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  • Binary comparison operators on generic types

    - by Brian Triplett
    I have a generic class that takes a type T. Within this class I have a method were I need to compare a type T to another type T such as: public class MyClass<T> { public T MaxValue { // Implimentation for MaxValue } public T MyMethod(T argument) { if(argument > this.MaxValue) { // Then do something } } } The comparison operation inside of MyMethod fails with Compiler Error CS0019. Is it possible to add a constraint to T to make this work? I tried adding a where T: IComparable<T> to the class definition to no avail.

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  • May volatile be in user defined types to help writing thread-safe code

    - by David Rodríguez - dribeas
    I know, it has been made quite clear in a couple of questions/answers before, that volatile is related to the visible state of the c++ memory model and not to multithreading. On the other hand, this article by Alexandrescu uses the volatile keyword not as a runtime feature but rather as a compile time check to force the compiler into failing to accept code that could be not thread safe. In the article the keyword is used more like a required_thread_safety tag than the actual intended use of volatile. Is this (ab)use of volatile appropriate? What possible gotchas may be hidden in the approach? The first thing that comes to mind is added confusion: volatile is not related to thread safety, but by lack of a better tool I could accept it. Basic simplification of the article: If you declare a variable volatile, only volatile member methods can be called on it, so the compiler will block calling code to other methods. Declaring an std::vector instance as volatile will block all uses of the class. Adding a wrapper in the shape of a locking pointer that performs a const_cast to release the volatile requirement, any access through the locking pointer will be allowed. Stealing from the article: template <typename T> class LockingPtr { public: // Constructors/destructors LockingPtr(volatile T& obj, Mutex& mtx) : pObj_(const_cast<T*>(&obj)), pMtx_(&mtx) { mtx.Lock(); } ~LockingPtr() { pMtx_->Unlock(); } // Pointer behavior T& operator*() { return *pObj_; } T* operator->() { return pObj_; } private: T* pObj_; Mutex* pMtx_; LockingPtr(const LockingPtr&); LockingPtr& operator=(const LockingPtr&); }; class SyncBuf { public: void Thread1() { LockingPtr<BufT> lpBuf(buffer_, mtx_); BufT::iterator i = lpBuf->begin(); for (; i != lpBuf->end(); ++i) { // ... use *i ... } } void Thread2(); private: typedef vector<char> BufT; volatile BufT buffer_; Mutex mtx_; // controls access to buffer_ };

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  • Types of PNG image in iPhone app

    - by user297491
    I have an iPhone app that picks images from my internet server. It picks images with png extension but only PNG-24 is workings. The problem is that PNG-24 need some disk space and internet bandwith in iphone. I tried using PNG-8 but the iphone does not recognize it. Someone knows if I have a way to use PNG-8 into my app? Thanks!

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  • javascript textbox call event when value changes

    - by Senica Gonzalez
    I have a textbox, and whenever the value of the box changes, I want to check and see if 20 digits have been entered. I thought that I would use the onChange event, but this seems to be interpreted as the onBlur event on IE. So then I thought I would use onKeyDown, but the problem comes in if the user wants to paste a value into the field, then the function never gets called. There are no other form boxes so I can't rely on onBlur or expect that they will change focus ever. How do I do this? I just want to evaluate the value of the textbox everytime the value of the textbox changes. <input type="text" onKeyDown="myfunction()">

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  • Is it possible to alternate between two types in an XML Schema

    - by lief79
    I'm wondering if I am missing something obvious. I have a list of numbers, possibly including ranges (think of the print page option of a print dialog). Ideally I'd like to have the final XML output look like this, with page and pageRange in an order. <pages> <page> 1</page> <pageRange><start>3</start><end>6</end></pageRange> <page> 34</page> </pages> What would I have to put into a schema to allow this? From what I saw: Sequence with multiple page and page Range allowed doesn't permit alternation. Choice only allows one or the other. I tried messing with all, but I wasn't getting it to validate properly. My short term solution is to have a sequence of ranges, and to force single numbers into the range, but it seems potentially cumbersome. So am I missing something?

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  • Corect syntax to pass get request parameter value by using EL

    - by Stardust
    I'm trying to pass value by using EL expression in get request parameter, but I'm getting empty value of request parameter whenever I click on that URL. Could anyone please tell me the correct syntax? <c:forEach var="message" items="${requestScope.inboxmessage}" varStatus="messageCount" > <a href="just.do?value="+${messageCount.count} > </c:forEach>

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  • Filtering A MySQL Result Set Based On The Return Value Of A Function

    - by Joshua
    I'm a SQL noob, and I need a little bit of help understanding the big picture of if it is possible, and if so how to go about filtering a result set based on the return value of a function which is passed one of the fields of the record. Let's say I have a table called "Numbers" with just one field: "Value". How could I correctly specify the following "pseudo-sql"?: SELECT Value FROM numbers WHERE IsPrime(Value)=true Can I accomplish such a thing, and if so, where/how do I put/store "IsPrime"? I'm using MySQL.

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  • Return/consume dynamic anonymous type across assembly boundaries

    - by friism
    The code below works great. If the Get and Use methods are in different assemblies, the code fails with a RuntimeBinderException. This is because the .Net runtime system only guarantees commonality of anonymous types (<string, int> in this case) within assemblies. Is there any way to fool the runtime system to overcome this? I can expect the object in the debugger on the Use side, and the debugger can see the relevant properties. class Program { static void Main(string[] args) { UsePerson(); Console.ReadLine(); } public static void UsePerson() { var person = GetPerson(); Console.WriteLine(person.Name); } public static dynamic GetPerson() { return new { Name = "Foo", Age = 30 }; } }

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  • Hiding a value in an Android application

    - by Ewan
    Hi, I need to hide a value in a mobile (Android OS) application. As far as I can see, encrypting the value is of no use as the key to the encryption mechanism must be available to the program and is thus available to an attacker reverse-engineering the code. So, it seems that the only "solution" is to hide the secret value in the application as well as possible, obviously not ideal. Any comments? Am I missing something? If not, what's the best way to hide the value? Thanks for your ideas! Ewan

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  • How to introduce custom primitive key types to WCF Data Services (Astoria)

    - by Artem Tikhomirov
    Hello. We use custom type to represent Identifiers in our project. It has TypeConvertor attached and it always helped with serialization. I've tried to use WCF Data Services to expose some data from our system, but faced a problem. Astoria framework do not recognize class as an entity even though I've decorated it with [DataServiceKey("Id")] attribute. If I change type of property to Guid - it totally works :(. How could teach WCF Data Services to understand this simple class?

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  • selected value for dropdownbox in asp.net mvc using selectlist

    - by FosterZ
    hi, i have following selectlist for dropdownbox in aspnet mvc. This is the editEmployee Action controller, so while edit page is displayed i want to display a selectvalue in dropdownbox,since "SelectList" takes 3 parameters one for value,one for text and other is for selected value, here i'm not getting what should i pass in 3rd parameter, coz its asking an object for selected value. ViewData["DepartmentList"] = new SelectList(DepartmentRepository.GetDepartmentsBySchoolIdInList(ViewData["schoolId"].ToString()),"DepartmentId","DepartmentTitle"); here is the view =Html.DropDownList("DepartmentList")

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  • sending a selected value from a dropdownlist to a servlet with xhr

    - by kawtousse
    I am trying to send the clicked value of a dropdown list to my servlet to run a SQL query using the value received. To do it I am using Ajax like that: function showProject(prj) { xmlhttp = GetXmlHttpObject(); if (xmlhttp == null) { alert ("Browser does not support HTTP Request"); return; } var url = "ServletxmlGenerator.java"; idprj = prj.options[prj.selectedIndex].value; url = url + "?idprj=" + idprj; xmlhttp.onreadystatechange = stateChanged; xmlhttp.open("GET",url,true); xmlhttp.send(null); } The servlet when String projectcode=(String) request.getParameter("idprj"); returns null. When I select a value from the JSP that construct the dropdown list and from which the function showProject is handled the same thing is happned. It returns always null. So the parameter(idprj) is not passed anyway. How can I handle with this. I need to send the selected value to the servlet to run my SQL query.

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  • Formatting address of different types

    - by mickyjtwin
    I have various classes which all contain address details, i.e. AddressLine1, AddressLine2, AddressLine3, Suburb, Town, etc. On the front end, I need to format the address in a particular way, i.e. AddressLine1<br /> AddressLine2<br /> Suburb State Postcode If AddressLine2 does not exist or empty, don't show it. Quite straight-forward. I am trying to determine the best way to show this info. At the moment, the Address property of each class calls a FormatAddress method which writes out the html string. This exists as a method of the class. My opinion is that any formatting should exist from the front-end control i.e. ascx etc. However, if these DetailClasses need to format the same address info, what would be the best option, also making it easier to maintain?

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  • create table based on a user defined type

    - by Glen
    Suppose I have a user defined type: CREATE OR REPLACE TYPE TEST_TYPE AS OBJECT ( f1 varchar2(10), f2 number(5) ); Now, I want to create a table to hold these types. I can do the following: create table test_type_table ( test_type_field test_type ); This gives me a table with one column, test_type_field. Is there an easy and automated way to instead create a table such that it has 2 columns, f1 and f2?. So that it's the equivilent to writing: create table test_type_table ( f1 varchar2(10), f2 number(5) );

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  • How to get the Time value from datetime picker

    - by Ranjana
    how to get the time value in a stored procedure form datepicker value i.e i have a datetime picker value stored into my table as '2010-04-06 09:00:00.000' '2010-04-07 14:30:00.000' i have got the date sepeartely using convert(varchar,Date,3) as Date.. i have got the time seperately using convert(time,Time) but it show the values as 9:00 , 14:30 i need it to show as 9.00 am and 2.30pm instead of 14.30. How to achieve this????????? and help??????

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  • Cannot read value from SYS_CONTEXT

    - by AppleGrew
    I have a PL/SQL procedure which sets some variable in user session, like the following:- Dbms_Session.Set_Context( NAMESPACE =>'MY_CTX', ATTRIBUTE => 'FLAG_NAME', Value => 'some value'); Just after this (in the same procedure), I try to read the value of this flag, using:- SYS_CONTEXT('MY_CTX', 'FLAG_NAME'); The above returns nothing. How did the DB lose this value? The weirder part is that if I invoke this proc directly from Oracle SQL Developer then it works. It doesn't work when I invoke this proc from my web application from callable statement. --EDIT-- Added an example as to how we are invoking the proc from our Java code. String statement = "Begin package_name.proc_name( flag_val => :1); END;"; OracleCallableStatement st = <some object by some framework> .createCallableStatement(statement); st.setString(1, 'flag value'); st.execute(); st.close();

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  • Set default value for a input file form

    - by aladine
    Hi, I have an input file HTML form and I want to set the initial value for the file path in an HTML form . I try to change tag "value" but it doesn't work anyway. <input type="file" name="testcase" value= "C:\test.txt"> Please give me some advice for this small problem. Thanks.

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  • Django DecimalField returns "None" instead of empty value

    - by Ed
    Is there a way to force django to display nothing instead of "None" for a Decimal Field that's been left blank? In my template, I show a list of all the values for a particular field. Each value is hyperlinked to a page that displays the results of a query filtered on that value. But because there are some entries with null value, my list includes actual DecimalField entries and "None" for all those that are empty. When a user clicks on None, django throws a validation error because you cannot query a DecimalField using a string. I could write if statements checking all instances of decimal fields for Nones and skipping them, but that is far from an elegant solution. Any advice? This is one part of the code, though there are other templates that derive the None value in slightly different manners: {% for item in choices %} <a href={% url app_views.field_choice item %}>{{ item }}</a><br> {% endfor %}

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  • C++ stack for multiple data types (RPN vector calculator)

    - by Arrieta
    Hello: I have designed a quick and basic vector arithmetic library in C++. I call the program from the command line when I need a rapid cross product, or angle between vectors. I don't use Matlab or Octave or related, because the startup time is larger than the computation time. Again, this is for very basic operations. I am extending this program, and I will make it work as an RPN calculator, for operations of the type: 1 2 3 4 5 6 x out: -3 6 -3 (give one vector, another vector, and the "cross" operator; spit out the cross product) The stack must accept 3d vectors or scalars, for operations like: 1 2 3 2 * out: 2 4 6 The lexer and parser for this mini-calculator are trivial, but I cannot seem to think of a good way for creating the internal stack. How would you create a stack of for containing vectors or doubles (I rolled up my own very simple vector class - less than one hundred lines and it does everything I need). How can I create a simple stack which accepts elements of class Vector or type double? Thank you.

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  • How to get value of a input field in Javascript

    - by gaurav.mishra280295
    I am using valums-file-uploader plugin. It allows me to upload files using ajax. I have a problem with it. I have the following script- <input type="text" id="Gaurav" name="Gaurav" /> <script src="fileuploader.js" type="text/javascript"></script> <script> function createUploader(){ var uploader = new qq.FileUploader({ element: document.getElementById('file'), action: 'do-nothing.php', params:{param: document.getElementById('Gaurav').value}, allowedExtensions: ['jpg', 'jpeg', 'png', 'gif'], minSizeLimit: 1, debug: false }); } // in your app create uploader as soon as the DOM is ready // dont wait for the window to load window.onload = createUploader; </script> In it, I want to set the value of param entered by the user. The code is working properly for default value of Gaurav, but didn't work for user inputted value.

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  • PostgreSQL 8.3 data types: xml vs varchar

    - by Sejanus
    There's xml data type in Postgres, I never used it before so I'd like to hear opinions. Downsides and upsides vs using regular varchar (or Text) column to store xml. The text I'm going to store is xml, well-formed, UTF-8. No need to search by it (I've read searching by xml is slow). This XML actually is data prepared for PDF generation with Apache FOP. XML can be generated dynamically from data found elsewhere (other Postgres tables), it's stored as is only so that I won't need to generate it twice. Kinda backup#2 for already generated PDF documents. Anything else to know? Good practices, performance, maintenance, etc?

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