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• How to fix this java.lang.LinkageError?

  - by Péter Török

  I am trying to configure a custom layout class to Log4J as described in my previous post. The class uses java.util.regex.Matcher to identify potential credit card numbers in log messages. It works perfectly in unit tests (I can also programmatically configure a logger to use it and produce the expected output). However when I try to deploy it with our app in JBoss, I get the following error: --- MBEANS THAT ARE THE ROOT CAUSE OF THE PROBLEM --- ObjectName: jboss.web.deployment:war=MyWebApp-2010_02-SNAPSHOT.war,id=476602902 State: FAILED Reason: java.lang.LinkageError: java/util/regex/Matcher I couldn't even find any info on this form of the error - typically LinkageError seems to show up with a "loader constrain violation" message, like in here. Technical details: we use JBoss 4.2, Java 5, Log4J 1.2.12. We deploy our app in an .ear, which contains (among others) the above mentioned .war file, and the custom layout class in a separate jar file. We override the default settings in jboss-log4J.xml with our own log4j.properties located in a different folder, which is added to the classpath at startup, and is provided via Carbon. I can only guess: are two different Matcher class versions loaded from somewhere, or is Matcher loaded by two different classloaders when it is used from the jar and the war? What does this error message mean, and how can I fix it?

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• Noob question about a statement in a Java program

  - by happysoul

  I am beginner to java and was trying out this code puzzle from the book head first java which I solved as follows and got the output correct :D class DrumKit { boolean topHat=true; boolean snare=true; void playSnare() { System.out.println("bang bang ba-bang"); } void playTopHat() { System.out.println("ding ding da-ding"); } } public class DrumKitTestDriver { public static void main(String[] args) { DrumKit d =new DrumKit(); if(d.snare==true) { d.playSnare(); } d.playTopHat(); } } Output is :: bang bang ba-bang ding ding da-ding Now the problem is that in that code puzzle one code snippet is left that I did not include..it's as follows d.snare=false; Even though I did not write it , I got the output like the book. I am wondering why is there need for us to set it's value as false even when we know the code is gonna run without it too !?? I am wondering what the coder had in mind ..I mean what could be the possible future use and motive behind doing this ? I am sorry if it's a dumb question. I just wanna know why or why not to include that particular statement ? It's not like there's a loop or something that we need to come out of. Why is that statement there ?

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• Java resource closing

  - by Bob

  Hi, I'm writing an app that connect to a website and read one line from it. I do it like this: try{ URLConnection connection = new URL("www.example.com").openConnection(); BufferedReader rd = new BufferedReader(new InputStreamReader(connection.getInputStream())); String response = rd.readLine(); rd.close(); }catch (Exception e) { //exception handling } Is it good? I mean, I close the BufferedReader in the last line, but I do not close the InputStreamReader. Should I create a standalone InputStreamReader from the connection.getInputStream, and a BufferedReader from the standalone InputStreamReader, than close all the two readers? I think it will be better to place the closing methods in the finally block like this: InputStreamReader isr = null; BufferedReader br = null; try{ URLConnection connection = new URL("www.example.com").openConnection(); isr = new InputStreamReader(connection.getInputStream()); br = new BufferedReader(isr); String response = br.readLine(); }catch (Exception e) { //exception handling }finally{ br.close(); isr.close(); } But it is ugly, because the closing methods can throw exception, so I have to handle or throw it. Which solution is better? Or what would be the best solution?

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• cannot override a concrete member without a third member that's overridden by both

  - by huynhjl

  What does the following error message mean? cannot override a concrete member without a third member that's overridden by both (this rule is designed to prevent ``accidental overrides''); I was trying to do stackable trait modifications. It's a little bit after the fact since I already have a hierarchy in place and I'm trying to modify the behavior without having to rewrite a lot of code. I have a base class called AbstractProcessor that defines an abstract method sort of like this: class AbstractProcessor { def onPush(i:Info): Unit } I have a couple existing traits, to implement different onPush behaviors. trait Pass1 { def onPush(i:Info): Unit = { ... } } trait Pass2 { def onPush(i:Info): Unit = { ... } } So that allows me to use new AbstractProcessor with Pass1 or new AbstractProcessor with Pass2. Now I would like to do some processing before and after the onPush call in Pass1 and Pass2 while minimizing code changes to AbstractProcessor and Pass1 and Pass2. I thought of creating a trait that does something like this: trait Custom extends AbstractProcessor { abstract override def onPush(i:Info): Unit = { // do stuff before super.onPush(i) // do stuff after } And using it with new AbstractProcessor with Pass1 with Custom and I got that error message.

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• Does using ReadDirectoryChangesW require administrator rights?

  - by Alex Jenter

  The MSDN says that using ReadDirectoryChangesW implies the calling process having the Backup and Restore priviliges. Does this mean that only process launched under administrator account will work correctly? I've tried the following code, it fails to enable the required privileges when running as a restricted user. void enablePrivileges() { enablePrivilege(SE_BACKUP_NAME); enablePrivilege(SE_RESTORE_NAME); } void enablePrivilege(LPCTSTR name) { HANDLE hToken; DWORD status; if (::OpenProcessToken(::GetCurrentProcess(), TOKEN_ADJUST_PRIVILEGES, &hToken)) { TOKEN_PRIVILEGES tp = { 1 }; if( ::LookupPrivilegeValue(NULL, name, &tp.Privileges[0].Luid) ) { tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED; BOOL result = ::AdjustTokenPrivileges(hToken, FALSE, &tp, 0, NULL, NULL); verify (result != FALSE); status = ::GetLastError(); } ::CloseHandle(hToken); } } Am I doing something wrong? Is there any workaround for using ReadDirectoryChangesW from a non-administrator user account? It seems that the .NET's FileSystemWatcher can do this. Thanks!

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• rich suggestions - why input is null? (seam framework)

  - by Cristian Boariu

  Hi, I'm trying to build a rich suggestions and i do not understand WHY the input value is null... I mean, why inputText value is not taken when i enter something. The .xhtml code: <h:inputText value="#{suggestion.input}" id="text"> </h:inputText> <rich:suggestionbox id="suggestionBoxId" for="text" tokens=",[]" suggestionAction="#{suggestion.getSimilarSpacePaths()}" var="result" fetchValue="#{result.path}" first="0" minChars="2" nothingLabel="No similar space paths found" columnClasses="center" > <h:column> <h:outputText value="#{result.path}" style="font-style:italic"/> </h:column> </rich:suggestionbox> and action class: @Name("suggestion") @Scope(ScopeType.CONVERSATION) public class Suggestion { @In protected EntityManager entityManager; private String input; public String getInput() { return input; } public void setInput(final String input) { this.input = input; } public List<Space> getSimilarSpacePaths() { List<Space> suggestionsList = new ArrayList<Space>(); if (!StringUtils.isEmpty(input) && !input.equals("/")) { final Query query = entityManager.createNamedQuery("SpaceByPathLike"); query.setParameter("path", input + '%'); suggestionsList = (List<Space>) query.getResultList(); } return suggestionsList; } } So, input beeing null, suggestionList is always empty... Why input's value is not posted?

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• Problem with Deploying a ASP.NET MVC Project on a IIS 7.0. BadImageFormatException

  - by Markus

  Hello world, I am stuck with my web application. As known from the title its a ASP.NET MVC(1,0) application so i do the only 2 things that a needed do deploy a application like this. I made a build an copied it to the IIS Folder. In the IDE (VS2008) all works fine :(. This worked a long time. But know i get a error for my included dll of a other project. (I have a German version so the Error is Translated from google sry for that) BadImageFormatException: File or assembly 'DataService.WebInterface.BusinessLogic "or one of its dependencies was not found. An attempt was made to load a file with an incorrect format.] System.Reflection.Assembly._nLoad (AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark & stackMark, throwOnFileNotFound Boolean, Boolean forIntrospection) +0 System.Reflection.Assembly.InternalLoad (AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark & stackMark, Boolean forIntrospection) +416 System.Reflection.Assembly.InternalLoad (String String assemblyName, Evidence assemblySecurity, StackCrawlMark & stackMark, Boolean forIntrospection) +166 System.Reflection.Assembly.Load (String string assemblyName) +35 System.Web.Configuration.CompilationSection.LoadAssemblyHelper (String assemblyName, Boolean starDirective) +190 What does that mean? Is the File corrupted or do i have to change the web.config? Thank your for your support!

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• why unsigned int 0xFFFFFFFF is equal to int -1?

  - by conejoroy

  perhaps it's a very stupid question but I'm having a hard time figuring this out =) in C or C++ it is said that the maximum number a size_t (an unsigned int data type) can hold is the same as casting -1 to that data type. for example see http://stackoverflow.com/questions/1420982/invalid-value-for-sizet Why?? I'm confused.. I mean, (talking about 32 bit ints) AFAIK the most significant bit holds the sign in a signed data type (that is, bit 0x80000000 to form a negative number). then, 1 is 0x00000001.. 0x7FFFFFFFF is the greatest positive number a int data type can hold. then, AFAIK the binary representation of -1 int should be 0x80000001 (perhaps I'm wrong). why/how this binary value is converted to anything completely different (0xFFFFFFFF) when casting ints to unsigned?? or.. how is it possible to form a binary -1 out of 0xFFFFFFFF? I have no doubt that in C: ((unsigned int)-1) == 0xFFFFFFFF or ((int)0xFFFFFFFF) == -1 is equally true than 1 + 1 == 2, I'm just wondering why. thanks!

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• Configure Windows firewall to prevent an application from listening on a specific port [closed]

  - by U-D13

  The issue: there are many applications struggling to listen on port 80 (Skype, Teamviewer et al.), and to many of them that even is not essential (in the sense that you can have a httpd running and blocking the http port, and the other application won't even squeak about being unable to open the port). What makes things worse, some of the apps are... Well, I suppose, that it's okay that the mentally impaired are being integrated in the society by giving them a job to do, but... Programming requires some intellectual effort, in my humble opinion... What I mean is that there is no way to configure the app not to use specific ports (that's what you get for using proprietary software) - you can either add it to windows firewall exceptions (and succumb to undesired port opening behavior) or not (and risk losing most - if not all - of the functionality). Technically, it is not impossible for the firewall to deny an application opening an incoming port even if the application is in the exception list. And if this functionality is built into the Windows firewall somewhere, there should be a way to activate it. So, what I want to know is: whether there exists such an option, and if it does how to activate it.

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• python histogram one-liner

  - by mykhal

  there are many ways, how to code histogram in Python. by histogram, i mean function, counting objects in an interable, resulting in the count table (i.e. dict). e.g.: >>> L = 'abracadabra' >>> histogram(L) {'a': 5, 'b': 2, 'c': 1, 'd': 1, 'r': 2} it can be written like this: def histogram(L): d = {} for x in L: if x in d: d[x] += 1 else: d[x] = 1 return d ..however, there are much less ways, how do this in a single expression. if we had "dict comprehensions" in python, we would write: >>> { x: L.count(x) for x in set(L) } but we don't have them, so we have to write: >>> dict([(x, L.count(x)) for x in set(L)]) however, this approach may yet be readable, but is not efficient - L is walked-through multiple times, so this won't work for single-life generators.. the function should iterate well also through gen(), where: def gen(): for x in L: yield x we can go with reduce (R.I.P.): >>> reduce(lambda d,x: dict(d, x=d.get(x,0)+1), L, {}) # wrong! oops, does not work, the key name is 'x', not x :( i ended with: >>> reduce(lambda d,x: dict(d.items() + [(x, d.get(x, 0)+1)]), L, {}) (in py3k, we would have to write list(d.items()) instead of d.items(), but it's hypothethical, since there is no reduce there) please beat me with a better one-liner, more readable! ;)

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• Form values in a list item

  - by Tri

  Here is the site mock-up I'm working on for my job: http://dev.arm.gov/~noensie/dqhands/cgi-bin/explorer. I'm still a novice in web developing and I need help with placing form values in a list item to pass on to another page. I'd rather not go in great detail the purpose of this website, but in terms of its basic use, select the parameters in the middle column for a request and add it to the list on the right column by pressing on "add request" button when it appears. After the list have been populated, a user would submit the selected requests, which will direct them to another page based on the requests selected (or added to the list, same thing). That last sentence is where I'm having a problem. Right now, each of request in the list in the right column are <li> elements and I assign them attribute values that needed to be passed on to the next page. I tried inserting a hidden input with same values, but I'm still not sure how to utilize that; I'm not even sure using the hidden input is the correct way. Also the "submit request" button is located outside the <form> block. I was going to utilize javascript and jQuery to enable the button to serialize the values in the <form> block, but I don't know quite how to do that. Go ahead and take a look at my javascript code (index.js) and slay me, or, I mean, my code. It's still pretty elementary and short (~260 lines, that's short right?). I will take any help for this problem (as the matter of fact, if you see any other problems or a better way of implementation of something, go ahead and mention that too); tips, advice, code samples, or whatever else you can contribute, it will be greatly appreciated. Tri

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• TimeoutException when WCF Host and Client are in the same process

  - by Pharao2k

  I've ran into a really weird problem. I am building a heavily distributed application where each app instance can either be a Host and/or Client to a WCF-Service (very p2p-like). Everything works fine, as long as the Client and the targeted Host (By which I mean the app, not the Host, since currently everything runs on a single computer (so no Firewall problems etc.)) are NOT the same. IF they are the same, then the app hangs for exactly 1 Minute and then throws a TimeoutException. WCF-Logging did not produce anything helpful. Here is a small app which demonstrates the Problem: public partial class MainWindow : Window { public MainWindow() { InitializeComponent(); } private void button1_Click(object sender, RoutedEventArgs e) { var binding = new NetTcpBinding(); var baseAddress = new Uri(@"net.tcp://localhost:4000/Test"); ServiceHost host = new ServiceHost(typeof(TestService), baseAddress); host.AddServiceEndpoint(typeof(ITestService), binding, baseAddress); var debug = host.Description.Behaviors.Find<ServiceDebugBehavior>(); if (debug == null) host.Description.Behaviors.Add(new ServiceDebugBehavior { IncludeExceptionDetailInFaults = true }); else debug.IncludeExceptionDetailInFaults = true; host.Open(); var clientBinding = new NetTcpBinding(); var testProxy = new TestProxy(clientBinding, new EndpointAddress(baseAddress)); testProxy.Test(); } } [ServiceContract] public interface ITestService { [OperationContract] void Test(); } public class TestService : ITestService { public void Test() { MessageBox.Show("foo"); } } public class TestProxy : ClientBase<ITestService>, ITestService { public TestProxy(NetTcpBinding binding, EndpointAddress remoteAddress) : base(binding, remoteAddress) { } public void Test() { Channel.Test(); } } What am I doing wrong? Regards, Pharao2k

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• How to write a custom solution using a python package, modules etc

  - by morpheous

  I am writing a packacge foobar which consists of the modules alice, bob, charles and david. From my understanding of Python packages and modules, this means I will create a folder foobar, with the following subdirectories and files (please correct if I am wrong) foobar/ __init__.py alice/alice.py bob/bob.py charles/charles.py david/david.py The package should be executable, so that in addition to making the modules alice, bob etc available as 'libraries', I should also be able to use foobar in a script like this: python foobar --args=someargs Question1: Can a package be made executable and used in a script like I described above? Question 2 The various modules will use code that I want to refactor into a common library. Does that mean creating a new sub directory 'foobar/common' and placing common.py in that folder? Question 3 How will the modules foo import the common module ? Is it 'from foobar import common' or can I not use this since these modules are part of the package? Question 4 I want to add logic for when the foobar package is being used in a script (assuming this can be done - I have only seen it done for modules) The code used is something like: if __name__ == "__main__": dosomething() where (in which file) would I put this logic ?

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• C# Delegate under the hood question.

  - by Ted

  Hi Guys I was doing some digging around into delegate variance after reading the following tquestion in SO. "delegate-createdelegate-and-generics-error-binding-to-target-method" (sorry not allowed to post more than one hyperlink as a newbie here!) I found a very nice bit of code from Barry kelly at https://www.blogger.com/comment.g?blogID=8184237816669520763&postID=2109708553230166434 Here it is (in a sugared-up form :-) using System; namespace ConsoleApplication4 { internal class Base { } internal class Derived : Base { } internal delegate void baseClassDelegate(Base b); internal delegate void derivedClassDelegate(Derived d); internal class App { private static void Foo1(Base b) { Console.WriteLine("Foo 1"); } private static void Foo2(Derived b) { Console.WriteLine("Foo 2"); } private static T CastDelegate<T>(Delegate src) where T : class { return (T) (object) Delegate.CreateDelegate( typeof (T), src.Target, src.Method, true); // throw on fail } private static void Main() { baseClassDelegate a = Foo1; // works fine derivedClassDelegate b = Foo2; // works fine b = a.Invoke; // the easy way to assign delegate using variance, adds layer of indirection though b(new Derived()); b = CastDelegate<derivedClassDelegate>(a); // the hard way, avoids indirection b(new Derived()); } } } I understand all of it except this one (what looks very simple) line. b = a.Invoke; // the easy way to assign delegate using variance, adds layer of indirection though Can anyone tell me: how it is possible to call invoke without passing the param required by the static function. When is going on under the hood when you assign the return value from calling invoke What does Barry mean by extra indirection (in his comment)

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• what exactly is the danger of an uninitialized pointer in C

  - by akh2103

  I am trying get a handle on C as I work my way thru Jim Trevor's "Cyclone: A safe dialect of C" for a PL class. Trevor and his co-authors are trying to make a safe version of C, so they eliminate uninitialized pointers in their language. Googling around a bit on uninitialized pointers, it seems like un-initialized pointers point to random locations in memory. It seems like this alone makes them unsafe. If you reference an un-itilialized pointer, you jump to an unsafe part of memory. Period. But the way Trevor talks about them seems to imply that it is more complex. He cites the following code, and explains that when the function FrmGetObjectIndex dereferences f, it isn’t accessing a valid pointer, but rather an unpredictable address — whatever was on the stack when the space for f was allocated. What does Trevor mean by "whatever was on the stack when the space for f was allocated"? Are "un-initialized" pointers initialized to random locations in memory by default? Or does their "random" behavior have to do with the memory allocated for these pointers getting filled with strange values (that are then referenced) because of unexpected behavior on the stack. Form *f; switch (event->eType) { case frmOpenEvent: f = FrmGetActiveForm(); ... case ctlSelectEvent: i = FrmGetObjectIndex(f, field); ... }

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• NSOperation and fwrite (Iphone)

  - by Sridhar

  Hi, I am having problem with this code.Basically I want to execute the fwrite from a timer function asyncronusly. Here is the code block in my Timer function. (This will call by the timer every 0.2 seconds. -(void)timerFunction { WriteFileOperation * operation = [WriteFileOperation writeFileWithBuffer:pFile buffer:readblePixels length:nBytes*15]; [_queue addOperation:operation]; // Here it is waiting to complete the fwrite } The WrtiteFilerOperation is an NSoperation class which it has to write the passing buffer to a file. I added this code in WriteFileOperation's "start" method. (void)start { if (![NSThread isMainThread]) { [self performSelectorOnMainThread:@selector(start) withObject:nil waitUntilDone:NO]; return; } [self willChangeValueForKey:@"isExecuting"]; _isExecuting = YES; [self didChangeValueForKey:@"isExecuting"]; NSLog(@"write bytes %d",fwrite(_buffer, 1, _nBytes, _file)); free(_buffer); [self finish]; } The problem here is , my timerFunction blocked by NSOperation until it writes the buffer into file.(I mean blocked till start method finishes its execution) and the performance seems same as directly placing the fwrite in timerFunction. I want to just return to timerFunction with out waiting from the start method execution to be completed. What I am doing wrong here ? Thanks In Advance Raghu

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• Enumerating a string

  - by JamesB

  I have a status which is stored as a string of a set length, either in a file or a database. I'm looking to enumerate the possible status' I have the following type to define the possible status' Type TStatus = (fsNormal = Ord('N'),fsEditedOnScreen = Ord('O'), fsMissing = Ord('M'),fsEstimated = Ord('E'),fsSuspect = Ord('s'), fsSuspectFromOnScreen = Ord('o'),fsSuspectMissing = Ord('m'), fsSuspectEstimated = Ord('e')); Firstly is this really a good idea? or should I have a seperate const array storing the char conversions? That would mean more than one place to update. Now convert a string to a status array I have the following, but how can I check if a char is valid without looping through the enumeration? Function StrToStatus(Value : String):TStatusArray; var i: Integer; begin if Trim(Value) = '' then begin SetLength(Result,0); Exit; end; SetLength(Result,Length(Value)); for i := 1 to Length(Value) do begin Result[i] := TStatus(Value[i]); // I don't think this line is safe. end; end; AFAIK this should be fine for converting back again. Function StatusToStr(Value : TStatusArray):String; var i: Integer; begin for i := 0 to Length(Value) - 1 do Result := Result + Chr(Ord(Value[i])) end; I'm using Delphi 2007

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• subtotals in columns usind reshape2 in R

  - by user1043144

  I have spent some time now learning RESHAPE2 and plyr but I still do not get it. This time I have a problem with (a) subtotals and (b) passing different aggregate functions . Here an example using data from the excellent tutorial on the blog of mrdwab http://news.mrdwab.com/ # libraries library(plyr) library(reshape2) # get data and add few more variables book.sales = read.csv("http://news.mrdwab.com/data-booksales") book.sales$Stock = book.sales$Quantity + 10 book.sales$SubjCat[(book.sales$Subject == 'Economics') | (book.sales$Subject == 'Management') ] <- '1_EconSciences' book.sales$SubjCat[book.sales$Subject %in% c('Anthropology', 'Politics', 'Sociology') ] <- '2_SocSciences' book.sales$SubjCat[book.sales$Subject %in% c('Communication', 'Fiction', 'History', 'Research', 'Statistics') ] <- '3_other' # to get to my starting dataframe (close to the project I am working on) book.sales1 <- ddply(book.sales, c('Region', 'Representative', 'SubjCat', 'Subject', 'Publisher'), summarize, Stock = sum(Stock), Sold = sum(Quantity), Ratio = round((100 * sum(Quantity)/ sum(Stock)), digits = 1)) #melt it m.book.sales = melt(data = book.sales1, id.vars = c('Region', 'Representative', 'SubjCat', 'Subject', 'Publisher'), measured.vars = c('Stock', 'Sold', 'Ratio')) # cast it Tab1 <- dcast(data = m.book.sales, formula = Region + Representative ~ Publisher + variable, fun.aggregate = sum, margins = c('Region', 'Representative')) Now my questions : I have been able to add the subtotals in rows. But is it possible also to add margins in the columns. Say for example, Totals of Stock for one Publisher ? Sorry I meant to say example total sold for all publishers There is a problem with the columns with “ratio”. How can I get “mean” instead of “sum” for this variable ? P.S: I have seen some examples using reshape. Will you recommend to use it instead of reshape2 (which seems not to include the functionalities of two functions).

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• Jrails and jquery-rails together?

  - by ecoologic

  I hope you forgive me if I'm a little confused about this. Jrails rewrites all the helper methods for rjs otherwise in prototype. Jquery-rails overrides rails.js (so I taught the rjs helpers as well, but I see it's not) and the rest of the libraries in jquery instead of prototype. Does it means that with just Jquery-rails I can't use rjs at all? Then do these gems work well together and let me completely forget prototype? Is there any disadvantage in using them together? I read some complaining about the fact that jrails uses jq 1.5 and now there is 1.8, but jquery-rails gives me the last version (is there retro compatibility?), but how will this affect my development (using both the gems together)? I mean have you got some examples of jquery-ui plugins I can't use or I could have problems with? Any help is appreciated. Don't get me wrong, I'm not against prototype, just I keep on having conflicts over conflicts using both of them, and I have to chose I pick Jquery.

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• Is a confirmation screen necessary for an order form?

  - by abeger

  In a discussion about how to streamline an order form on our site, the idea of eliminating the confirmation screen. So, instead of filling out the form, clicking "Submit", seeing a summary on a confirmation screen and clicking "Confirm", the user would simply fill out the form, hit "Submit", and the order's done. The theory is that fewer clicks and fewer screens means less time to order and therefore the ordering experience is easier. The opposing opinion says that without the confirmation screen, user error increases and people just end up canceling/changing orders after the fact. I'm looking for more input from the SO community. Have you ever done this? How has it worked out, compared to a traditional confirmation screen setup? Are there examples of a true "one click and done" setup on the web (does Amazon's 1-click have a confirmation screen? I've never been courageous enough to try it)? EDIT: Just to clarify, when I say "confirmation screen", I mean a second step where the customer reviews the order before placing it. Even if we did do away with it, the user would still receive a message saying "your order has been placed".

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• Calculating bounding box a certain distance away from a lat/long coordinate in Java

  - by Bryce Thomas

  Given a coordinate (lat, long), I am trying to calculate a square bounding box that is a given distance (e.g. 50km) away from the coordinate. So as input I have lat, long and distance and as output I would like two coordinates; one being the south-west (bottom-left) corner and one being the north-east (top-right) corner. I have seen a couple of answers on here that try to address this question in Python, but I am looking for a Java implementation in particular. Just to be clear, I intend on using the algorithm on Earth only and so I don't need to accommodate a variable radius. It doesn't have to be hugely accurate (+/-20% is fine) and it'll only be used to calculate bounding boxes over small distances (no more than 150km). So I'm happy to sacrifice some accuracy for an efficient algorithm. Any help is much appreciated. Edit: I should have been clearer, I really am after a square, not a circle. I understand that the distance between the center of a square and various points along the square's perimeter is not a constant value like it is with a circle. I guess what I mean is a square where if you draw a line from the center to any one of the four points on the perimeter that results in a line perpendicular to a side of the perimeter, then those 4 lines have the same length.

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• Does this mimic perfectly a function template specialization?

  - by zeroes00

  Since the function template in the following code is a member of a class template, it can't be specialized without specializing the enclosing class. But if the compiler's full optimizations are on (assume Visual Studio 2010), will the if-else-statement in the following code get optimized out? And if it does, wouldn't it mean that for all practical purposes this IS a function template specialization without any performance cost? template<typename T> struct Holder { T data; template<int Number> void saveReciprocalOf(); }; template<typename T> template<int Number> void Holder<T>::saveReciprocalOf() { //Will this if-else-statement get completely optimized out if(Number == 0) data = (T)0; else data = (T)1 / Number; } //----------------------------------- void main() { Holder<float> holder; holder.saveReciprocalOf<2>(); cout << holder.data << endl; }

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• Code bacteria: evolving mathematical behavior

  - by Stefano Borini

  It would not be my intention to put a link on my blog, but I don't have any other method to clarify what I really mean. The article is quite long, and it's in three parts (1,2,3), but if you are curious, it's worth the reading. A long time ago (5 years, at least) I programmed a python program which generated "mathematical bacteria". These bacteria are python objects with a simple opcode-based genetic code. You can feed them with a number and they return a number, according to the execution of their code. I generate their genetic codes at random, and apply an environmental selection to those objects producing a result similar to a predefined expected value. Then I let them duplicate, introduce mutations, and evolve them. The result is quite interesting, as their genetic code basically learns how to solve simple equations, even for values different for the training dataset. Now, this thing is just a toy. I had time to waste and I wanted to satisfy my curiosity. however, I assume that something, in terms of research, has been made... I am reinventing the wheel here, I hope. Are you aware of more serious attempts at creating in-silico bacteria like the one I programmed? Please note that this is not really "genetic algorithms". Genetic algorithms is when you use evolution/selection to improve a vector of parameters against a given scoring function. This is kind of different. I optimize the code, not the parameters, against a given scoring function.

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• nhibernate - mapping with contraints

  - by Tobias Müller

  Hello everybody, I am having a Problem with my nhibernate-mapping and I can't find a solution by searching on stackoverflow/google/documentation. The database I am using has (amongst others) two tables. One is unit with the following fields: id enduring_id starts ends damage_enduring_id [...] The other one is damage, which has the following fields: id enduring_id starts ends [...] The units are assigned to a damage and one damage can have zero, one or more units working on it. Every time a unit moves to annother damage, the dataset is copied. The field "ends" of the old record and "starts" of the new record are set to the current time stamp, enduring_id stays the same. So if I want to know which units were working on a damage at a certain time, I do the following select: select * from unit join damage on damage.enduring_id = unit.damage_enduring_id where unit.starts <= 'time' and unit.ends = 'time' (This is not an actualy query from the database, I made it up to make clear what I mean. The the real database is a little more complex) Now I want to map it that way, so I can load all the damages which are valid at one time (starts <= wanted time <= ends) and that each of them has a Bag with all the attached units at that time (again starts <= wanted time <= ends). Is this possible within the mapping? Sorry if this is a stupid question, but I am pretty new to nhibernate and I have no clue how to do it. Thanks a lot for reading my post! Bye, Tobias

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• WPF XAML references not resolved via myAssembly.GetReferencedAssemblies()

  - by WPF-it

  I have a WPF container application (with ContentControl host) and a containee application (UserControl). Both are oblivious of each other. Only one XML config file holds the string dllpath of the containee's DLL and full namespace name of the ViewModelClass inside the containee. A generic code in container resolves containee's assembly (Assembly.LoadFrom(dllpath)) and creates the viewmodel's instance using Activator.CreateInstance(vmType). when this viewmodel is hosted inside the ContentControl of the container, and relevant vierwmodel specific ResourceDictionary is added to ContentControl.Resources.MergedDictionaries of the content control of container, so the view loads fine. Now my containee has to host the WPF DataGrid using assembly reference of WPFToolkit.dll from my local C:\Lib folder. The Copy Local reference to the WPFToolkit.dll is added to the .csproj file of the containee's project and its only referred in the UserControl.XAML using its XAML namepsace. This way my bin\debug folder in my containee application, gets the WPFToolkit.dll copied. XAML: xmlns:Controls="clr-namespace:Microsoft.Windows.Controls;assembly=WPFToolkit" <Controls:DataGrid ItemsSource="{Binding AssetList}" ... /> Issue: The moment the ViewModel (i.e. the containee's usercontrol) tries to load itself I get this error. "Cannot find type 'Microsoft.Windows.Controls.DataGrid'. The assembly used when compiling might be different than that used when loading and the type is missing." Hence I tried to load the referenced assemblies of the containee's assembly (myAssembly.GetReferencedAssemblies()) before the viewmodel is hosted. But WPFToolkit isnt there in that list of assemblies! Strange thing is I have another dll referred called Logger.dll in the containee codebase but this one is implemented using C# code behind. So I get its reference correctly resolved in myAssembly.GetReferencedAssemblies(). So does that mean BAML references of assemblies are never resolvable by GetReferencedAssemblies?

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