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  • Odd behavior when recursively building a return type for variadic functions

    - by Dennis Zickefoose
    This is probably going to be a really simple explanation, but I'm going to give as much backstory as possible in case I'm wrong. Advanced apologies for being so verbose. I'm using gcc4.5, and I realize the c++0x support is still somewhat experimental, but I'm going to act on the assumption that there's a non-bug related reason for the behavior I'm seeing. I'm experimenting with variadic function templates. The end goal was to build a cons-list out of std::pair. It wasn't meant to be a custom type, just a string of pair objects. The function that constructs the list would have to be in some way recursive, with the ultimate return value being dependent on the result of the recursive calls. As an added twist, successive parameters are added together before being inserted into the list. So if I pass [1, 2, 3, 4, 5, 6] the end result should be {1+2, {3+4, 5+6}}. My initial attempt was fairly naive. A function, Build, with two overloads. One took two identical parameters and simply returned their sum. The other took two parameters and a parameter pack. The return value was a pair consisting of the sum of the two set parameters, and the recursive call. In retrospect, this was obviously a flawed strategy, because the function isn't declared when I try to figure out its return type, so it has no choice but to resolve to the non-recursive version. That I understand. Where I got confused was the second iteration. I decided to make those functions static members of a template class. The function calls themselves are not parameterized, but instead the entire class is. My assumption was that when the recursive function attempts to generate its return type, it would instantiate a whole new version of the structure with its own static function, and everything would work itself out. The result was: "error: no matching function for call to BuildStruct<double, double, char, char>::Go(const char&, const char&)" The offending code: static auto Go(const Type& t0, const Type& t1, const Types&... rest) -> std::pair<Type, decltype(BuildStruct<Types...>::Go(rest...))> My confusion comes from the fact that the parameters to BuildStruct should always be the same types as the arguments sent to BuildStruct::Go, but in the error code Go is missing the initial two double parameters. What am I missing here? If my initial assumption about how the static functions would be chosen was incorrect, why is it trying to call the wrong function rather than just not finding a function at all? It seems to just be mixing types willy-nilly, and I just can't come up with an explanation as to why. If I add additional parameters to the initial call, it always burrows down to that last step before failing, so presumably the recursion itself is at least partially working. This is in direct contrast to the initial attempt, which always failed to find a function call right away. Ultimately, I've gotten past the problem, with a fairly elegant solution that hardly resembles either of the first two attempts. So I know how to do what I want to do. I'm looking for an explanation for the failure I saw. Full code to follow since I'm sure my verbal description was insufficient. First some boilerplate, if you feel compelled to execute the code and see it for yourself. Then the initial attempt, which failed reasonably, then the second attempt, which did not. #include <iostream> using std::cout; using std::endl; #include <utility> template<typename T1, typename T2> std::ostream& operator <<(std::ostream& str, const std::pair<T1, T2>& p) { return str << "[" << p.first << ", " << p.second << "]"; } //Insert code here int main() { Execute(5, 6, 4.3, 2.2, 'c', 'd'); Execute(5, 6, 4.3, 2.2); Execute(5, 6); return 0; } Non-struct solution: template<typename Type> Type BuildFunction(const Type& t0, const Type& t1) { return t0 + t1; } template<typename Type, typename... Rest> auto BuildFunction(const Type& t0, const Type& t1, const Rest&... rest) -> std::pair<Type, decltype(BuildFunction(rest...))> { return std::pair<Type, decltype(BuildFunction(rest...))> (t0 + t1, BuildFunction(rest...)); } template<typename... Types> void Execute(const Types&... t) { cout << BuildFunction(t...) << endl; } Resulting errors: test.cpp: In function 'void Execute(const Types& ...) [with Types = {int, int, double, double, char, char}]': test.cpp:33:35: instantiated from here test.cpp:28:3: error: no matching function for call to 'BuildFunction(const int&, const int&, const double&, const double&, const char&, const char&)' Struct solution: template<typename... Types> struct BuildStruct; template<typename Type> struct BuildStruct<Type, Type> { static Type Go(const Type& t0, const Type& t1) { return t0 + t1; } }; template<typename Type, typename... Types> struct BuildStruct<Type, Type, Types...> { static auto Go(const Type& t0, const Type& t1, const Types&... rest) -> std::pair<Type, decltype(BuildStruct<Types...>::Go(rest...))> { return std::pair<Type, decltype(BuildStruct<Types...>::Go(rest...))> (t0 + t1, BuildStruct<Types...>::Go(rest...)); } }; template<typename... Types> void Execute(const Types&... t) { cout << BuildStruct<Types...>::Go(t...) << endl; } Resulting errors: test.cpp: In instantiation of 'BuildStruct<int, int, double, double, char, char>': test.cpp:33:3: instantiated from 'void Execute(const Types& ...) [with Types = {int, int, double, double, char, char}]' test.cpp:38:41: instantiated from here test.cpp:24:15: error: no matching function for call to 'BuildStruct<double, double, char, char>::Go(const char&, const char&)' test.cpp:24:15: note: candidate is: static std::pair<Type, decltype (BuildStruct<Types ...>::Go(BuildStruct<Type, Type, Types ...>::Go::rest ...))> BuildStruct<Type, Type, Types ...>::Go(const Type&, const Type&, const Types& ...) [with Type = double, Types = {char, char}, decltype (BuildStruct<Types ...>::Go(BuildStruct<Type, Type, Types ...>::Go::rest ...)) = char] test.cpp: In function 'void Execute(const Types& ...) [with Types = {int, int, double, double, char, char}]': test.cpp:38:41: instantiated from here test.cpp:33:3: error: 'Go' is not a member of 'BuildStruct<int, int, double, double, char, char>'

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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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  • Some clarification on rvalue references

    - by Dennis Zickefoose
    First: where are std::move and std::forward defined? I know what they do, but I can't find proof that any standard header is required to include them. In gcc44 sometimes std::move is available, and sometimes its not, so a definitive include directive would be useful. When implementing move semantics, the source is presumably left in an undefined state. Should this state necessarily be a valid state for the object? Obviously, you need to be able to call the object's destructor, and be able to assign to it by whatever means the class exposes. But should other operations be valid? I suppose what I'm asking is, if your class guarantees certain invariants, should you strive to enforce those invariants when the user has said they don't care about them anymore? Next: when you don't care about move semantics, are there any limitations that would cause a non-const reference to be preferred over an rvalue reference when dealing with function parameters? void function(T&); over void function(T&&); From a caller's perspective, being able to pass functions temporary values is occasionally useful, so it seems as though one should grant that option whenever it is feasible to do so. And rvalue references are themselves lvalues, so you can't inadvertently call a move-constructor instead of a copy-constructor, or something like that. I don't see a downside, but I'm sure there is one. Which brings me to my final question. You still can not bind temporaries to non-const references. But you can bind them to non-const rvalue references. And you can then pass along that reference as a non-const reference in another function. void function1(int& r) { r++; } void function2(int&& r) { function1(r); } int main() { function1(5); //bad function2(5); //good } Besides the fact that it doesn't do anything, is there anything wrong with that code? My gut says of course not, since changing rvalue references is kind of the whole point to their existence. And if the passed value is legitimately const, the compiler will catch it and yell at you. But by all appearances, this is a runaround of a mechanism that was presumably put in place for a reason, so I'd just like confirmation that I'm not doing anything foolish.

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  • Detect winning game in nought and crosses

    - by Dennis
    I need to know the best way to detect a winning move in a game of noughts and crosses. Source code doesn't matter, I just need a example or something I can start with. The only thing I can come up with is to use loops and test every direction for every move a player makes, to search for e.g five in a row. Is there a faster and more efficient way?

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  • Is there a way to put Setter elements inside EventTrigger?

    - by Dennis Delimarsky
    Working on a WPF application, I started working on a custom ControlTemplate. I reached the point where I need to change some control properties when an event occurs. For this purpose, there are Setter elements. Seems all good, but I cannot use them inside EventTrigger elements. For example, if a simple Trigger, that can be bound to control properties, is used then Setter elements can be used inside. However, I do not want to bind to a property change but rather to an event. Is there a way to do this in pure XAML or will I have to work in the code-behind?

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  • Calling a WCF from ASP.NET with same the single-signon user LogonUserIdentity

    - by Dennis Cheung
    I have a ASP.NET MVC page, which call WCF logic. The system is single-signon using NTML. Both the ASP page and the WCF will use the UserIdentity to get user login information. Other then NTML, I will also have a Form based authorization (with AD) in same system. The ASP page, is it simple and I can have it from HttpContext.Current.Request.LogonUserIdentity. However, it seem it is missing from the WCF which call by the ASP, not from browser. How to configure to pass the ID pass from the ASP to the WCF?

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  • Widget host app with custom view - onClick is not triggered in the app widget.

    - by Dennis K
    I'm writing an app that will host widgets. The app has custom view (which probably is the source of issue). I obtain AppWidgetHostView like this private AppWidgetHostView widget; ... AppWidgetProviderInfo appWidgetInfo = mAppWidgetManager.getAppWidgetInfo(appWidgetId); widget = mAppWidgetHost.createView(this, appWidgetId, appWidgetInfo); widget.setAppWidget(appWidgetId, appWidgetInfo); mView.addWidget(widget, appWidgetInfo); mView.addWidget() basically just remembers this AppWidgetHostView instance and then draws it directly onto canvas. Visually everything is fine - I can see the actual widget. But the issue is with reacting on UI events. Please advise what needs to be done in the parent view in order to correctly trigger handlers in the widgets like onClick(). Notes: I used standard widgets which normally react on click events. None worked. I also created my own test widget with listener (via views.setOnClickPendingIntent(R.id.appwidget_text, pending);) and onClick() is successfully triggered if the widget is added on Homescreen, but doesn't work in my app. mView correctly detects click event and I tried to call widget.performClick() there, which returns false meaning onClickListener is not registered in the widget. But according to source mAppWidgetHost.createView() would call updateAppWidget which would register its onClick listener.. Please advise where to look at. Thanks

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  • Rails: three most recent comments for unique users

    - by Dennis Collective
    class User has_many :comments end class Comment belongs_to :user named_scope :recent, :order => 'comments.created_at DESC' named_scope :limit, lambda { |limit| {:limit => limit}} named_scope :by_unique_users end what would I put in the :by_unique_users so that I can do Comment.recent.by_unique_users.limit(3), and only get one comment per user

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  • GCC error with variadic templates: "Sorry, unimplemented: cannot expand 'Identifier...' into a fixe

    - by Dennis
    While doing variadic template programming in C++0x on GCC, once in a while I get an error that says "Sorry, unimplemented: cannot expand 'Identifier...' into a fixed-length arugment list." If I remove the "..." in the code then I get a different error: "error: parameter packs not expanded with '...'". So if I have the "..." in, GCC calls that an error, and if I take the "..." out, GCC calls that an error too. The only way I have been able to deal with this is to completely rewrite the template metaprogram from scratch using a different approach, and (with luck) I eventually come up with code that doesn't cause the error. But I would really like to know what I was doing wrong. Despite Googling for it and despite much experimentation, I can't pin down what it is that I'm doing differently between variadic template code that does produce this error, and code that does not have the error. The wording of the error message seems to imply that the code should work according the C++0x standard, but that GCC doesn't support it yet. Or perhaps it is a compiler bug? Here's some code that produces the error. Note: I don't need you to write a correct implementation for me, but rather just to point out what is about my code that is causing this specific error // Used as a container for a set of types. template <typename... Types> struct TypePack { // Given a TypePack<T1, T2, T3> and T=T4, returns TypePack<T1, T2, T3, T4> template <typename T> struct Add { typedef TypePack<Types..., T> type; }; }; // Takes the set (First, Others...) and, while N > 0, adds (First) to TPack. // TPack is a TypePack containing between 0 and N-1 types. template <int N, typename TPack, typename First, typename... Others> struct TypePackFirstN { // sorry, unimplemented: cannot expand ‘Others ...’ into a fixed-length argument list typedef typename TypePackFirstN<N-1, typename TPack::template Add<First>::type, Others...>::type type; }; // The stop condition for TypePackFirstN: when N is 0, return the TypePack that has been built up. template <typename TPack, typename... Others> struct TypePackFirstN<0, TPack, Others...> //sorry, unimplemented: cannot expand ‘Others ...’ into a fixed-length argument list { typedef TPack type; }; EDIT: I've noticed that while a partial template instantiation that looks like does incur the error: template <typename... T> struct SomeStruct<1, 2, 3, T...> {}; Rewriting it as this does not produce an error: template <typename... T> struct SomeStruct<1, 2, 3, TypePack<T...>> {}; It seems that you can declare parameters to partial specializations to be variadic; i.e. this line is OK: template <typename... T> But you cannot actually use those parameter packs in the specialization, i.e. this part is not OK: SomeStruct<1, 2, 3, T... The fact that you can make it work if you wrap the pack in some other type, i.e. like this: SomeStruct<1, 2, 3, TypePack<T...>> to me implies that the declaration of the variadic parameter to a partial template specialization was successful, and you just can't use it directly. Can anyone confirm this?

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  • Counting entries in a list of dictionaries: for loop vs. list comprehension with map(itemgetter)

    - by Dennis Williamson
    In a Python program I'm writing I've compared using a for loop and increment variables versus list comprehension with map(itemgetter) and len() when counting entries in dictionaries which are in a list. It takes the same time using a each method. Am I doing something wrong or is there a better approach? Here is a greatly simplified and shortened data structure: list = [ {'key1': True, 'dontcare': False, 'ignoreme': False, 'key2': True, 'filenotfound': 'biscuits and gravy'}, {'key1': False, 'dontcare': False, 'ignoreme': False, 'key2': True, 'filenotfound': 'peaches and cream'}, {'key1': True, 'dontcare': False, 'ignoreme': False, 'key2': False, 'filenotfound': 'Abbott and Costello'}, {'key1': False, 'dontcare': False, 'ignoreme': True, 'key2': False, 'filenotfound': 'over and under'}, {'key1': True, 'dontcare': True, 'ignoreme': False, 'key2': True, 'filenotfound': 'Scotch and... well... neat, thanks'} ] Here is the for loop version: #!/usr/bin/env python # Python 2.6 # count the entries where key1 is True # keep a separate count for the subset that also have key2 True key1 = key2 = 0 for dictionary in list: if dictionary["key1"]: key1 += 1 if dictionary["key2"]: key2 += 1 print "Counts: key1: " + str(key1) + ", subset key2: " + str(key2) Output for the data above: Counts: key1: 3, subset key2: 2 Here is the other, perhaps more Pythonic, version: #!/usr/bin/env python # Python 2.6 # count the entries where key1 is True # keep a separate count for the subset that also have key2 True from operator import itemgetter KEY1 = 0 KEY2 = 1 getentries = itemgetter("key1", "key2") entries = map(getentries, list) key1 = len([x for x in entries if x[KEY1]]) key2 = len([x for x in entries if x[KEY1] and x[KEY2]]) print "Counts: key1: " + str(key1) + ", subset key2: " + str(key2) Output for the data above (same as before): Counts: key1: 3, subset key2: 2 I'm a tiny bit surprised these take the same amount of time. I wonder if there's something faster. I'm sure I'm overlooking something simple. One alternative I've considered is loading the data into a database and doing SQL queries, but the data doesn't need to persist and I'd have to profile the overhead of the data transfer, etc., and a database may not always be available. I have no control over the original form of the data. The code above is not going for style points.

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  • View Body not showing in Spring 3.2

    - by Dennis Röttger
    I'm currently trying to get into Java Web Development in general in Spring more specifically. I've set up my project as follows - hello.jsp: <html> <head> <title>Spring 3.0 MVC Series: Hello World - ViralPatel.net</title> </head> <body> <p>ABC ${message}</p> </body> </html> HelloWorldController.java: package controllers; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.servlet.ModelAndView; @Controller public class HelloWorldController { @RequestMapping("/hello") public ModelAndView helloWorld() { String message = "Hello World, Spring 3.0!"; System.out.println(message); return new ModelAndView("hello", "message", message); } } web.xml: <?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5"> <display-name>Spring3MVC</display-name> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> <servlet> <servlet-name>spring</servlet-name> <servlet-class> org.springframework.web.servlet.DispatcherServlet </servlet-class> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>spring</servlet-name> <url-pattern>*.html</url-pattern> </servlet-mapping> </web-app> spring-servlet.xml: <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd"> <context:component-scan base-package="controllers" /> <bean id="viewResolver" class="org.springframework.web.servlet.view.UrlBasedViewResolver"> <property name="viewClass" value="org.springframework.web.servlet.view.JstlView" /> <property name="prefix" value="/WEB-INF/jsp/" /> <property name="suffix" value=".jsp" /> </bean> </beans> I can start up the Server just fine and navigate to hello.html, which is resolved by the servlet to give me hello.jsp, the title of the .jsp shows (Spring 3.0 MVC Series: etc. etc.), alas, the body does not. Not the JSTL-Variable and not the "ABC" either. I've implemented jstl-1.2 in my lib-folder.

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  • How to download Google Cloud Messaging (GCM) from Google Code?

    - by Dennis
    I'm trying to learn how to use GCM and I want download the simple app. I'm following the instructions here: http://developer.android.com/google/gcm/server.html. Using App Engine for Java To set up the server using a standard App Engine for Java: Get the files from the open source site, as described above. I entered the link - https://code.google.com/p/gcm/ but there is no download there, and I don't have Git (and I don't know how to use it..). Can someone please explain how to download it or give me a link or something? Thank you in advance!

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  • Internet Explorer table 1 pixel spacing problem

    - by Dennis G.
    I've found a strange problem with Internet Explorer related to table spacing and cannot find a way to work around it. An empty table results in a single pixel white space with Internet Explorer (6 and 7, 8 not yet tested), while all other browsers ignore the empty table. Here's a picture of the problem: And here is the minimum HTML code to reproduce the issue (please note that there are more margin/padding css attributes and table attributes specified than really needed, I just tested if this fixes IE's behavior): <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <body> <div style="width: 200px; border: 1px black solid"> <table border="0" cellspacing="0" cellpadding="0" style="margin: 0pt; padding: 0pt; border-collapse: collapse;"> <tr> <td style="padding: 0; margin: 0"> </td> </tr> </table> <div style="background: red"> Test </div> </div> </body> </html> I'm not using an empty table as specified in the example above, but this was the minimum code that displays this behavior. Any ideas on how to fix this and remove the white space with IE?

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  • Data historian queries

    - by Scott Dennis
    Hi, I have a table that contains data for electric motors the format is: DATE(DateTime) | TagName(VarChar(50) | Val(Float) | 2009-11-03 17:44:13.000 | Motor_1 | 123.45 2009-11-04 17:44:13.000 | Motor_1 | 124.45 2009-11-05 17:44:13.000 | Motor_1 | 125.45 2009-11-03 17:44:13.000 | Motor_2 | 223.45 2009-11-04 17:44:13.000 | Motor_2 | 224.45 Data for each motor is inserted daily, so there would be 31 Motor_1s and 31 Motor_2s etc. We do this so we can trend it on our control system displays. I am using views to extract last months max val and last months min val. Same for this months data. Then I join the two and calculate the difference to get the actual run hours for that month. The "Val" is a nonresetable Accumulation from a PLC(Controller). This is my query for Last months Max Value: SELECT TagName, Val AS Hours FROM dbo.All_Data_From_Last_Mon AS cur WHERE (NOT EXISTS (SELECT TagName, Val FROM dbo.All_Data_From_Last_Mon AS high WHERE (TagName = cur.TagName) AND (Val > cur.Val))) This is my query for Last months Max Value: SELECT TagName, Val AS Hours FROM dbo.All_Data_From_Last_Mon AS cur WHERE (NOT EXISTS (SELECT TagName, Val FROM dbo.All_Data_From_Last_Mon AS high WHERE (TagName = cur.TagName) AND (Val < cur.Val))) This is the query that calculates the difference and runs a bit slow: SELECT dbo.Motors_Last_Mon_Max.TagName, STR(dbo.Motors_Last_Mon_Max.Hours - dbo.Motors_Last_Mon_Min.Hours, 12, 2) AS Hours FROM dbo.Motors_Last_Mon_Min RIGHT OUTER JOIN dbo.Motors_Last_Mon_Max ON dbo.Motors_Last_Mon_Min.TagName = dbo.Motors_Last_Mon_Max.TagName I know there is a better way. Ultimately I just need last months total and this months total. Any help would be appreciated. Thanks in advance

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  • Howt o get the t-sql statements being used to Update a DataSet

    - by Dennis
    I've a c# DataSet object with one table in it, and put some data in it and i've made some changes to that dataset (by code). Is there a way to get the actual t-sql queries this dataset will perform on the sql server when I update the dataset to the database with code that looks something like this: var dataAdapter = new SqlDataAdapter(cmdText, connection); var affected = dataAdapter.Update(updatedDataSet); I want to know what queries this dataset will fire to the database so I can log these changes to a logfile in my c# program.

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  • Project Euler, Problem 10 java solution not working

    - by Dennis S
    Hi, I'm trying to find the sum of the prime numbers < 2'000'000. This is my solution in java but I can't seem get the correct answer. Please give some input on what could be wrong and general advice on the code is appreciated. Printing 'sum' gives: 1308111344, which is incorrect. /* The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17. Find the sum of all the primes below two million. */ class Helper{ public void run(){ Integer sum = 0; for(int i = 2; i < 2000000; i++){ if(isPrime(i)) sum += i; } System.out.println(sum); } private boolean isPrime(int nr){ if(nr == 2) return true; else if(nr == 1) return false; if(nr % 2 == 0) return false; for(int i = 3; i < Math.sqrt(nr); i += 2){ if(nr % i == 0) return false; } return true; } } class Problem{ public static void main(String[] args){ Helper p = new Helper(); p.run(); } }

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  • Rails: three most recent records by unique belongs_to associated record

    - by Dennis Collective
    class User has_many :comments end class Comment belongs_to :user named_scope :recent, :order => 'comments.created_at DESC' named_scope :limit, lambda { |limit| {:limit => limit}} named_scope :by_unique_users end what would I put in the :by_unique_users so that I can do Comment.recent.by_unique_users.limit(3), and only get one comment per user on sqlite named_scope :by_unique_user, :group = "user_id" works, but makes it freak out on postgres, which is deployed on production PGError: ERROR: column "comments.id" must appear in the GROUP BY clause or be used in an aggregate function

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  • Set service dependencies after install

    - by Dennis
    I have an application that runs as a Windows service. It stores various things settings in a database that are looked up when the service starts. I built the service to support various types of databases (SQL Server, Oracle, MySQL, etc). Often times end users choose to configure the software to use SQL Server (they can simply modify a config file with the connection string and restart the service). The problem is that when their machine boots up, often times SQL Server is started after my service so my service errors out on start up because it can't connect to the database. I know that I can specify dependencies for my service to help guide the Windows service manager to start the appropriate services before mine. However, I don't know what services to depend upon at install time (when my service is registered) since the user can change databases later on. So my question is: is there a way for the user to manually indicate the service dependencies based on the database that they are using? If not, what is the proper design approach that I should be taking? I've thought about trying to do something like wait 30 seconds after my service starts up before connecting to the database but this seems really flaky for various reasons. I've also considered trying to "lazily" connect to the database; the problem is that I need a connection immediately upon start up since the database contains various pieces of vital info that my service needs when it first starts. Any ideas?

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  • How to open a pdf on the iPad from an AIR for iOS app

    - by Dennis Flood
    I am making an AIR for iOS app that can download pdfs. I do not want to display the pdf in the app itself but want the default pdf-viewer (iBooks) to launch and show the pdf. How can this be done. I am aware that navigateToURL can be used to open a file with the uri scheme of iBooks. But i dont know how to tell iBooks to look in the app-directory of my app. (Or is there some secret directory to place the file in from within the app - where iBooks can find it) Any pointers or help would be greatly appreciated as this is somewhat of a show stopper.

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  • I still can't ask the question I want to ask! [closed]

    - by Dennis
    Possible Duplicate: Unable to post question despite having no hyperlinks I'm trying to leave a real question but I keep getting this error: We're sorry, but as a spam prevention mechanism, new users can only post a maximum of one hyperlink. Earn 10 reputation to post more hyperlinks. I have removed all the hyper links in the question but I'm still getting the error. Is there someone I can email the code to so we can figure out what the problem is? And I really didn't appreciate the smart ass comment left by whom ever close my last question.

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