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  • When to use pointer to a class and when to just instantiate it as a variable

    - by Enders
    Im sort of confused by it. The best I could find was reading through the cplusplus.com tutorial and all they have to say about pointers to classes. "It is perfectly valid to create pointers that point to classes. We simply have to consider that once declared, a class becomes a valid type, so we can use the class name as the type for the pointer" Which tells me nothing about when to use them over the normal instantiation. I've seen the - operator many times, and looked at some codes but cant really decipher why they did it. Generic examples will be appreciated; but more specifically related to gui programming. Its where I encountered it first. QGridLayout *mainLayout = new QGridLayout; mainLayout->addWidget(nameLabel, 0, 0); mainLayout->addWidget(nameLine, 0, 1); mainLayout->addWidget(addressLabel, 1, 0, Qt::AlignTop); mainLayout->addWidget(addressText, 1, 1); Why not QGridLayout mainLayout mainLayout.addWidget ... (It doesnt compile if I change the sample code to that and try it but you get the point) Thanks in advance

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  • Has inheritance become bad?

    - by mafutrct
    Personally, I think inheritance is a great tool, that, when applied reasonably, can greatly simplify code. However, I seems to me that many modern tools dislike inheritance. Let's take a simple example: Serialize a class to XML. As soon as inheritance is involved, this can easily turn into a mess. Especially if you're trying to serialize a derived class using the base class serializer. Sure, we can work around that. Something like a KnownType attribute and stuff. Besides being an itch in your code that you have to remember to update every time you add a derived class, that fails, too, if you receive a class from outside your scope that was not known at compile time. (Okay, in some cases you can still work around that, for instance using the NetDataContract serializer in .NET. Surely a certain advancement.) In any case, the basic principle still exists: Serialization and inheritance don't mix well. Considering the huge list of programming strategies that became possible and even common in the past decade, I feel tempted to say that inheritance should be avoided in areas that relate to serialization (in particular remoting and databases). Does that make sense? Or am messing things up? How do you handle inheritance and serialization?

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  • Error compiling basic java code

    - by Michael Younani
    New to java. Practicing coding by following a book. Heres my code: class Motorcycle { //Three instance variables - make and color are strings. while a boolean refers to TRUE OR FLASE(in this case off or on) String make; String color; boolean engineState; void startEngine() { if (engineState == true) System.out.print("The engine is already on."); else { engineState = true; System.out.print("The engine is now on."); } void showAtts() { System.out.print("This motorcycle is a " + color + " " + make); if (engineState ==true) System.out.print("The engine is on."); else System.out.print("The engine is off."); } } } When I compile I get 2 errors: 1) illegal start of expression 2) ; expected I can't pin point the problem. If anyone can direct me or hint me please do.

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  • How to construct objects based on XML code?

    - by the_drow
    I have XML files that are representation of a portion of HTML code. Those XML files also have widget declarations. Example XML file: <message id="msg"> <p> <Widget name="foo" type="SomeComplexWidget" attribute="value"> inner text here, sets another attribute or inserts another widget to the tree if needed... </Widget> </p> </message> I have a main Widget class that all of my widgets inherit from. The question is how would I create it? Here are my options: Create a compile time tool that will parse the XML file and create the necessary code to bind the widgets to the needed objects. Advantages: No extra run-time overhead induced to the system. It's easy to bind setters. Disadvantages: Adds another step to the build chain. Hard to maintain as every widget in the system should be added to the parser. Use of macros to bind the widgets. Complex code Find a method to register all widgets into a factory automatically. Advantages: All of the binding is done completely automatically. Easier to maintain then option 1 as every new widget will only need to call a WidgetFactory method that registers it. Disadvantages: No idea how to bind setters without introducing a maintainability nightmare. Adds memory and run-time overhead. Complex code What do you think is better? Can you guys suggest a better solution?

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  • trouble with state monad composition

    - by user1308560
    I was trying out the example given at http://www.haskell.org/haskellwiki/State_Monad#Complete_and_Concrete_Example_1 How this makes the solution composible is beyond my understanding. Here is what I tried but I get compile errors as follows: Couldn't match expected type `GameValue -> StateT GameState Data.Functor.Identity.Identity b0' with actual type `State GameState GameValue' In the second argument of `(>>=)', namely `g2' In the expression: g1 >>= g2 In an equation for `g3': g3 = g1 >>= g2 Failed, modules loaded: none. Here is the code: See the end lines module StateGame where import Control.Monad.State type GameValue = Int type GameState = (Bool, Int) -- suppose I want to play one game after the other g1 = playGame "abcaaacbbcabbab" g2 = playGame "abcaaacbbcabb" g3 = g1 >>= g2 m2 = print $ evalState g3 startState playGame :: String -> State GameState GameValue playGame [] = do (_, score) <- get return score playGame (x:xs) = do (on, score) <- get case x of 'a' | on -> put (on, score + 1) 'b' | on -> put (on, score - 1) 'c' -> put (not on, score) _ -> put (on, score) playGame xs startState = (False, 0) main str = print $ evalState (playGame str) startState

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  • Can't declare an abstract method private....

    - by Zombies
    I want to do this, yet I can't. Here is my scenario and rational. I have an abstract class for test cases that has an abstract method called test(). The test() method is to be defined by the subclass; it is to be implemented with logic for a certain application, such as CRMAppTestCase extends CompanyTestCase. I don't want the test() method to be invoked directly, I want the super class to call the test() method while the sub class can call a method which calls this (and does other work too, such as setting a current date-time right before the test is executed for example). Example code: public abstract class CompanyTestCase { //I wish this would compile, but it cannot be declared private private abstract void test(); public TestCaseResult performTest() { //do some work which must be done and should be invoked whenever //this method is called (it would be improper to expect the caller // to perform initialization) TestCaseResult result = new TestCaseResult(); result.setBeginTime(new Date()); long time = System.currentTimeMillis(); test(); //invoke test logic result.setDuration(System.currentTimeMillis() - time); return result; } } Then to extend this.... public class CRMAppTestCase extends CompanyTestCase { public void test() { //test logic here } } Then to call it.... TestCaseResult result = new CRMAppTestCase().performTest();

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  • Can't Add XSD to Class Project

    - by Jeff
    Background: I started with a large solution with many applications in it in VS 2008 and I'm trying to split it up. Steps to repeat: I create a new VS 2010 C# class project I right click and choose add existing item I choose the XSD file from my old project and import it. The original file is 67KB the imported file is 18KB Line 134,135 of the original file <Mapping SourceColumn="ConfigType" DataSetColumn="ConfigType" /> <Mapping SourceColumn="ConfigValue" DataSetColumn="ConfigValue" /> Line 135,136 of the resulting file <Mapping SourceColumn="ConfigType" DataSetColumn="ConfigType" /> <Mappi Part way through it's life my old project was upgrade from 2.0 to 3.5 so some of the code is. Manually copy and paste of the xsd source into the new file and updating the 2.0.0.0 to 4.0.0.0 allowed me to open it it in The GUI for editing XSD files. After fixing all the connection strings and right clicking on every query and clicking configure then finish I was able to gain access to one of the tableadapters out of 6. I'm stumped as to hoe to get this to compile. Once it compiles I'm open sourcing it so ask if you want to see the code.

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  • Python script not working when run from browser directly

    - by splatterdash
    I'm trying to run this script: import re, os def build_pool(cwd): global xtn_pool, file_pool xtn, xtn_pool = re.compile('\\.[0-9a-zA-Z]{1,4}$'), [] file_pool = [files for files in os.listdir(cwd) if os.path.isfile(files) and xtn.search(files)] # Lists all the file extension in the folder for file in file_pool: if not xtn_pool.__contains__(xtn.search(file).group()): xtn_pool.append(xtn.search(file).group()) return xtn_pool.sort(), file_pool if __name__ == '__main__': import sys #if path is given, change working directory to path if len(sys.argv) >= 2: os.chdir(sys.argv[1]) build_pool(os.getcwd()) #if no path is given when running, do renaming in current folder else: build_pool(os.getcwd()) print('The folder contains the following extensions: ') for i in range(0, len(xtn_pool)): print(repr(i+1) + '. ' + xtn_pool[i][1:]) opt = int(input('Which one would you like to replace? ')) xtn_pick = xtn_pool[opt-1] # Lists all the file with the chosen extension xtn_file_pool = [file for file in file_pool if file.endswith(xtn_pick)] print('There are {0} files with the {1} extension.'.format(len(xtn_file_pool), xtn_pick)) xtn_new = input('Input replacement extension: ') # The actual renaming process for file in xtn_file_pool: os.rename(file, file[:-len(xtn_pick)+1] + xtn_new) directly from my file browser (Nautilus), but for some reason it's not working. When I run it from terminal (python3 scriptname.py) it works fine as intended. But when I just click the script file in Nautilus, choose 'Run in Terminal', it always stops after asking 'Input replacement extension: '. How can I make this script run without using the terminal?

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  • Generic Singleton Fasade design pattern

    - by Paul
    Hi I try write singleton fasede pattern with generics. I have one problem, how can I call method from generic variable. Something like this: T1 t1 = new T1(); //call method from t1 t1.Method(); In method SingletonFasadeMethod I have compile error: Error 1 'T1' does not contain a definition for 'Method' and no extension method 'Method' accepting a first argument of type 'T1' could be found (are you missing a using directive or an assembly reference?) Any advace? Thank, I am beginner in C#. All code is here: namespace GenericSingletonFasade { public interface IMyInterface { string Method(); } internal class ClassA : IMyInterface { public string Method() { return " Calling MethodA "; } } internal class ClassB : IMyInterface { public string Method() { return " Calling MethodB "; } } internal class ClassC : IMyInterface { public string Method() { return "Calling MethodC"; } } internal class ClassD : IMyInterface { public string Method() { return "Calling MethodD"; } } public class SingletonFasade<T1,T2,T3> where T1 : class,new() where T2 : class,new() where T3 : class,new() { private static T1 t1; private static T2 t2; private static T3 t3; private SingletonFasade() { t1 = new T1(); t2 = new T2(); t3 = new T3(); } class SingletonCreator { static SingletonCreator() { } internal static readonly SingletonFasade<T1,T2,T3> uniqueInstace = new SingletonFasade<T1,T2,T3>(); } public static SingletonFasade<T1,T2,T3> UniqueInstace { get { return SingletonCreator.uniqueInstace; } } public string SingletonFasadeMethod() { //Problem is here return t1.Method() + t2.Method() + t3.Method(); } } }

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  • Tools for Automated Source Code Editing

    - by Steve
    I'm working on a research project to automatically modify code to include advanced mathematical concepts (like adding random effects into a loop or encapsulating an existing function with a new function that adds in a more advanced physical model). My question to the community is: are there are any good tools for manipulating source code directly? I want to do things like Swap out functions Add variable declarations wherever they are required Determine if a function is multiplied by anything Determine what functions are called on a line of code See what parameters are passed to a function and replace them with alternatives Introduce new function calls on certain lines of code Wherever possible just leaving the rest of the code untouched and write out the results I never want to actually compile the code I only want to understand what symbols are used, replace and add in a syntactically correct way, and be able to declare variables at the right position. I've been using a minimal flex/bison approach with some success but I do not feel the it is robust. I hate to take on writing a full language parser just to add some new info to the end of a line or the top of a function. It seems like this is almost what is going to be required but it also seems like there should be some tools out there to do these types of manipulations already. The code to be changed is in a variety of languages, but I'm particularly interested in FORTRAN. Any thoughts?

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  • VB - Any way to put 'Resources' items in a Resources subfolder?

    - by NotQuiteThereYet
    I have a VB.NET 2010 project that contains a lot of resources (which I added via My Project -- Resources). And they work just fine. But what I would like to do (if possible) is organize them by putting them in various subfolders. For example... in the Solution Explorer, I right-click on the 'Resources' folder and choose 'Add new folder' (which adds a subfolder inside the Resources folder). But when I try to drag one of the Resources items into the subfolder, it doesn't work (it throws an error message stating "Resource could not be loaded because the file to which it is linked could not be found"). So... I was wondering if there is any workaround for this? Since I have so many resources in this project, it would really be helpful if I could have about a dozen subfolders INSIDE the Resources folder, and then put my resources items inside those subfolders. FYI... this is strictly for my own organizational needs while coding the project, so I could care less how the resources items and folders are arranged at compile time. Thanks!

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  • Using pair in c++

    - by user1543957
    Can someone please tell why i am unable to compile the following program #include<iostream> #include<string> #include<cmath> #include<iostream> #include<cfloat> #define MOD 10000009 using namespace std; double distance(pair<int,int> p1,pair<int,int> p2) { double dist; dist = sqrt( (p1.first-p2.first)*(p1.first-p2.first) + (p1.second-p2.second)*(p1.second-p2.second) ); return(dist); } int main() { int N,i,j; cin >> N; pair<int,int> pi[N]; for(i=0;i<N;i++) { cin >> pi[i].first >> pi[i].second; } for(i=0;i<N;i++) { cout << pi[i].first << " "<< pi[i].second << endl; } distance(pi[0],pi[1]); // This line is giving error return 0; }

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  • Google App Engine/GWT/Eclipse Plugin Newbie Question- how to autobuild client side resources?

    - by Dieter Hanover
    Hi there, I'm tinkering with the default GWT application generated by the Google Eclipse plugin when I click the Google "New Web Application Project" button in Eclipse 3.5. This will no doubt be familiar to many of you.. basically there is an h1 title stating "Web Application Starter Project," a text field, and a Send button. What I've found is that whenever I make changes to the client side resources, e.g. change the text on the Send button to "Submit" in the .java file, Eclipse does not appear to autobuild these resources. In fact I have to rebuild the entire project in order for these changes to be reflected in my browser. I do have "build automatically" selected in eclipse. I should state that this is my second GWT project, the first was almost entirely server side (restlet on GAE) and everything built automatically nicely. When I first tried this new project with updated client resources, on refreshing my browser, the browser stated "you may need to (re)compile your project." I'm not sure if this is relevant but I thought I'd mention it all the same. So what's going on? How do I get Eclipse/GWT to autobuild these client side resources? Cheers for any help you can offer! :-)

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  • StackOverflow Error at java.util.AbstractColllection.<init>(Unknown Source)

    - by thebulge
    I fixed my prior problem yesterday by just separating all the classes into separate files. Nevertheless, I wrote all the code down and seeing no errors was able to compile the program. Or so I thought. Here's the error code: Exception in thread "main" java.lang.StackOverflowError at java.util.AbstractCollection.<init>(Unknown Source) at java.util.AbstractList.<init>(Unknown Source) at java.util.Vector.<init>(Unknown Source) at java.util.Vector.<init>(Unknown Source) at java.util.Vector.<init>(Unknown Source Here are the spots where my I get the errors(marked with problem?) public class GameWorld implements IObservable, IGameWorld { // create collections class public Vector<GameObject> GameObjectList = new Vector<GameObject>(); // PROBLEM private Vector<IObserver> ObserverList = new Vector<IObserver>(); // declare objects Tank pTank = new Tank(10, 10); // other objects and variables to declare public GameWorld() { // add objects to GameObjectList } // accessors/mutators } I get another error here public class Tank extends Movable implements ISteerable { private int armorStrength; private int missileCount; public Tank() {} public Tank(int armStr, int misslCt) // problem? { armorStrength = armStr; // default armorStrength missileCount = misslCt; // default missileCount } public void setDirection(int direction) { this.setDirection(direction); // get input from left turn or right turn // updateValues(); } // access/mutators here I'm stumped on what to do here.

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  • What is the most obfuscated and clever code you've seen? [closed]

    - by ThibThib
    I am aware about the The International Obfuscated C Code Contest, but I am looking for obfuscated AND clever codes (specially short ones) Here is two examples (the first one is a classical one, I think) #define _ F-->00 || F-OO--; long F=00,OO=00; main(){F_OO();printf("%1.3f\n", 4.*-F/OO/OO);}F_OO() { _-_-_-_ _-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_ _-_-_-_ } and #include <unistd.h> float o=0.075,h=1.5,T,r,O,l,I;int _,L=80,s=3200;main(){for(;s%L|| (h-=o,T= -2),s;4 -(r=O*O)<(l=I*I)|++ _==L&&write(1,(--s%L?_<L?--_ %6:6:7)+"World! \n",1)&&(O=I=l=_=r=0,T+=o /2))O=I*2*O+h,I=l+T-r;} I let you compile and run them so as to understand what they are producing. Of course, I am not looking for only obfuscated code, because I guess that every code could be transformed in a way that it is not readable at all I am more looking for small codes that you can eventually understand, with some clever tricks. I will show them to my students as example of clever things that they should not do (it's always better to show clever examples rather than stupid ones...) Thanks

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  • Code producing System.NullReferenceException error for Membership.GetUser(). This is VB.Net (ASP.Net 4)

    - by Derrek
    I have a Default.aspx page that is not static. I have added functionality with datalist and sqldatasources. When a user logins he/she will see items like saved workouts, saved equipment, total replys, etc... This is based on getting the currently logged in user UserID. Quite simply this works great when the user is logged in. However, I do not want to force a user to login to view the Default page because it does have functionality on it that does not require login. When a user is not logged in of course I receive the [System.NullReferenceException] error. I understand the error well but I do not know how to code to fix it. That is where I need help. I will admit I am more designer than developer. However, I do know the exception error I am receivving is caused by me not setting a value in my code when a user is not logged in. I do not know how to do that and have for a week made unsuccessful attempts at writing the code. Both sets of code below compile for VB.Net/ASP.Net 4/Visual Studio 2010 without errors. However, I still get the System.NullReferenceException error if not logged in. I know it can be done but I do not know the right syntax. If you can help please insert you code in mine or write it out. JUST TELLING ME WHERE TO GO TO FIND AN ANSWER WON'T HELP. I HAVE DONE THAT FOR 7 STRAIGHT DAYS. I APPRECIATE OUR HELP. Partial Class _Default Inherits System.Web.UI.Page Protected Sub SqlDataSource4_Selecting(ByVal sender As Object, ByVal e As SqlDataSourceCommandEventArgs) Handles SqlDataSource4.Selecting Dim MemUser As MembershipUser MemUser = Membership.GetUser() If Not MemUser Is DBNull.Value Then UserID.Text = MemUser.ProviderUserKey.ToString() e.Command.Parameters("@UserId").Value = MemUser.ProviderUserKey.ToString() End If End Sub -------------------------------------ORIGINAL CODE------------------------------- Partial Class _Default Inherits System.Web.UI.Page Protected Sub SqlDataSource4_Selecting(ByVal sender As Object, ByVal e As SqlDataSourceCommandEventArgs) Handles SqlDataSource4.Selecting Dim MemUser As MembershipUser MemUser = Membership.GetUser() UserID.Text = MemUser.ProviderUserKey.ToString() e.Command.Parameters("@UserId").Value = MemUser.ProviderUserKey.ToString() End Sub

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  • C++ Template Iterator error

    - by gprime
    I am going over some code i wrote in 2006 as an undergrad. It's a simple genetic algorithm library written in C++ using templates. It use to work in 2006 when i coded it with visual studio, but now when i am trying to run it in xcode i get compile errors. This function is giving me errors: friend bool operator==(const TSPGenome<T> & t1, const TSPGenome<T> & t2) { // loop through each interator and check to see if the two genomes have the same values if(t1.genome_vec->size() != t2.genome_vec->size()) return false; else { // iterate through each vector<T>::iterator it_t1; vector<T>::iterator it_t2; it_t1 = t1.genome_vec->begin(); for(it_t2 = t2.genome_vec->begin(); it_t2 != t2.genome_vec->end(); ++it_t2, ++it_t1) { if(*it_t2 != *it_t1) return false; } } // everything seems good return true; } xcode complains about these two lines not having ; before it_t1 and it_t2. vector<T>::iterator it_t1; vector<T>::iterator it_t2; Is it because the vector type it T? I declared it in the class as follows: template <typename T> class TSPGenome : public Genome { Any help would be appreciated. Thanks!

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  • OcaIDE doesn't see JoCaml tools

    - by Surikator
    I'm having a problem while using OcaIDE in ocamlbuild mode. I'm trying to compile my own JoCaml sources. According to the JoCaml manual (bottom of page), to use ocamlbuild with JoCaml, I just need to add the -use-jocaml argument to ocamlbuild. Indeed, if I go to the root of my project and write ocamlbuild -use-jocaml foo.native it generates my executable just fine. However, in OcaIDE I get /bin/sh: jocamldep: command not found In OcaIDE, the -use-jocaml flag is passed in the "Other Flags" box (in Project Properties). And that certainly is working, as the complaint is precisely that it doesn't find jocaml stuff. The puzzling thing is that jocaml is installed and can be accessed from any random terminal window. For example, running jocamldep -modules foo.ml > foo.ml.depends on my project does generate the desired dependency file. So, it would seem I would have to configure OcaIDE and tell it where JoCaml executables are or something. This is done for OCaml, for example. But there is no place to do that for JoCaml. And it's really strange that, if jocamldep/jocamlc/etc are all accessible from anywhere, OcaIDE wouldn't be able to pick them. Any ideas? (I am aware I can do an ocamlbuild plugin and pass the flag in a "myocamlbuild.ml" file. I'll probably use that a latter stage after I get familiar with ocamlbuild plugins. But here the question is about OcaIDE. EDIT: Actually, ocamlbuild plugins don't seem to be a solution as, although there is an option -use-jocaml in ocamlbuild to enforce jocaml use (and it works fine), the plugin system doesn't support it, i.e. jocaml is not in the list of options.)

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  • Strange type-related error

    - by vsb
    I wrote following program: isPrime x = and [x `mod` i /= 0 | i <- [2 .. truncate (sqrt x)]] primes = filter isPrime [1 .. ] it should construct list of prime numbers. But I got this error: [1 of 1] Compiling Main ( 7/main.hs, interpreted ) 7/main.hs:3:16: Ambiguous type variable `a' in the constraints: `Floating a' arising from a use of `isPrime' at 7/main.hs:3:16-22 `RealFrac a' arising from a use of `isPrime' at 7/main.hs:3:16-22 `Integral a' arising from a use of `isPrime' at 7/main.hs:3:16-22 Possible cause: the monomorphism restriction applied to the following: primes :: [a] (bound at 7/main.hs:3:0) Probable fix: give these definition(s) an explicit type signature or use -XNoMonomorphismRestriction Failed, modules loaded: none. If I specify signature for isPrime function explicitly: isPrime :: Integer -> Bool isPrime x = and [x `mod` i /= 0 | i <- [2 .. truncate (sqrt x)]] I can't even compile isPrime function: [1 of 1] Compiling Main ( 7/main.hs, interpreted ) 7/main.hs:2:45: No instance for (RealFrac Integer) arising from a use of `truncate' at 7/main.hs:2:45-61 Possible fix: add an instance declaration for (RealFrac Integer) In the expression: truncate (sqrt x) In the expression: [2 .. truncate (sqrt x)] In a stmt of a list comprehension: i <- [2 .. truncate (sqrt x)] 7/main.hs:2:55: No instance for (Floating Integer) arising from a use of `sqrt' at 7/main.hs:2:55-60 Possible fix: add an instance declaration for (Floating Integer) In the first argument of `truncate', namely `(sqrt x)' In the expression: truncate (sqrt x) In the expression: [2 .. truncate (sqrt x)] Failed, modules loaded: none. Can you help me understand, why am I getting these errors?

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  • Using the JPA Criteria API, can you do a fetch join that results in only one join?

    - by Shaun
    Using JPA 2.0. It seems that by default (no explicit fetch), @OneToOne(fetch = FetchType.EAGER) fields are fetched in 1 + N queries, where N is the number of results containing an Entity that defines the relationship to a distinct related entity. Using the Criteria API, I might try to avoid that as follows: CriteriaBuilder builder = entityManager.getCriteriaBuilder(); CriteriaQuery<MyEntity> query = builder.createQuery(MyEntity.class); Root<MyEntity> root = query.from(MyEntity.class); Join<MyEntity, RelatedEntity> join = root.join("relatedEntity"); root.fetch("relatedEntity"); query.select(root).where(builder.equals(join.get("id"), 3)); The above should ideally be equivalent to the following: SELECT m FROM MyEntity m JOIN FETCH myEntity.relatedEntity r WHERE r.id = 3 However, the criteria query results in the root table needlessly being joined to the related entity table twice; once for the fetch, and once for the where predicate. The resulting SQL looks something like this: SELECT myentity.id, myentity.attribute, relatedentity2.id, relatedentity2.attribute FROM my_entity myentity INNER JOIN related_entity relatedentity1 ON myentity.related_id = relatedentity1.id INNER JOIN related_entity relatedentity2 ON myentity.related_id = relatedentity2.id WHERE relatedentity1.id = 3 Alas, if I only do the fetch, then I don't have an expression to use in the where clause. Am I missing something, or is this a limitation of the Criteria API? If it's the latter, is this being remedied in JPA 2.1 or are there any vendor-specific enhancements? Otherwise, it seems better to just give up compile-time type checking (I realize my example doesn't use the metamodel) and use dynamic JPQL TypedQueries.

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  • Output error in comparing characters from two strings

    - by Andrew Martin
    I'm stuck with my a piece of code I'm creating. My IDE is Eclipse and when I use its debugging feature, to trace what's happening on each line, it outputs perfectly. However, when I click the "run" project, it just outputs a blank screen: public static void compareInterests(Client[] clientDetails) { int interests = 0; for (int p = 0; p < numberOfClients; p++) { for (int q = 0; q < numberOfClients; q++) { String a = clientDetails[p].getClientInterests(); String b = clientDetails[q].getClientInterests(); int count = 0; while (count < a.length()) { if (a.charAt(count) == b.charAt(count)) interests++; count++; } if ((interests >= 3) && (clientDetails[p].getClientName() != clientDetails[q].getClientName())) System.out.print (clientDetails[p].getClientName() + " is compatible with " + clientDetails[q].getClientName()); interests = 0; } } } The code is designed to import an object array which contains information on a client's name and a client's interests. The client's interests are stored in the format "01010", where each 1 means they are interested in that activity, each 0 means they are not. My code compares each character of every client's string with every other client's string and outputs the results for all client's that don't have the same name and have three or more interests in common. When I run this code through Java's debugger, it outputs fine - but when I click run project or compile, I just get a blank screen. Any ideas?

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  • Extract information from a Func<bool, T> or alike lambda

    - by Syska
    I''m trying to build a generic cache layer. ICacheRepository Say I have the following: public class Person { public int PersonId { get; set; } public string Firstname { get; set; } public string Lastname { get; set; } public DateTime Added { get; set; } } And I have something like this: list.Where(x => x.Firstname == "Syska"); Here I want to extract the above information, to see if the query supplied the "PersonId" which it did not, so I dont want to cache it. But lets say I run a query like this: list.Where(x => x.PersonId == 10); Since PersonId is my key ... I want to cache it. with the key like "Person_10" and I later can fetch it from the cache. I know its possible to extract the information with Expression<Func<>> but there seems to be a big overhead of doing this (when running compile and extract the Constant values etc. and a bunch of cache to be sure to parse right) Are there a framework for this? Or some smart/golden way of doing this ?

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  • Exclude notes based on attribute wildcard in XSL node selection

    - by C A
    Using cruisecontrol for continuous integration, I have some annoyances with Weblogic Ant tasks and how they think that server debug information are warnings rather than debug, so are shown in my build report emails. The XML output from cruise is similar to: <cruisecontrol> <build> <target name="compile-xxx"> <task name="xxx" /> </target> <target name="xxx.weblogic"> <task name="wldeploy"> <message priority="warn">Message which isn't really a warning"</message> </task> </target> </build> </cruisecontrol> In the cruisecontrol XSL template the current selection for the task list is: <xsl:variable name="tasklist" select="/cruisecontrol/build//target/task"/> What I would like is something which selects the tasklist in the same way, but doesn't include any target nodes which have the attribute name="*weblogic" where * is a wildcard. I have tried <xsl:variable name="tasklist" select="/cruisecontrol/build//target[@name!='*weblogic']/task"/> but this doesn't seem to have worked. I'm not an expert with XSLT, and just want to get this fixed so I can carry on the real development of the project. Any help is much appreciated.

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  • Exclude nodes based on attribute wildcard in XSL node selection

    - by C A
    Using cruisecontrol for continuous integration, I have some annoyances with Weblogic Ant tasks and how they think that server debug information are warnings rather than debug, so are shown in my build report emails. The XML output from cruise is similar to: <cruisecontrol> <build> <target name="compile-xxx"> <task name="xxx" /> </target> <target name="xxx.weblogic"> <task name="wldeploy"> <message priority="warn">Message which isn't really a warning"</message> </task> </target> </build> </cruisecontrol> In the cruisecontrol XSL template the current selection for the task list is: <xsl:variable name="tasklist" select="/cruisecontrol/build//target/task"/> What I would like is something which selects the tasklist in the same way, but doesn't include any target nodes which have the attribute name="*weblogic" where * is a wildcard. I have tried <xsl:variable name="tasklist" select="/cruisecontrol/build//target[@name!='*weblogic']/task"/> but this doesn't seem to have worked. I'm not an expert with XSLT, and just want to get this fixed so I can carry on the real development of the project. Any help is much appreciated.

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  • Template access of symbol in unnamed namespace

    - by Fred Larson
    We are upgrading our XL C/C++ compiler from V8.0 to V10.1 and found some code that is now giving us an error, even though it compiled under V8.0. Here's a minimal example: test.h: #include <iostream> #include <string> template <class T> void f() { std::cout << TEST << std::endl; } test.cpp: #include <string> #include "test.h" namespace { std::string TEST = "test"; } int main() { f<int>(); return 0; } Under V10.1, we get the following error: "test.h", line 7.16: 1540-0274 (S) The name lookup for "TEST" did not find a declaration. "test.cpp", line 6.15: 1540-1303 (I) "std::string TEST" is not visible. "test.h", line 5.6: 1540-0700 (I) The previous message was produced while processing "f<int>()". "test.cpp", line 11.3: 1540-0700 (I) The previous message was produced while processing "main()". We found a similar difference between g++ 3.3.2 and 4.3.2. I also found in g++, if I move the #include "test.h" to be after the unnamed namespace declaration, the compile error goes away. So here's my question: what does the Standard say about this? When a template is instantiated, is that instance considered to be declared at the point where the template itself was declared, or is the standard not that clear on this point? I did some looking though the n2461.pdf draft, but didn't really come up with anything definitive.

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