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  • string s; &s+1; Legal? UB?

    - by John Dibling
    Consider the following code: #include <cstdlib> #include <iostream> #include <string> #include <vector> #include <algorithm> using namespace std; int main() { string myAry[] = { "Mary", "had", "a", "Little", "Lamb" }; const size_t numStrs = sizeof(myStr)/sizeof(myAry[0]); vector<string> myVec(&myAry[0], &myAry[numStrs]); copy( myVec.begin(), myVec.end(), ostream_iterator<string>(cout, " ")); return 0; } Of interest here is &myAry[numStrs]: numStrs is equal to 5, so &myAry[numStrs] points to something that doesn't exist; the sixth element in the array. There is another example of this in the above code: myVec.end(), which points to one-past-the-end of the vector myVec. It's perfecly legal to take the address of this element that doesn't exist. We know the size of string, so we know where the address of the 6th element of a C-style array of strings must point to. So long as we only evaluate this pointer and never dereference it, we're fine. We can even compare it to other pointers for equality. The STL does this all the time in algorithms that act on a range of iterators. The end() iterator points past the end, and the loops keep looping while a counter != end(). So now consider this: #include <cstdlib> #include <iostream> #include <string> #include <vector> #include <algorithm> using namespace std; int main() { string myStr = "Mary"; string* myPtr = &myStr; vector<string> myVec2(myPtr, &myPtr[1]); copy( myVec2.begin(), myVec2.end(), ostream_iterator<string>(cout, " ")); return 0; } Is this code legal and well-defined? It is legal and well-defined to take the address of an array element past the end, as in &myAry[numStrs], so should it be legal and well-defined to pretend that myPtr is also an array?

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  • Is it any loose coupling mechanism in Objective-C + Cocoa like C# delegates or C++Qt signals+slots?

    - by Eye of Hell
    Hello. For a large programs, the standard way to chalenge a complexity is to divide a program code into small objects. Most of the actual programming languages offer this functionality via classes, so is Objective-C. But after source code is separated into small object, the second challenge is to somehow connect them with each over. Standard approaches, supported by most languages are compositon (one object is a member field of another), inheritance, templates (generics) and callbacks. More cryptic techniques include method-level delagates (C#) and signals+slots (C++Qt). I like the delegates / signals idea, since while connecting two objects i can connect individual methods with each over, without objects knowing anything of each over. For C#, it will look like this: var object1 = new CObject1(); var object2 = new CObject2(); object1.SomethingHappened += object2.HandleSomething; In this code, is object1 calls it's SomethingHappened delegate (like a normal method call) the HandleSomething method of object2 will be called. For C++Qt, it will look like this: var object1 = new CObject1(); var object2 = new CObject2(); connect( object1, SIGNAL(SomethingHappened()), object2, SLOT(HandleSomething()) ); The result will be exactly the same. This technique has some advantages and disadvantages, but generally i like it more than interfaces since if program code base grows i can change connections and add new ones without creating tons of interfaces. After examination of Objective-C i havn't found any way to use this technique i like :(. It seems that Objective-C supports message passing perfectly well, but it requres for object1 to have a pointer to object2 in order to pass it a message. If some object needs to be connected to lots of other objects, in Objective-C i will be forced to give him pointers to each of the objects it must be connected. So, the question :). Is it any approach in Objective-C programming that will closely resemble delegate / signal+slot types of connection, not a 'give first object an entire pointer to second object so it can pass a message to it'. Method-level connections are a bit more preferable to me than object-level connection ^_^.

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  • Android XML-RPC Serialization Issue

    - by Josh Pennington
    I am attempting to use Android XML-RPC and for some calls I get the following exception: W/System.err( 837): java.io.IOException: Cannot serialize java.lang.Object@43759748 It looks like it is having troubles serializing the returned data, but I cannot find much documentation on how to actually use Android XML-RPC. The way I am using Android XML-RPC is as follows: Object response = (Object)client.call("sales_order.list", new Object()); This one is pretty odd. I have tried setting this call up in a few different ways (using HashMaps, not passing second variable, etc) and the response I get is that sales_order.list is not a valid Method. I have been able to login to the service using the following code: this.sessionId = (String)client.call("login", this.apiUserName, this.apiPassword); Does anyone have any ideas or a good resource on how to use Android XML-RPC? Thanks

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  • How to detect a sign change for elements in a numpy array

    - by cb160
    I have a numpy array with positive and negative values in. a = array([1,1,-1,-2,-3,4,5]) I want to create another array which contains a value at each index where a sign change occurs (For example, if the current element is positive and the previous element is negative and vice versa). For the array above, I would expect to get the following result array([0,0,1,0,0,1,0]) Alternatively, a list of the positions in the array where the sign changes occur or list of booleans instead of 0's and 1's is fine.

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  • [Android] Putting Serializable Classes into SQL?

    - by CaseyB
    Here's the situation. I have a bunch of objects that implement Serializable that I want to store in a SQL database. I have two questions Is there a way to serialize the object directly into the database Is that the best way to do it or should I Write the object out to a formatting String and put it in the database that way and then parse it back out Write each member to the database with a field that is unique to each object

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  • WPF: Trying to add a class to Window.Resources Again

    - by user3952846
    I did exactly the same thing, but still the same error is occurring: "The tag 'CenterToolTipConverter' does not exist in XML namespace 'clr-namespace:WpfApplication1;assembly=WpfApplication1'. Line 12 Position 10." CenterToolTipConverter.cs namespace WpfApplication1 { public class CenterToolTipConverter : IMultiValueConverter { public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture) { if (values.FirstOrDefault(v => v == DependencyProperty.UnsetValue) != null) { return double.NaN; } double placementTargetWidth = (double)values[0]; double toolTipWidth = (double)values[1]; return (placementTargetWidth / 2.0) - (toolTipWidth / 2.0); } public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture) { throw new NotSupportedException(); } } } MainWindow.xaml <Window x:Class="WpfApplication1.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:WpfApplication1;assembly=WpfApplication1" Title="MainWindow" Height="350" Width="525"> <Window.Resources> <local:CenterToolTipConverter x:Key="myCenterToolTipConverter"/> </Window.Resources> </Window> What am I doing wrong? Thanks in advance!!!

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  • Type contraint problem of C#

    - by user351565
    I meet a problem about type contraint of c# now. I wrote a pair of methods that can convert object to string and convert string to object. ex. static string ConvertToString(Type type, object val) { if (type == typeof(string)) return (string)val; if (type == typeof(int)) return val.ToString(); if (type.InSubclassOf(typeof(CodeObject))) return ((CodeObject)val).Code; } static T ConvertToObject<T>(string str) { Type type = typeof(T); if (type == typeof(string)) return (T)(object)val; if (type == typeof(int)) return (T)(object)int.Parse(val); if (type.InSubclassOf(typeof(CodeObject))) return Codes.Get<T>(val); } where CodeObject is a base class of Employees, Offices ..., which can fetch by static method Godes.Get where T: CodeObject but the code above cannot be compiled because error #CS0314 the generic type T of method ConvertToObject have no any constraint but Codes.Get request T must be subclass of CodeObject i tried use overloading to solve the problem but not ok. is there any way to clear up the problem? like reflection?

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  • getting node value exception

    - by Aswan
    Hi Folks <amount currency="USD">1000500</amount> while parsing above string i am getting only attribute value .when i try to get node value null pointer exception for getting node value using NodeList amountList= estimateElement.getElementsByTagName("amount"); Element amtElement= (Element)amountList.item(0); String amount=amtElement.getFirstChild().getnodevalue() Thanks in advance Aswan

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  • Best approach to synchronising properties across threads

    - by user290796
    Hi, I'm looking for some advice on the best approach to synchronising access to properties of an object in C++. The application has an internal cache of objects which have 10 properties. These objects are to be requested in sets which can then have their properties modified and be re-saved. They can be accessed by 2-4 threads at any given time but access is not intense so my options are: Lock the property accessors for each object using a critical section. This means lots of critical sections - one for each object. Return copies of the objects when requested and have an update function which locks a single critical section to update the object properties when appropriate. I think option 2 seems the most efficient but I just want to see if I'm missing a hidden 3rd option which would be more appropriate. Thanks, J

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  • Translate from c# to c++

    - by Xaver
    Help to translate from c# code to c++ code. Type tp = Type.GetTypeFromProgID("Shell.Application"); object o = Activator.CreateInstance(tp); Object[] arg = new Object[1]; arg[0] = "C:\\!!"; object b = o.GetType().InvokeMember(@"NameSpace", BindingFlags.Public | BindingFlags.InvokeMethod, null, o, arg); arg[0] = "ftp://anonymous:[email protected]/bussys/1394"; b.GetType().InvokeMember(@"CopyHere", BindingFlags.Public | BindingFlags.InvokeMethod, null, b, arg);

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  • How to reference a particular JSON in a function call.

    - by Jane Wilkie
    Hi guys! I have two javascript routines.. the first one declares some JSON and it contains a function that takes two arguments, the first argument being the json object that needs traversing and the second argument is the tab that the rendering is done in. The second routine merely passes the name of the JSON that needs traversing and tab to render in. The code is below.... <script language="JavaScript1.2" type="text/javascript"> var arr = [ {"id":"10", "class":"child-of-9", "useless":"donotneed"}, {"id":"11", "class":"child-of-10", "useless":"donotneed"}]; var arrtwo = [ {"id":"12", "class":"child-of-12", "useless":"donotneed"}, {"id":"13", "class":"child-of-13", "useless":"donotneed"}]; function render_help(json,tab){ var html=''; for(var i=0;i<json.length;i++){ var obj = json[i]; for(var key in obj){ var attrName = key; var attrValue = obj[key]; if (attrName == "id"){ html = html +'<B>'+attrValue+'</B>'+'<BR><BR>'; }else if (attrName == "class"){ html = html + attrValue + '<BR><BR>'; } } } document.getElementById(tab).innerHTML=(html); } </script> <script language="JavaScript1.2" type="text/javascript"> render_help(arr,"helptab"); </script> Various testing and strategically placed alert boxes indicate that the tab parameter is being passed and interpreted correctly. I know this because when I change .... document.getElementById(tab).innerHTML=(html); to document.getElementById(tab).innerHTML=("Howdy"); and it renders "Howdy" just fine. Putting an alert box (alert(json)) in to check the value of json yields.... [object.Object],[object.Object] The JSON object remains elusive. For the purposes of this scripting I need the JSON "arr" to be iterated over. I feel like the answer is fairly obvious so far no luck. Admittedly I am new with Javascript and I am apparently missing something. Does anyone have a clue as to what I'm overlooking here? Happy New Year to you all! Janie

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  • help me with typecasting problem ...

    - by Anil Namde
    I would like to create a function which can take two arguments object and type and then type cast the object to appropriate type using the type parameter. Is that possible ? how can i achieve it ? public class TEST { public int test; } object ot = new TEST(); Type type = typeof(TEST); TEST t = (type)ot; //Function will be something like this public string SearializeObject(Object obj, Type t) { //check if obj is of type t if(obj is of type t){ //cast obj to type t to read it ((Type t)obj).someMethod } }

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  • How do linq Last() work?

    - by acidzombie24
    I dont understand how current can be null and last can be an object while last being a LINQ function. I thought last uses GetEnumerator and keeps going until current == null and returns the object. However as you can see the first GetEnumerator().Current is null and last somehow returns an object. How do linq Last() work? var.GetEnumerator().Current var.Last()

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  • insert DropDownList and TextField in Gridview

    - by userk
    HI,I need to create a GridView which DataSource is an object. Depending on the object I may need some columns with DropDownLists or TextFields (but not all rows) As I don't know the number or columns, they have to be dynamic. I found this solution: TemplateField t = new TemplateField(); t.HeaderTemplate = new GridViewTemplate("header", "title"); t.ItemTemplate = new GridViewTemplate("combobox", "val"); GridView1.Columns.Add(t); GridView1.DataSource = ds; GridView1.DataBind(); Where GridViewTemplate extends ITemplate. This didn't work for me, it fills all rows of a column and I had no way to control witch DropDownList and TextFields need to be created (object info). All the DropDownLists need to have an ID also only known by the object. There are some way I can do this?

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  • Windows App. Thread Aborting Issue

    - by Patrick
    I'm working on an application that has to make specific decisions based on files that are placed into a folder being watched by a file watcher. Part of this decision making process involves renaming files before moving them off to another folder to be processed. Since I'm working with files of all different sizes I created an object that checks the file in a seperate thread to verify that it is "available" and when it is it fires an event. When I run the rename code from inside this available event it works. public void RenameFile_Test() { string psFilePath = @"C:\File1.xlsx"; tgt_File target = new FileObject(psFilePath); target.FileAvailable += new FileEventHandler(OnFileAvailable); target.FileUnAvailable += new FileEventHandler(OnFileUnavailable); } private void OnFileAvailable(object source, FileEventArgs e) { ((FileObject)source).RenameFile(@"C:\File2.xlsx"); } The problem I'm running into is that when the extensions are different from the source file and the rename to file I am making a call to a conversion factory that returns a factory object based on the type of conversion and then converts the file accordingly before doing the rename. When I run that particular piece of code in unit test it works, the factory object is returned, and the conversion happens correctly. But when I run it within the process I get up to the... moExcelApp = new Application(); part of converting an .xls or .xlsx to a .csv and i get a "Thread was being Aborted" error. Any thoughts? Update: There is a bit more information and a bit of map of how the application works currently. Client Application running FSW On File Created event Creates a FileObject passing in the path of the file. On construction the file is validated: if file exists is true then, Thread toAvailableCheck = new Thread(new ThreadStart(AvailableCheck)); toAvailableCheck.Start(); The AvailableCheck Method repeatedly tries to open a streamreader to the file until the reader is either created or the number of attempts times out. If the reader is opened, it fires the FileAvailable event, if not it fires the FileUnAvailable event, passing back itself in the event. The client application is wired to catch those events from inside the Oncreated event of the FSW. the OnFileAvailable method then calls the rename functionality which contains the excel interop call. If the file is being renamed (not converted, extensions stay the same) it does a move to change the name from the old file name to the new, and if its a conversion it runs a conversion factory object which returns the correct type of conversion based on the extensions of the source file and the destination file name. If it is a simple rename it works w/o a problem. If its a conversion (which is the XLS to CSV object that is returned as a part of the factory) the very first thing it does is create a new application object. That is where the application bombs. When i test the factory and conversion/rename process outside of the thread and in its own unit test the process works w/o a problem. Update: I tested the Excel Interop inside a thread by doing this: [TestMethod()] public void ExcelInteropTest() { Thread toExcelInteropThreadTest = new Thread(new ThreadStart(Instantiate_App)); toExcelInteropThreadTest.Start(); } private void Instantiate_App() { Application moExcelApp = new Application(); moExcelApp.Quit(); } And on the line where the application is instatntiated I got the 'A first chance exception of type 'System.Threading.ThreadAbortException' error. So I added; toExcelInteropThreadTest.SetApartmentState(ApartmentState.MTA); after the thread instantiation and before the thread start call and still got the same error. I'm getting the notion that I'm going to have to reconsider the design.

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  • How to discover getters and setters on hibernate objects

    - by Michael Jones
    I need to find a way of taking a hibernate object and discovering at runtime all of the getter methods that relate to persistable fields. I'm using annotations in the classes but have previously had difficulties working with them (I ran into a 2 year old bug the java developers still haven't fixed). Does anyone know how I can do this please, ideally without using annotations? Thanks. PS - What I'm trying to do here is to update a new object with values from an existing object dynamically.

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  • Using CompareTo() on different .NET types (e.g. int vs. double)

    - by Yossin
    Hi, I've got a static method that accepts two object type variables and runs the CompareTo() method: public static int Compare(Object objA, Object objB) { return (((IComparable)objA).CompareTo(objB)); } Problem is that CompareTo() throws an exception when trying to compare between different types (e.g. int and double). Does any one know of a better way in C#, to compare between two different types? Or a workaround to this problem? Thanks

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  • Cannot bind to list<T>.property or list<T>.item.property in details section of Telerik report

    - by fluf
    I have created a Telerik report and I am setting the datasource on runtime to an object with some properties and a List. I am using the properties in the page and report header sections and i want to use the list as the details. Now the problem is binding to the List's item properties in the details section. I have played around with the expression builder and it seems that i should access the properties like this : [=Fields.myList.Item.myProperty] when i run the program i get a nice big red rectangle with the following error : An error has occured while processing TextBox 'textBox28':Common Language Runtime detected an invalid program. I have tried to change different variants of expression which also gives me other errors [=Fields.myList.myPropery] An error has occured while processing TextBox 'textBox28': The expression contains object 'myProperty' that is not defined in the current context. The closest i have gotton was with the object it self, which outputs the object.toString() [=Fields.myList]

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  • Rails: update_attribute vs update_attributes

    - by Sam
    Object.update_attribute(:only_one_field, "Some Value") Object.update_attributes(:field1 => "value", :field2 => "value2", :field3 => "value3") Both of these will update an object without having to explicitly tell AR to update. Rails API says: for update_attribute Updates a single attribute and saves the record without going through the normal validation procedure. This is especially useful for boolean flags on existing records. The regular update_attribute method in Base is replaced with this when the validations module is mixed in, which it is by default. for update_attributes Updates all the attributes from the passed-in Hash and saves the record. If the object is invalid, the saving will fail and false will be returned. So if I don't want to have the object validated I should use update_attribute. What if I have this update on a before_save, will it stackoverflow? My question is does update_attribute also bypass the before save or just the validation. Also, what is the correct syntax to pass a hash to update_attributes... check out my example at the top.

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  • STL map - insert or update

    - by CodeJunkie
    I have a map of objects and I want to update the object mapped to a key, or create a new object and insert into the map. The update is done by a different function that takes a pointer to the object (void update(MyClass *obj)) What is the best way to "insert or update" an element in a map?

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  • Nokogiri (Ruby) and XPath

    - by JP
    Does Nokogiri only support XPath 1.0? I'm trying to do simple string replacement in a value-of cell, like so (where element contains something like '* My string (useless text)') <xsl:value-of select="replace(element,'^\*\ (.+)\ \(.*\)$','\\1')"> Is this poorly formed XSL? Or is there a limitation with Nokogiri?

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  • Can a conforming C# compiler optimize away a local (but unused) variable if it is the only strong re

    - by stakx
    The title says it all, but let me explain: void Case_1() { var weakRef = new WeakReference(new object()); GC.Collect(); // <-- doesn't have to be an explicit call; just assume that // garbage collection would occur at this point. if (weakRef.IsAlive) ... } In this code example, I obviously have to plan for the possibility that the new'ed object is reclaimed by the garbage collector; therefore the if statement. (Note that I'm using weakRef for the sole purpose of checking if the new'ed object is still around.) void Case_2() { var unusedLocalVar = new object(); var weakRef = new WeakReference(unusedLocalVar); GC.Collect(); // <-- doesn't have to be an explicit call; just assume that // garbage collection would occur at this point. Debug.Assert(weakReferenceToUseless.IsAlive); } The main change in this code example from the previous one is that the new'ed object is strongly referenced by a local variable (unusedLocalVar). However, this variable is never used again after the weak reference (weakRef) has been created. Question: Is a conforming C# compiler allowed to optimize the first two lines of Case_2 into those of Case_1 if it sees that unusedLocalVar is only used in one place, namely as an argument to the WeakReference constructor? i.e. is there any possibility that the assertion in Case_2 could ever fail?

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  • C# Reflection: How to call method of interface without creating instance?

    - by jitm
    Hello, I have situation where I have to call method of interface using reflection, like this object x = null; MethodInfo method = interfaceExists.GetMethod("ShutDown"); method.Invoke(x, new object[] { 4 }) As you can see I do not create instance of object! And, as I can supposed, I receive exception Non-static method requires a target And Question, Can I call method of interface using reflection without creating instance of interface and if YES, How I can do it ? Thank you.

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