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  • Better exception for non-exhaustive patterns in case

    - by toofarsideways
    Is there a way to get GHCi to produce better exception messages when it finds at runtime that a call has produced value that does not match the function's pattern matching? It currently gives the line numbers of the function which produced the non-exhaustive pattern match which though helpful at times does require a round of debugging which at times I feel is doing the same set of things over and over. So before I tried to put together a solution I wanted to see if something else exists. An exception message that in addition to giving the line numbers shows what kind of call it attempted to make? Is this even possible?

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  • Best practices for handling unique constraint violation

    - by umesh awasthi
    Hi All, While working in my application i came across a situation in which there are likely chances to Unque Constraints Violation.I have following options Catch the exception and throw it back to UI At UI check for the exception and show approrpriate Error Message This is something different idea is to Check in advance about the existance of the given Unique value before starting the whole operation. My Question is what might be the best practice to handle such situation.Currently we are using combo of Struts2+Spring 3.x+Hibernate 3.x Thanks in advance

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  • Cannot write the output to a text file in cpp program

    - by swapedoc
    I have this input file "https://code.google.com/codejam/contest/351101/dashboard/do/A-large-practice.in?cmd=GetInputFile&problem=374101&input_id=1&filename=A-large-practice.in&redownload_last=1&agent=website&csrfmiddlewaretoken=OWMxNTVmMTUyODBiYjhhN2Q2OTM3ZGJiMTNhNDkwMDF8fDEzNzIxNzI1NTE3ODAzMjA%3D" I tried to read this file :-using freopen("filename.txt",r,stdin); and then I wanted the output written to be written to another text file which I can upload in this codejam practice question for the judge. #include<iostream> #include<cstdio> using namespace std; int main() { int t,k=0,a[2000]; freopen("ab.txt","r",stdin); scanf("%d",&t); while(t--) { freopen("cb.txt","w",stdout); int c; scanf("%d",&c); int n; scanf("%d",&n); for(int i=0;i<n;i++) scanf("%d",&a[i]); printf("Case #%d: ",++k); for(int i=0;i<n-1;i++) {for(int j=i+1;j<n;j++) if((a[i]+a[j])==c) {printf("%d %d\n",i+1,j+1); i=n;} } } return 0; } This is my code. Now the problem is the output file cb.txt contains only the last line of the input. I want the the whole of the output to be written to cb.txt,so what should I do.

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  • OOP - Handling Automated Instances of a Class - PHP

    - by dscher
    This is a topic that, as a beginner to PHP and programming, sort of perplexes me. I'm building a stockmarket website and want users to add their own stocks. I can clearly see the benefit of having each stock be a class instance with all the methods of a class. What I am stumped on is the best way to give that instance a name when I instantiate it. If I have: class Stock() { ....doing stuff..... } what is the best way to give my instances of it a name. Obviously I can write: $newStock = new Stock(); $newStock.getPrice(); or whatever, but if a user adds a stock via the app, where can the name of that instance come from? I guess that there is little harm in always creating a new child with $newStock = new Stock() and then storing that to the DB which leads me to my next question! What would be the best way to retrieve 20 user stocks(for example) into instances of class Stock()? Do I need to instantiate 20 new instances of class Stock() every time the user logs in or is there something I'm missing? I hope someone answers this and more important hope a bunch of people answer this and it somehow helps someone else who is having a hard time wrapping their head around what probably leads to a really elegant solution. Thanks guys!

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  • Should the PHP community start using more descriptive Exceptions?

    - by fireeyedboy
    I work with Zend Framework a lot and I just took a peek at Kohana, and it strikes me as odd that this is a typical scenario in these frameworks: throw Some_Componenents_Exception( 'invalid argument' ); Where I believe this wouldn't be mouch more useful: throw Some_Components_InvalidArgumentException( 'whatever discription' ); Because it is easier to catch. I suspect, but immediately admit it's prejudiced, that the former practice is common in the PHP community. Should we, the PHP community, start using these descriptive types of expections more?

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  • bad performance from too many caught errors?

    - by Christopher Klein
    I have a large project in C# (.NET 2.0) which contains very large chunks of code generated by SubSonic. Is a try-catch like this causing a horrible performance hit? for (int x = 0; x < identifiers.Count; x++) {decimal target = 0; try { target = Convert.ToDecimal(assets[x + identifiers.Count * 2]); // target % } catch { targetEmpty = true; }} What is happening is if the given field that is being passed in is not something that can be converted to a decimal it sets a flag which is then used further along in the record to determine something else. The problem is that the application is literally throwing 10s of thousands of exceptions as I am parsing through 30k records. The process as a whole takes almost 10 minutes for everything and my overall task is to improve that time some and this seemed like easy hanging fruit if its a bad design idea. Any thoughts would be helpful (be kind, its been a miserable day) thanks, Chris

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  • event args assigning

    - by Miroo
    i have this event handler Temp.MouseLeftButtonDown += new MouseButtonEventHandler(Temp_MouseLeftButtonDown); but i wanna send some parameter to access in the Temp_MouseLeftButtonDown function. how can i assign it ??

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  • handling large arrays with array_diff

    - by bigmac
    I have been trying to compare two arrays. Using array_intersect presents no problems. When using array_diff and arrays with ~5,000 values, it works. When I get to ~10,000 values, the script dies when I get to array_diff. Turning on error_reporting did not produce anything. I tried creating my own array_diff function: function manual_array_diff($arraya, $arrayb) { foreach ($arraya as $keya => $valuea) { if (in_array($valuea, $arrayb)) { unset($arraya[$keya]); } } return $arraya; } source: http://stackoverflow.com/questions/2479963/how-does-array-diff-work I would expect it to be less efficient that than the official array_diff, but it can handle arrays of ~10,000. Unfortunately, both array_diffs fail when I get to ~15,000. I tried the same code on a different machine and it runs fine, so it's not an issue with the code or PHP. There must be some limit set somewhere on that particular server. Any idea how I can get around that limit or alter it or just find out what it is?

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  • ASP.NET handling button click event before OnPreInit

    - by Phillykins
    Hello, I have a data access layer, a business logic layer and a presentation layer (ie. the pages themselves). I handle the OnPreInit event and populate collections required for the page. All the data comes from an SQL server database and I do not use caching. I handle a button click event to grab values from a form and insert a new object into the database. The problem is that by the time I handle the click event, the collections have already been populated, so the new item which has been inserted into the database has not been retrieved. What is the accepted solution to this? I could insert the new object directly into the collection and re-bind the GridView, but the SQL query selects only a set of objects and the new object could fall outside of this set. Thanks!

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  • Linq to SQL - Error handling

    - by Sundararajan S
    I have a linq to sql statement that inserts records in the database. If there is a duplicate, it throws Primary key violation . after this happens, whenever i try to execute any other statement, it repeatedly shows this error. Is this a problem of transaction not getting closed. Also how to handle transactions in a more reliable way in LINQ to SQL

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  • C++/MFC: Handling multiple CListCtrl's headers HDN_ITEMCLICK events

    - by raph.amiard
    I'm coding an MFC application in which i have a dialog box with multiple CListCtrls in report view. I want one of them to be sortable. So i handled the HDM_ITEMCLICK event, and everything works just fine .. Except that if i click on the headers of another CListCtrl, it does sort the OTHER CListCtrl, which does look kind of dumb. This is apparently due to the fact that headers have an ID of 0, which make the entry in the message map look like this : ON_NOTIFY(HDN_ITEMCLICK, 0, &Ccreationprogramme::OnHdnItemclickList5) But since all the headers have an id of zero, apparently every header of my dialog sends the message. Is there an easy way around this problem ?

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  • Handling selection and deselection of objects in a user interface

    - by Dennis
    I'm writing a small audio application (in Silverlight, but that's not really relevant I suppose), and I'm a struggling with a problem I've faced before and never solved properly. This time I want to get it right. In the application there is one Arrangement control, which contains several Track controls, and every Track can contain AudioObject controls (these are all custom user controls). The user needs to be able to select audio objects, and when these objects are selected they are rendered differently. I can make this happen by hooking into the MouseDown event of the AudioObject control and setting state accordingly. So far so good, but when an audio object is selected, all other audio objects need to be deselected (well, unless the user holds the shift key). Audio objects don't know about other audio objects though, so they have no way to tell the rest to deselect themselves. Now if I would approach this problem like I did the last time I would pass a reference to the Arrangement control in the constructor of the AudioObject control and give the Arrangement control a DeselectAll() method or something like that, which would tell all Track controls to deselect all their AudioObject controls. This feels wrong, and if I apply this strategy to similar issues I'm afraid I will soon end up with every object having a reference to every other object, creating one big tightly coupled mess. It feels like opening the floodgates for poorly designed code. Is there a better way to handle this?

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  • Redoundant code in exception handling

    - by Nicola Leoni
    Hi, I've a recurrent problem, I don't find an elegant solution to avoid the resource cleaning code duplication: resource allocation: try { f() } catch (...) { resource cleaning code; throw; } resource cleaning code; return rc; So, I know I can do a temporary class with cleaning up destructor, but I don't really like it because it breaks the code flow and I need to give the class the reference to the all stack vars to cleanup, the same problem with a function, and I don't figure out how does not exists an elegant solution to this recurring problem.

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  • WPF - Handling events from user control in View Model

    - by Vitaly
    I’m building a WPF application using MVVM pattern (both are new technologies for me). I use user controls for simple bits of reusable functionality that doesn’t contain business logic, and MVVM pattern to build application logic. Suppose a view contains my user control that fires events, and I want to add an event handler to that event. That event handler should be in the view model of the view, because it contains business logic. The question is – view and the view model are connected only by binding; how do I connect an event handler using binding? Is it even possible (I suspect not)? If not – how should I handle events from a control in the view model? Maybe I should use commands or INotifyPropertyChanged?

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  • Handling exceptions raised in observers

    - by sparky
    I have a Rails (2.3.5) application where there are many groups, and each Group has_many People. I have a Group edit form where users can create new people. When a new person is created, they are sent an email (the email address is user entered on the form). This is accomplished with an observer on the Person model. The problem comes when ActionMailer throws an exception - for example if the domain does not exist. Clearly that cannot be weeded out with a validation. There would seem to be 2 ways to deal with this: A begin...rescue...end block in the observer around the mailer. The problem with this is that the only way to pass any feedback to the user would be to set a global variable - as the observer is out of the MVC flow, I can't even set a flash[:error] there. A rescue_from in the Groups controller. This works fine, but has 2 problems. Firstly, there is no way to know which person threw the exception (all I can get is the 503 exception, no way to know which person caused the problem). This would be useful information to be able to pass back to the user - at the moment, there is no way for me to let them know which email address is the problem - at the moment, I just have to chuck the lot back at them, and issue an unhelpful message saying that one of them is not correct. Secondly (and to a certain extent this make the first point moot) it seems that it is necessary to call a render in the rescue_from, or it dies with a rather bizarre "can't convert Array into String" error from webbrick, with no stack trace & nothing in the log. Thus, I have to throw it back to the user when I come across the first error and have to stop processing the rest of the emails. Neither of the solutions are optimal. It would seem that the only way to get Rails to do what I want is option 1, and loathsome global variables. This would also rely on Rails being single threaded. Can anyone suggest a better solution to this problem?

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  • Adding jQuery event handler to expand div when a link is clicked

    - by hollyb
    I'm using a bit of jQuery to expand/hide some divs. I need to add an event handler so that when a link is clicked, it opens a corrisponding div. Each toggled div will have a unique class assigned to it. I am looking for some advice about how to build the event handler. The jQuery $(document).ready(function(){ $(".toggle_container:not(:first)").hide(); $(".toggle_container:first").show(); $("h6.trigger:first").addClass("active"); $("h6.trigger").click(function(){ $(this).toggleClass("active"); $(this).next(".toggle_container").slideToggle(300); }); The css: // uses a background image with an on (+) and off (-) state stacked on top of each other h6.trigger { background: url(buttonBG.gif) no-repeat;height: 46px;line-height: 46px;width: 300px;font-size: 2em;font-weight: normal;} h6.trigger a {color: #fff;text-decoration: none; display: block;} h6.active {background-position: left bottom;} .toggle_container { overflow: hidden; } .toggle_container .block {padding: 20px;} The html has a list of links, such as: <a href="#">One</a> <a href="#">Two</a> and the coorisponding divs to open: <h6 class="trigger">Container one</h6> <div class="toggle_container"> div one </div> <h6 class="trigger">Container two</h6> <div class="toggle_container Open"> div one </div> As I mentioned, I will be assigning a unique class to facilitate this. Any advice? Thanks! To clarify, i'm looking for some advice to build an event handler to toggle open a specific div when a link is clicked from a different part of the page, from a nav for instance.

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  • How to get the current exception without having passing the variable?

    - by Pierre-Alain Vigeant
    I am looking for a way to retrieve the current exception without having to pass it as a variable. Suppose the following code public void MakeItFail() { try { throw new FailException(); } catch // Yes I'm aware that this shouldn't be done, but I don't want to go through all the code base and change it { ShowMessage("An error occured"); } } public void ShowMessage(string message) { // How can I retrieve the exception here } In the watch window, I can use $exception to get the current exception. Is there is a code equivalent?

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  • Is it possible to programmatically switch error log providers with ELMAH?

    - by Ralph Lavelle
    Is it possible to switch from using the XML provider to SQL Server using ELMAH? I need to investigate this option because of the fallibility of our SQL Server where our ELMAH errors are stored. I want to be able to fail gracefully and continue logging to XML if the server fails. I can see that programmatic connection string switching is possible, and I see that ELMAH Issue 149 announces the programmatic configuration of default error log, but I can't actually see any code examples anywhere, so I'm not too sure if this is possible. I'm guessing it is, in which case does anyone know for sure? My question is similar to this one, except that I want to try and log errors to SQL Server, and if that fails switch to XML, not log to all stores all the time.

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  • php mysql database users connection handling

    - by aviv
    What is the best way to handle mysql database users connection in PHP? I have a web server running a PHP application on MySQL. I have created a database user for the application: dbuser1 with limited access - only for query, insert and update tables. No alter table. Now the question is, should i use the same dbuser1 widely in my scripts, so if there are 100 current people using my system and hence 100 scripts running parallel they all connect to the database with the same dbuser1? or should i create a few users and assign each script a different user or load-balance between the dbusers ?

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  • Handling ID's with db4o and ASP.NET MVC2

    - by Craig McGuff
    So, i'm looking at the TekPub sample for ASP.NET MVC2 (http://mvcstarter.codeplex.com/) using DB4o and there are a bunch of templates to create controllers etc, the generated code looks like: public ActionResult Details(int id) { var item = _session.Single<Account>(x=>x.ID == id); return View(item); } Now, my understanding is that using DB4o or a simliar object database that ID's are not required, so how/what exactly do I pass to enable this kind of templated code to function? UPDATE: Both answers were useful, I have modifed the templates to use GUID as the ID. I will add any relevant code/notes here once I see how it works out.

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  • Handling duplicate nodes in XML

    - by JYelton
    Scenario: I am parsing values from an XML file using C# and have the following method: private static string GetXMLNodeValue(XmlNode basenode, string strNodePath) { if (basenode.SelectSingleNode(strNodePath) != null) return (basenode.SelectSingleNode(strNodePath).InnerText); else return String.Empty; } To get a particular value from the XML file, I generally pass the root node and a path like "parentnode/item" I recently ran into an issue where two nodes at the same document level share the same name. Question: What is the best way to get the values for duplicate-named nodes distinctly? My thought was to load all values matching the node name into an array and then using the array index to refer to them. I'm not sure how to implement that, though. (I'm not well-versed in XML navigation.)

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  • Checked equivalent to IllegalArgumentException?

    - by jv1975oid
    I have a method that takes an enum as a parameter and returns some information dependent on that parameter. However, that enum contains some values which should not be handled, and should raise an error condition. Currently the method throws an IllegalArgumentException but I would like this to be a checked exception to force callers to catch it (and return gracefully, logging an error). Is there something suitable or should I create my own Exception subclass? I'm open to other patterns as well. A reasonable reaction would be that all values of the enum should be handled, but that isn't the case. When a new value is added to the enum, I want to make sure that this method does the right thing - alerting a human is preferable to using some default return value in this case. Thanks for any advice.

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  • How can I dynamically inject code to event handlers in Delphi?

    - by mjustin
    For debugging / performance tests I would like to dynamically add logging code to all event handlers of components of a given type. For example, for all Dataset components located ona TDatamodule, I would like to add some code for the BeforeOpen and the AfterOpen event to store the start and end time and send a line to a logger with the elapsed time in the AfterOpen event. I would prefer to do this dynamically (no component subclassing), so that I can add this to all existing datamodules and forms with minimal effort only when needed. Iterating all components and filtering by their type is easy, but for the components which already have event handlers assigned, I need a way to store the existing event handlers, and assign a new modified event handler which first does the logging and then will invoke the original code which was already present. Is there a design pattern which can be applied, or even some example code which shows how to implement this in Delphi?

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  • Memory section handling error

    - by Basilevs
    I'm getting a link time error: WARNING: /home/gulevich/development/camac-fedorov/camac/linux/k0607-lsi6/camac-k0607-lsi6.o (.ctors): unexpected non-allocatable section. Did you forget to use "ax"/"aw" in a .S file? Note that for example <linux/init.h> contains section definitions for use in .S files. The code causing the error (assembly in C source): # if defined(__ELF__) # define __SECTION_FLAGS ", \"aw\" , @progbits" /* writable flag needed for ld ".[cd]tors" sections bug workaround) */ # elif defined(__COFF__) # define __SECTION_FLAGS ", \"dr\"" /* untested, may be writable flag needed */ # endif asm ( ".section .ctors" __SECTION_FLAGS "\n" ".globl __ctors_begin__\n" "__ctors_begin__:\n" ".previous\n" ); Is there any way to fix this? The idea is to put a varaible __ctors_begin__ at the beginning of a certain memory section. This code is a legacy that worked fine using a different build system and older compiler. Meaning of this assembly code explained in an answer to my previous question.

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