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  • java packets byte

    - by user303289
    Guys, I am implementing a protocol in one of the wireless project. I am stucked at one point. In of the java file i am suppose to receive a packet and that packet is 12 byte packet and I have to write different functions for reading different parts of packets and convert it to diferent type. Like I want first four byte in one of the function and convert it to int, next two bytes in string. and again next two in string, last two hop in string and followed by last two int. I want follwing function to implement: // here is the interface /* FloodingData should use methods defined in this class. */ class FloodingPacket{ public static void main(String arg[]){ byte FloodingPack[]; // just for example to test in code FloodingPack=new byte[12]; interface IFloodingPacket { // Returns the unique sequence number for the packet int getSequenceNumber() ; // Returns the source address for the packet String getSourceAddress(); // Returns the destination address for the packet String getDestinationAddress(); // Returns the last hop address for the packet String getLastHopAddress(); // Sets the last hop address to the address of the node // which the packet was received from void updateLastHopAddress(); // Returns the entire packet in bytes (for sending) byte[] getBytes(); // Sets the bytes of the packet (for receiving) void setBytes(byte[] packet); }

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  • Call AsyncTask methods from another class/service (callbacks?)

    - by TiGer
    Hi, I was wondering if it's possible to call specific methods defined within the AsynTask class from another class and/or service ? In my specific case I have a Service playing some sounds, but the sound is selected from a List with available sounds... When a sounds is selected it is downloaded from my home server, this takes some time (not much, let's say around the 3-4 seconds, the sounds/effects aren't big in size)... So my problem at the moment is that I have a service to play those sounds, and when I select one I wanted to show a progressdialog... The way (if I understood correctly) is to use an AsyncTask, but the only thing the AsyncTask will do is telling my Service to play a specific sound from my server... So there is no "callback" from the service to the Asynctask... How can I achieve that ? How can I call a running AsyncTask, which sits in another class, and tell him all work is done and thus he can stop showing the ProgressDialog ? Or am I over-engineering it and there are other ways ? Thanks in advance...

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  • Parsing an XML string containing "&#x20;" (which must be preserved)

    - by Zoodor
    I have code that is passed a string containing XML. This XML may contain one or more instances of &#x20; (an entity reference for the blank space character). I have a requirement that these references should not be resolved (i.e. they should not be replaced with an actual space character). Is there any way for me to achieve this? Basically, given a string containing the XML: <pattern value="[A-Z0-9&#x20;]" /> I do not want it to be converted to: <pattern value="[A-Z0-9 ]" /> (What I am actually trying to achieve is to simply take an XML string and write it to a "pretty-printed" file. This is having the side-effect of resolving occurrences of &#x20; in the string to a single space character, which need to be preserved. The reason for this requirement is that the written XML document must conform to an externally-defined specification.) I have tried creating a sub-class of XmlTextReader to read from the XML string and overriding the ResolveEntity() method, but this isn't called. I have also tried assigning a custom XmlResolver.

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  • Windows service (hosting WCF service) stops immediately on start up

    - by Thr33Dii
    My Question: I cannot navigate to the base address once the service is installed because the service won't remain running (stops immediately). Is there anything I need to do on the server or my machine to make the baseAddress valid? Background: I'm trying to learn how to use WCF services hosted in Windows Services. I have read several tutorials on how to accomplish this and it seems very straight forward. I've looked at this MSDN article and built it step-by-step. I can install the service on my machine and on a server, but when I start the service, it stops immediately. I then found this tutorial, which is essentially the same thing, but it contains some clients that consume the WCF service. I downloaded the source code, compiled, installed, but when I started the service, it stopped immediately. Searching SO, I found a possible solution that said to define the baseAddress when instantiating the ServiceHost, but that didnt help either. My serviceHost is defined as: serviceHost = new ServiceHost( typeof( CalculatorService ), new Uri( "http://localhost:8000/ServiceModelSamples/service" ) ); My service name, base address, and endpoint: <service name="Microsoft.ServiceModel.Samples.CalculatorService" behaviorConfiguration="CalculatorServiceBehavior"> <host> <baseAddresses> <add baseAddress="http://localhost:8000/ServiceModelSamples/service"/> </baseAddresses> </host> <endpoint address="" binding="wsHttpBinding" contract="Microsoft.ServiceModel.Samples.ICalculator"/> <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/> </service> I've verified the namespaces are identical. It's just getting frustrating that the tutorials seem to assume that the Windows service will start as long as all the stated steps are followed. I'm missing something and it's probably right in front of me. Please help!

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  • STLifying C++ classes

    - by shambulator
    I'm trying to write a class which contains several std::vectors as data members, and provides a subset of vector's interface to access them: class Mesh { public: private: std::vector<Vector3> positions; std::vector<Vector3> normals; // Several other members along the same lines }; The main thing you can do with a mesh is add positions, normals and other stuff to it. In order to allow an STL-like way of accessing a Mesh (add from arrays, other containers, etc.), I'm toying with the idea of adding methods like this: public: template<class InIter> void AddNormals(InIter first, InIter last); Problem is, from what I understand of templates, these methods will have to be defined in the header file (seems to make sense; without a concrete iterator type, the compiler doesn't know how to generate object code for the obvious implementation of this method). Is this actually a problem? My gut reaction is not to go around sticking huge chunks of code in header files, but my C++ is a little rusty with not much STL experience outside toy examples, and I'm not sure what "acceptable" C++ coding practice is on this. Is there a better way to expose this functionality while retaining an STL-like generic programming flavour? One way would be something like this: (end list) class RestrictedVector<T> { public: RestrictedVector(std::vector<T> wrapped) : wrapped(wrapped) {} template <class InIter> void Add(InIter first, InIter last) { std::copy(first, last, std::back_insert_iterator(wrapped)); } private: std::vector<T> wrapped; }; and then expose instances of these on Mesh instead, but that's starting to reek a little of overengineering :P Any advice is greatly appreciated!

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  • Need Explanation of couchdb reduce function

    - by Alan
    From http://wiki.apache.org/couchdb/Introduction_to_CouchDB_views The couchdb reduce function is defined as function (key, values, rereduce) { return sum(values); } key will be an array whose elements are arrays of the form [key,id] values will be an array of the values emitted for the respective elements in keys i.e. reduce([ [key1,id1], [key2,id2], [key3,id3] ], [value1,value2,value3], false) I am having trouble understanding when/why the array of keys would contain different key values. If the array of keys does contain different key values, how would I deal with it? As an example, assume that my database contains movements between accounts of the form. {"amount":100, "CreditAccount":"account_number", "DebitAccount":"account_number"} I want a view that gives the balance of an account. My map function does: emit( doc.CreditAccount, doc.amount ) emit( doc.DebitAccount, -doc.amount ) My reduce function does: return sum(values); I seem to get the expected results, however I can't reconcile this with the possibility that my reduce function gets different key values. Is my reduce function supposed to group key values first? What kind of result would I return in that case?

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  • Flash Builder 4 "includeIn" property causing design view error

    - by Chris
    I am creating a custom TextInput component that will define an "error" state. I have extended the TextInput class to change the state to "error" if the errorString property's length is greater than 0. In the skin class, I have defined an "error" state, and added some logic to detect the size and position of the error icon. However, if I have this code at the same time I use the "includeIn" property in the bitmap image tag, I get a design view error. If I either A) Only include that code with no "includeIn" property set, it works or B) dont include the code to set the icon size and position and only use the "includeIn" property, it works. Any ideas what could be causing the design view problem when I use both the "includeIn" property and the icon size/position code at the same time? TextInput Class: package classes { import spark.components.TextInput; public class TextInput extends spark.components.TextInput { [SkinState("error")]; public function TextInput() { super(); } override public function set errorString( value:String ):void { super.errorString = value; invalidateSkinState(); } override protected function getCurrentSkinState():String { if (errorString.length>0) { return "error"; } return super.getCurrentSkinState(); } } } TextInput Skin File: override protected function updateDisplayList(unscaledWidth:Number, unscaledHeight:Number):void { //THIS IS THE CODE THAT SEEMS TO BE CAUSING THE PROBLEM if(getStyle("iconSize") == "large") { errorIcon.right = -12; errorIcon.source = new errorIconLg(); } else { errorIcon.right = -5; errorIcon.source = new errorIconSm(); } super.updateDisplayList(unscaledWidth, unscaledHeight); } </fx:Script> <s:states> <s:State name="normal"/> <s:State name="disabled"/> <s:State name="error"/> </s:states> //If I remove the problem code above or if I take out the includeIn //property here, it works <s:BitmapImage id="errorIcon" verticalCenter="0" includeIn="error" /> </s:SparkSkin>

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  • Sending a message to nil?

    - by Ryan Delucchi
    As a Java developer who is reading Apple's Objective-C 2.0 documentation: I wonder as to what sending a message to nil means - let alone how it is actually useful. Taking an excerpt from the documentation: There are several patterns in Cocoa that take advantage of this fact. The value returned from a message to nil may also be valid: If the method returns an object, any pointer type, any integer scalar of size less than or equal to sizeof(void*), a float, a double, a long double, or a long long, then a message sent to nil returns 0. If the method returns a struct, as defined by the Mac OS X ABI Function Call Guide to be returned in registers, then a message sent to nil returns 0.0 for every field in the data structure. Other struct data types will not be filled with zeros. If the method returns anything other than the aforementioned value types the return value of a message sent to nil is undefined. Has Java rendered my brain incapable of grokking the explanation above? Or is there something that I am missing that would make this as clear as glass? Note: Yes, I do get the idea of messages/receivers in Objective-C, I am simply confused about a receiver that happens to be nil.

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  • Prototype or jQuery for DOM manipulation (client-side dynamic content)

    - by luiggitama
    I need to know which of these two JavaScript frameworks is better for client-side dynamic content modification for known DOM elements (by id), in terms of performance, memory usage, etc.: Prototype's $('id').update(content) jQuery's jQuery('#id').html(content) BTW, both libraries coexist with no conflict in my app, because I'm using RichFaces for JSF development, that's why I can use "jQuery" instead of "$". I have at least 20 updatable areas in my page, and for each one I prepare content (tables, option lists, etc.), based on some user-defined client-side criteria filtering or some AJAX event, etc., like this: var html = []; int idx = 0; ... html[idx++] = '<tr><td class="cell"><span class="link" title="View" onclick="myFunction('; html[idx++] = param; html[idx++] = ')"></span>'; html[idx++] = someText; html[idx++] = '</td></tr>'; ... So here comes the question, which is better to use: // Prototype's $('myId').update(html.join('')); // or jQuery's jQuery('#myId').html(html.join('')); Other needed functions are hide() and show(), which are present in both frameworks. Which is better? Also I'm needing to enable/disable form controls, and to read/set their values. Note that I know my updatable area's id (I don't need CSS selectors at this point). And I must tell that I'm saving these queried objects in some data structure for later use, so they are requested just once when the page is rendered, like this: MyData = {div1:jQuery('#id1'), div2:$('id2'), ...}; ... div1.update('content 1'); div2.html('content 2'); So, which is the best practice?

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  • Best loose way to get objects with common base class

    - by Michael Teper
    I struggled to come up with a good title for this question, so suggestions are welcome. Let's say we have an abstract base class ActionBase that looks something like this: public abstract class ActionBase { public abstract string Name { get; } public abstract string Description { get; } // rest of declaration follows } And we have a bunch of different actions defined, like a MoveFileAction, WriteToRegistryAction, etc. These actions get attached to Worker objects: public class Worker { private IList<ActionBase> _actions = new List<ActionBase>(); public IList<ActionBase> Actions { get { return _actions; } } // worker stuff ... } So far, pretty straight-forward. Now, I'd like to have a UI for setting up Workers, assigning Actions, setting properties, and so on. In this UI, I want to present a list of all available actions, along with their properties, and for that I'd want to first gather up all the names and descriptions of available actions (plus the type) into a collection of the following type of item: public class ActionDescriptor { public string Name { get; } public string Description { get; } poblic Type Type { get; } } Certainly, I can use reflection to do this, but is there a better way? Having Name and Description be instance properties of ActionBase (as opposed to statics on derived classes) smells a bit, but there isn't an abstract static in C#. Thank you!

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  • Can anyone explain this impossible bit of PHP logic?

    - by user268208
    I'm attempting to debug a simple PHP script. Essentially, there's a variable which is defined with: $variable = ($_GET['variable'] == 'true') ? TRUE : FALSE; Then, in the view file, the following code is meant to display a box if $variable == TRUE: <? if ($variable == true) { ?> <p class="box">You have imported a new plan.</p> <? } ?> Now, even when that $variable, as shown by var_dump($variable); == FALSE, that HTML is printed between the if { } tags. To me, this defies logic. I simply can't figure out this problem out. Furthermore, this code works fine on many PHP4 and PHP5 installations except for one particular server running PHP5.2. Any possible suggestions? Leads? I'm pulling out my hair trying to figure this one out. Thank you.

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  • Class Inside Structure

    - by Knvn
    Could some one please explain, What happens when a reference type is defined inside the value type. I write the following code: namespace ClassInsideStruct { class ClassInsideStruct { static void Main(string[] args) { ValueType ObjVal = new ValueType(10); ObjVal.Display(); ValueType.ReferenceType ObjValRef = new ValueType.ReferenceType(10); ObjValRef.Display(); Test(ObjVal, ObjValRef); ObjVal.Display(); ObjValRef.Display(); Console.ReadKey(); } private static void Test(ValueType v, ValueType.ReferenceType r) { v.SValue = 50; r.RValue = 50; } } struct ValueType { int StructNum; ReferenceType ObjRef; public ValueType(int i) { StructNum = i; ObjRef = new ReferenceType(i); } public int SValue { get { return StructNum; } set { StructNum = value; ObjRef.RValue = value; } } public void Display() { Console.WriteLine("ValueType: " + StructNum); Console.Write("ReferenceType Inside ValueType Instance: "); ObjRef.Display(); } public class ReferenceType { int ClassNum; public ReferenceType(int i) { ClassNum = i; } public void Display() { Console.WriteLine("Reference Type: " + ClassNum); } public int RValue { get { return ClassNum; } set { ClassNum = value; } } } } } Which outputs: ValueType: 10 ReferenceType Inside ValueType Instance: Reference Type: 10 Reference Type: 10 ValueType: 10 ReferenceType Inside ValueType Instance: Reference Type: 50 Reference Type: 50 I'm curious to know, after calling the method Test(ObjVal, ObjValRef), how the values of ReferenceType is changed to 50 which resides inside the ValueType who's value is not changed?

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  • Moq basic questions

    - by devoured elysium
    I made the following test for my class: var mock = new Mock<IRandomNumberGenerator>(); mock.Setup(framework => framework.Generate(0, 50)) .Returns(7.0); var rnac = new RandomNumberAverageCounter(mock.Object, 1, 100); rnac.Run(); double result = rnac.GetAverage(); Assert.AreEqual(result, 7.0, 0.1); The problem here was that I changed my mind about what range of values Generate(int min, int max) would use. So in Mock.Setup() I defined the range as from 0 to 50 while later I actually called the Generate() method with a range from 1 to 100. I ran the test and it failed. I know that that is what it's supposed to happen but I was left wondering if isn't there a way to launch an exception or throw in a message when trying to run the method with wrong params. Also, if I want to run this Generate() method 10 times with different values (let's say, from 1 to 10), will I have to make 10 mock setups or something, or is there a special method for it? The best I could think of is this (which isn't bad, I'm just asking if there is other better way): for (int i = 1; i < 10; ++i) { mock.Setup(framework => framework.Generate(1, 100)) .Returns((double)i); }

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  • Use external inline script as local function

    - by Aidan
    Had this closed once as a duplicate, yet the so-called duplicate DID NOT actually address my whole question. I have found this script that, when run inline, returns your IP. <script type="text/javascript" src="http://l2.io/ip.js"></script> http://l2.io/ip.js Has nothing more than a line of code that says document.write('123.123.123.123'); (But obviously with the user's IP address) I want to use this IP address as a return string for a function DEFINED EXTERNALLY, BUT STILL ON MY DOMAIN. That is, I have a "scripts.js" that contains all the scripts I wish to use, and I would like to include it in that list as a local function that calls to the 12.io function, but javascript won't allow the < tags, so I am unsure as to how to do this. I.e. function getIP() { return (THAT SCRIPT'S OUTPUT); } This is the topic this was supposedly a duplicate of, and it is very similar. Get ip address with javascript However, this DOES NOT address defining as a forwarded script it in my own script file.

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  • SQL Server 2008 - Update a temporary table

    - by user336786
    Hello, I have stored procedure in which I am trying to retrieve the last ticket completed by each user listed in a comma-delimited string of usernames. The user may not have a ticket associated with them, in this case I know that i just need to return null. The two tables that I am working with are defined as follows: User ---- UserName, FirstName, LastName Ticket ------ ID, CompletionDateTime, AssignedTo, AssignmentDate, StatusID TicketStatus ------------ ID, Comments I have created a stored procedure in which I am trying to return the last completed ticket for a comma-delimited list of usernames. Each record needs to include the comments associated with it. Currently, I'm trying the following: CREATE TABLE #Tickets ( [UserName] nvarchar(256), [FirstName] nvarchar(256), [LastName] nvarchar(256), [TicketID] int, [DateCompleted] datetime, [Comments] text ) -- This variable is actually passed into the procedure DECLARE @userList NVARCHAR(max) SET @userList='user1,user2,user2' -- Obtain the user information for each user INSERT INTO #Tickets ( [UserName], [FirstName], [LastName] ) SELECT u.[UserName], u.[FirstName], u.[LastName] FROM User u INNER JOIN dbo.ConvertCsvToTable(@userList) l ON u.UserName=l.item At this point, I have the username, first and last name for each user passed in. However, I do not know how to actually get the last ticket completed for each of these users. How do I do this? I believe I should be updating the temp table I have created. At the same time, id do not know how to get just the last record in an update statement. Thank you!

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  • Make All Types Constant by Default in C++

    - by Jon Purdy
    What is the simplest and least obtrusive way to indicate to the compiler, whether by means of compiler options, #defines, typedefs, or templates, that every time I say T, I really mean T const? I would prefer not to make use of an external preprocessor. Since I don't use the mutable keyword, that would be acceptable to repurpose to indicate mutable state. Potential (suboptimal) solutions so far: // I presume redefinition of keywords is implementation-defined or illegal. #define int int const #define ptr * const int i(0); int ptr j(&i); typedef int const Int; typedef int const* const Intp; Int i(0); Intp j(&i); template<class T> struct C { typedef T const type; typedef T const* const ptr; }; C<int>::type i(0); C<int>::ptr j(&i);

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  • ASP.NET configuration inheritance

    - by NowYouHaveTwoProblems
    I have an ASP.NET application that defines a custom configuration section in web.config. Recently I had a customer who wanted to deploy two instances of the application (for testing in addition to an existing production application). The configuration chosen by the customer was: foo.com - production application foo.com/Testing - test application In this case, the ASP.NET configuration engine decided to apply the settings at foo.com/web.config to foo.com/Testing/web.config. Thankfully this caused a configuration error because the section was redefined at the second level rather than giving the false impression that the two web applications were isolated. What I would like to do is to specify that my configuration section is not inherited and must be re-defined for any web application that requires it but I haven't been able to find a way to do this. My web.config ends up something like this <configuration> <configSections> <section name="MyApp" type="MyApp.ConfigurationSection"/> </configSections> <MyApp setting="value" /> <NestedSettingCollection> <Item key="SomeKey" value="SomeValue" /> <Item key="SomeOtherKey" value="SomeOtherValue" /> </NestedSettingCollection> </MyApp> </configuration>

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  • I need help with a SQL query. Fetching an entry, it's most recent revision and it's fields.

    - by Tigger ate my dad
    Hi there, I'm building a CMS for my own needs, and finished planning my database layout. Basically I am abstracting all possible data-models into "sections" and all entries into one table. The final layout is as follows: Database diagram: I have yet to be allowed to post images, so here is a link to a diagram of my database. Entries (section_entries) are children of their section (sections). I save all edits to the entries in a new revision (section_entries_revisions), and also track revisions on the sections (section_revisions), in order to match the values of a revision, to the fields of the section that existed when the entry-revision was made. The section-revisions can have a number of fields (section_revision_fields) that define the attributes of entries in the section. There is a many-to-many relationship between the fields (section_revision_fields) and the entry-revisions (section_entry_revisions), that stores the values of the attributes defined by the section revision. Feel free to ask questions if the diagram is confusing. Now, this is the most complex SQL I've ever worked with, and the task of fetching my data is a little daunting. Basically what i want help with, is fetching an entry, when the only known variables are; section_id, section_entry_id. The query should fetch the most recent revision of that entry, and the section_revision model corresponding to section_revision_id in the section_entry_revisions table. It should also fetch the values of the fields in the section-revision. I was hoping for a query result, where there would be as many rows as fields in the section. Each row would contain the information of the entry and the section, and then information for one of the fields (e.g. each row corresponding to a field and it's value). I tried to explain the best I could. Again, feel free to ask questions if my description somehow lacking. I hope someone is up for the challenge. Best regards. :-)

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  • Enums and inheritance

    - by devoured elysium
    I will use (again) the following class hierarchy: Event and all the following classes inherit from Event: SportEventType1 SportEventType2 SportEventType3 SportEventType4 I have originally designed the Event class like this: public abstract class Event { public abstract EventType EventType { get; } public DateTime Time { get; protected set; } protected Event(DateTime time) { Time = time; } } with EventType being defined as: public enum EventType { Sport1, Sport2, Sport3, Sport4 } The original idea would be that each SportEventTypeX class would set its correct EventType. Now that I think of it, I think this approach is totally incorrect for two reasons: If I want to later add a new SportEventType class I will have to modify the enum If I later decide to remove one SportEventType that I feel I won't use I'm also in big trouble with the enum. I have a class variable in the Event class that makes, afterall, assumptions about the kind of classes that will inherit from it, which kinda defeats the purpose of inheritance. How would you solve this kind of situation? Define in the Event class an abstract "Description" property, having each child class implement it? Having an Attribute(Annotation in Java!) set its Description variable instead? What would be the pros/cons of having a class variable instead of attribute/annotation in this case? Is there any other more elegant solution out there? Thanks

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  • Set all nonzero matrix elements to 1 (while keeping the others 0)

    - by Tomas Lycken
    I have a mesh grid defined as [X, Y, Z] = meshgrid(-100:100, -100:100, 25); % z will have more values later and two shapes (ovals, in this case): x_offset_1 = 40; x_offset_2 = -x_offset_1; o1 = ((X-x_offset_1).^2./(2*Z).^2+Y.^2./Z.^2 <= 1); o2 = ((X-x_offset_2).^2./(2*Z).^2+Y.^2./Z.^2 <= 1); Now, I want to find all points that are nonzero in either oval. I tried union = o1+o2; but since I simply add them, the overlapping region will have a value of 2 instead of the desired 1. How can I set all nonzero entries in the matrix to 1, regardless of their previous value? (I tried normalized_union = union./union;, but then I end up with NaN in all 0 elements because I'm dividing by zero...) Follow-up question: I got a perfect answer to my original question, but now I have a follow-up question on the same problem. I'm going to define a filled disc, c = (X.^2+Y.^2<R^2) that will also overlap with the two ovals. How do I find all the points that are inside the circle, but not inside any of the ovals?

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  • Template function overloading with identical signatures, why does this work?

    - by user1843978
    Minimal program: #include <stdio.h> #include <type_traits> template<typename S, typename T> int foo(typename T::type s) { return 1; } template<typename S, typename T> int foo(S s) { return 2; } int main(int argc, char* argv[]) { int x = 3; printf("%d\n", foo<int, std::enable_if<true, int>>(x)); return 0; } output: 1 Why doesn't this give a compile error? When the template code is generated, wouldn't the functions int foo(typename T::type search) and int foo(S& search) have the same signature? If you change the template function signatures a little bit, it still works (as I would expect given the example above): template<typename S, typename T> void foo(typename T::type s) { printf("a\n"); } template<typename S, typename T> void foo(S s) { printf("b\n"); } Yet this doesn't and yet the only difference is that one has an int signature and the other is defined by the first template parameter. template<typename T> void foo(typename T::type s) { printf("a\n"); } template<typename T> void foo(int s) { printf("b\n"); } I'm using code similar to this for a project I'm working on and I'm afraid that there's a subtly to the language that I'm not understanding that will cause some undefined behavior in certain cases. I should also mention that it does compile on both Clang and in VS11 so I don't think it's just a compiler bug.

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  • Not getting concept of null

    - by appu
    Hy Guys, Beginning with mysql. I am not able to grasp the concept of NULL. Check screen-shot (*declare_not_null, link*). In it when I specifically declared 'name' field to be NOT NULL. When i run the 'desc test' table command, the table description shows default value for name field to be NULL.Why is that so? From what I have read about NULL, it connotes a missing or information that is not applicable. So when I declare a field to be NOT NULL it implies (as per my understanding) that user must enter a value for the name field else the DB engine should generate an error i.e. record will not be entered in DB. However when i run 'insert into test value();' the DB engine enters the record in table. Check screen-shot(*empty_value, link*). FLICKR LINKS *declare_not_null* http://www.flickr.com/photos/55097319@N03/5302758813/ *empty_values* Check the second screenshot on flickr Q.2 what would be sql statemetn to drop a primary key from a table's field. If I use 'ALTER TABLE test drop key id;' it gives the following: ERROR: Incorrect table definition; there can be only one auto column and it must be defined as a key. Thanks for your help..

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  • Is re-throwing an exception legal in a nested 'try'?

    - by Alexander Gessler
    Is the following well-defined in C++, or not? I am forced to 'convert' exceptions to return codes (the API in question is used by many C users, so I need to make sure all C++ exceptions are caught & handled before control is returned to the caller). enum ErrorCode {…}; ErrorCode dispatcher() { try { throw; } catch (std::bad_alloc&) { return ErrorCode_OutOfMemory; } catch (std::logic_error&) { return ErrorCode_LogicError; } catch (myownstdexcderivedclass&) { return ErrorCode_42; } catch(...) { return ErrorCode_UnknownWeWillAllDie; } } ErrorCode apifunc() { try { // foo() might throw anything foo(); } catch(...) { // dispatcher rethrows the exception and does fine-grained handling return dispatcher(); } return ErrorCode_Fine; } ErrorCode apifunc2() { try { // bar() might throw anything bar(); } catch(...) { return dispatcher(); } return ErrorCode_Fine; } I hope the sample shows my intention. My guess is that this is undefined behaviour, but I'm not sure. Please provide quotes from the standard, if applicable. Alternative approaches are appreciated as well. Thanks!

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  • Destroy? Delete? What's going on here? Rails 2.3.5

    - by Steve
    I am new to rails. My rails version is 2.3.5. I found usage like: In controller, a destroy method is defined and in view, you can use :action = "delete" to fire that method. Isn't the action name has to be the same as the method name? Why delete is mapped to destroy? Again, in my controller, I define a method called destroy to delete a record. In a view, I have <%= link_to "remove", :action = 'destroy', :id = myrecord %. But it never works in practice. Every time I press the remove link, it redirects me to the show view, showing the record's content. I am pretty sure that my destroy method is: def destroy @myobject = MyObject.find(params[:id]) @myobject.destroy @redirect_to :action = 'index' end If I change the method name from destroy to something like remove_me and change the action name to remove_me in the view, everything works as expected. In the above two wired problems, I am sure there is no tricky rountting set in my configuration. All in all, seems the destroy and delete are mysterious keywords in rails. Anyone can explain this to me? Thank you very much.

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  • Macro not declared in this scope

    - by NmdMystery
    I'm using a preprocessor #define macro to count the number of functions in a header file: #define __INDEX -1 //First group of functions void func1(void); #define __FUNC1_INDEX __INDEX + 1 void func2(void); #define __FUNC2_INDEX __FUNC1_INDEX + 1 #undef __INDEX #define __INDEX __FUNC2_INDEX //Second group of functions void func3(void); #define __FUNC3_INDEX __INDEX + 1 void func4(void); #define __FUNC4_INDEX __FUNC3_INDEX + 1 #undef __INDEX #define __INDEX __FUNC4_INDEX //Third group of functions void func5(void); #define __FUNC5_INDEX __INDEX + 1 void func6(void); #define __FUNC6_INDEX __FUNC5_INDEX + 1 #undef __INDEX #define __INDEX __FUNC6_INDEX #define __NUM_FUNCTIONS __INDEX + 1 The preprocessor gets through the first two sets of functions just fine, but when it reaches the line: #define __FUNC5_INDEX __INDEX + 1 I get a "not defined in this scope" error for __INDEX. What makes this really confusing is the fact that the same exact thing is done [successfully] in the second group of functions; __FUNC3_INDEX takes on the value of __INDEX + 1. There's no typos anywhere, as far as I can tell... what's the problem? I'm using g++ 4.8.

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