studio 2010

    - by Jason
    Is there a way to know what parameters are needed by an event in Visual Studio 2010? Let's say I have a DropDownList control and I want to bind a method to the "OnSelectedIndexChanged", I would do something like this In the ASPX File: <asp:DropDownList ID="lstMyList" runat="server" OnSelectedIndexChanged="lstMyList_SelectedIndexChanged"></asp:DropDownList> In the codebehind: protected void lstMyList_SelectedIndexChanged(object sender, EventArgs e) { ... } Is there a way to know what parameters the method needs? (In this case, an object for the sender and an EventArgs parameter for the event.) I know you can easily create the method by double-clicking the right event in Design Mode, but it does a mess with your code so I prefer not to use it. Thanks!

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  • GWT: What is the way to handle Click on GWT FlowPanel

    - by shaman.sir
    May be a dumb question, but GWT FlowPanel (raw div element) does not provides something to handle a mouseclick/mousemovement on it. Overriding onBrowserEvent do not works either. If setting onclick event using native JavaScript (need to specify positive height before, 'div' have a height of 0 if not specified), then catching these events is working properly. Is there a way to do it without using JSNI?

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  • Simulating click with javascript on document

    - by Charlie
    Is it possible to simulate a click on a webpage using javascript but without defining a specific element, but rather just specifying the document? I would have liked to do something like this, and if the location happens to have a link, then this will be pressed: function simulateClick(x, y) { var evt = window.createEvent("MouseEvents"); evt.initMouseEvent("click", true, true, window, x, y, x, y, 1, false, false, false, false, 0, null); window.dispatchEvent(evt); }

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  • C# - Dictionary with generic array as value

    - by alhazen
    In my class, I want to use a dictionary with the following declaration: Dictionary<string, T[]> Since the operations of my class are exactly the same for all generic types, I do not wish to define my class as generic (which means I would have to create a separate instance of my class for each generic type I insert into the dictionary ?). One alternative I'm attempting is to use Dictionary<string, object> instead: public void Add<T>(string str, T value) { // Assuming key already exists var array = (T[]) dictionary[str]; array[0] = value; } However, when iterating over the dictionary, how do I cast the object value back to an array ? foreach(string strKey in dictionary.Keys) { var array = (T[]) dictionary[strKey]; // How to cast here ? //... array[0] = default(T); } Thanks.

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  • Django or Drupal, which one should I use that suits best my needs ?

    - by HJ-INCPP
    Hello, I want to learn and use Drupal or Django for the following: dynamic web sites, medium database, multi-level users, paypal integration, content managment, speed (developing), security I like MVC, ORM and object-oriented prg. Which is better to jump into ? Which one is more mature, powerful, understandable, object-oriented and easier to use by the time ? What about Python Spring ... Also, which of these 3 are better documented, are better for a cv and have more extensions? Known languages: php, java, mysql Thank you !

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  • C++ interface inheritance problem

    - by james t
    Hey, i'm trying to create a c++ stomp client, my client constructor is : Client(std::string &server, short port, std::string &login, std::string &pass, Listener &listener); it gets a listener object which when Listener is the following interface : class Listener { virtual void message(StmpMessage message) =0; }; now i attempt to instantiate a client in a test class : class test : public virtual Listener { public: void message(StmpMessage message) { message.prettyPrint(); } int main(int argc, char* argv[]) { Client client("127.0.0.1", 61613, *this); return 0; } }; i'm sending this to the client because this is a listener object, i get the following error : /Users/mzruya/Documents/STOMPCPP/main.cpp:18: error: no matching function for call to 'Client::Client(const char [10], int, test&)' /Users/mzruya/Documents/STOMPCPP/Client.h:43: note: candidates are: Client::Client(std::string&, short int, std::string&, std::string&, Listener&) /Users/mzruya/Documents/STOMPCPP/Client.h:37: note: Client::Client(const Client&)

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  • help designing a method, should I use out or ref or return the type?

    - by Blankman
    I have a method that I will use in the following contexts: 1. User user = null; if(...) { user = defaultUser; SetUser(a,b,user); } else { SetUser(a,b,user); } SaveUser(user); So some cases are where user may be null, while in other cases it will already be initialized. How should I design the SetUser method? I currently have it like so, but this causes an error when user is null. public void SetUser(object a, object b, User user) { if(user == null) user = new User(); user.Security = a.security; user.Blah = b.type; }

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  • Using Property Builtin with GAE Datastore's Model

    - by ejel
    I want to make attributes of GAE Model properties. The reason is for cases like to turn the value into uppercase before storing it. For a plain Python class, I would do something like: Foo(db.Model): def get_attr(self): return self.something def set_attr(self, value): self.something = value.upper() if value != None else None attr = property(get_attr, set_attr) However, GAE Datastore have their own concept of Property class, I looked into the documentation and it seems that I could override get_value_for_datastore(model_instance) to achieve my goal. Nevertheless, I don't know what model_instance is and how to extract the corresponding field from it. Is overriding GAE Property classes the right way to provides getter/setter-like functionality? If so, how to do it? Added: One potential issue of overriding get_value_for_datastore that I think of is it might not get called before the object was put into datastore. Hence getting the attribute before storing the object would yield an incorrect value.

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  • Problem at JUnit test with generics

    - by Tom Brito
    In my utility method: public static <T> T getField(Object obj, Class c, String fieldName) { try { Field field = c.getDeclaredField(fieldName); field.setAccessible(true); return (T) field.get(obj); } catch (Exception e) { e.printStackTrace(); fail(); return null; } } The line return (T) field.get(obj); gives the warning "Type safety: Unchecked cast from Object to T"; but I cannot perform instanceof check against type parameter T, so what am I suppose to do here?

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