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  • How do I iterate over a tuple

    - by Caligo
    How can I iterate over a tuple starting from, say, index 1 to 2? The following doesn't work. using boost::fusion::cons; typedef cons<A, cons<B, cons<C, cons<D> > > > MyTuple; MyTuple tuple_; template <class T> struct DoSomething{ DoSomething(T& t) : t_(&t){ } template <class U> void operator()(U u){ boost::fusion::at<mpl::int_<u> >(*t_); } T* t_; }; boost::mpl::for_each< boost::mpl::range_c<int, 1, 3> >( DoSomething<MyTuple>(tuple_) );

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  • ActionScript: Using 'in' on protected/private variables?

    - by David Wolever
    Is there any way to mimic the in operator, but testing for the existence of protected or private fields? For example, this: <mx:Script><![CDATA[ public var pub:Boolean = true; protected var prot:Boolean = true; private var priv:Boolean = true; ]]></mx:Script> <mx:creationComplete><![CDATA[ for each (var prop in ["pub", "prot", "priv", "bad"]) trace(prop + ":", prop in this); ]]></mx:creationComplete> Will trace: pub: true prot: false priv: false bad: false When I want to see: pub: true prot: true priv: true bad: false

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  • C++: Vector3 type "wall" ?

    - by anon
    Say I have: class Vector3 { float x, y, z; ... bunch of cuntions .. static operator+(const Vector3&, const Vector3); }; Now, suppose I want to have classes: Position, Velocity, that are exactly like Vector3 (basically, I want typedef Vector3 Position; typedef Vector3 Velocity; Except, given: Position position; Vector3 vector3; Velocity velocity; I want to make sure the following can't happen: position + vector3; vector3 + velocity; velocity + position; What is the best way to achieve this?

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  • Any way to make a generic List where I can add a type AND a subtype?

    - by user383178
    I understand why I cannot do the following: private class Parent { }; private class Child extends Parent { }; private class GrandChild extends Child { }; public void wontCompile(List<? extends Parent> genericList, Child itemToAdd) { genericList.add(itemToAdd); } My question is there ANY practical way to have a typesafe List where you can call add(E) where E is known to be only a Parent or a Child? I vaguely remember some use of the "|" operator as used for wildcard bounds, but I cannot find it in the spec... Thanks!

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  • C pointer question, dereferencing crash

    - by skynorth
    Why do this work? int *var; while(scanf("%d", &var) && *var != 0) printf("%d \n", var); While this does not? int *var; while(scanf("%d", &var) && var != 0) printf("%d \n", var); Doesn't * (dereference operator) give you the value pointed by the pointer? So why does *var != 0 crash the program, while var != 0 does not?

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  • How to insert into std::map.

    - by Knowing me knowing you
    In code below: map<string,vector<int>> create(ifstream& in, const vector<string>& vec) { /*holds string and line numbers into which each string appears*/ typedef map<string,vector<int>> myMap; typedef vector<string>::const_iterator const_iter; myMap result; string tmp; unsigned int lineCounter = 0; while(std::getline(in,tmp)) { const_iter beg = vec.begin(); const_iter end = vec.end(); while (beg < end) { if ( tmp.find(*beg) != string::npos) { result[*beg].push_back(lineCounter);//THIS IS THE LINE I'M ASKING FOR } ++beg; } ++lineCounter; } return result; } How should I do it (check line commented in code) if I want to use insert method of map instead of using operator[]? Thank you.

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  • How to retrieve all keys (or values) from a std::map?

    - by Owen
    This is one of the possible ways I come out: struct RetrieveKey { template <typename T> typename T::first_type operator()(T keyValuePair) const { return keyValuePair.first; } }; map<int, int> m; vector<int> keys; // Retrieve all keys transform(m.begin(), m.end(), back_inserter(keys), RetrieveKey()); // Dump all keys copy(keys.begin(), keys.end(), ostream_iterator<int>(cout, "\n")); Of course, we can also retrieve all values from the map by defining another functor RetrieveValues. Is there any other way to achieve this easily? (I'm always wondering why std::map does not include a member function for us to do so.)

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  • How do I put logic in a View a scope or method in a Model?

    - by Angela
    I have the following in the view: <% unless contact_email.statuses.empty?%> (<%= contact_email.statuses.find(:last).status%>) <% end %> contact_email is an instance of a specific model. Could I do something like this? class ContactEmail < ActiveRecord::Base attr_accessible :contact_id, :email_id, :status, :subject, :body, :date_created, :date_sent def status unless contact_email.statuses.empty? contact_email.statuses.find(:last).status end end end is there a better way to do this? is there a way to use the || operator for a default if empty? Basically, I would like to be able to do the following in the View: <%= contact_email.status = IF there is a value, then display it, if not, show nothing.

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  • How should I get Xcode to link an iOS project that uses a C++ static library

    - by user1681572
    Using Xcode, I've written a Cocoa Touch static library, mainly in C++. It exposes a C interface for the benefit of Objective-C client code. I have a client iOS app that uses it, and everything works and runs as expected, except that I found I needed to include a minimal .cpp file in the client project to get the link to succeed. Otherwise I get C++-related unresolved symbols, e.g. operator new(unsigned long). The above hack is easy and effective, and so I guess I'm not breaking any laws, but is there a proper way to eliminate my linker errors?

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  • What does it mean when a Perl method returns a "hashref"?

    - by Uri
    I'm trying to decrypt a Perl code which I'm not familiar with, somehow related to HashRef. I'm using Amazon::S3, but my question is a general Perl question. See the code below: use Amazon::S3; my $s3 = Amazon::S3->new( ... ); my $response = $s3->buckets; Documentation (here) sais, about s3-buckets: Returns undef on error, else HASHREF of results The following line is working for me, but I don't understand why: for $b in ( @ { $response->{buckets} } ) { print "bucket: " . $b->bucket . "\n"; } I'm Puzzled by each operator on the first line. What type exactly are $response, $respone->{bucket}. Looks like the expression within the for is an array, but I don't understand this syntax: @{ ... }?

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  • Using Linq to filter parents by their children

    - by Nick L
    Having some problems with my Silverlight app (with RIA services) filtering my results. The idea is on the client I set up the EntityQuery and its filters and call load. However this isn't working for me. Heres my code. public void FireQuery(string filterValue) { EntityQuery<Parent> query = m_ParentDomainContext.GetParentQuery(); query = query.Where(p => p.Children.Any(c => c.Name.Contains(filterValue))); m_ParentDomainContext.Load(query, Query_Completed, null); } Compiles just fine, however, runtime I get "Query operator 'Any' is not supported." Exception. Does anyone know of a good way to filter like this? Again, I'm looking for a way to set this up on the client.

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  • Retrieving a single Guid in CRM 4.0

    - by user1746560
    I'm new to CRM (version 4.0) and i'm trying to return a 'yearid' guide based on a given year (which is also stored in the entity).So far i've got: public static Guid GetYearID(string yearName) { ICrmService service = CrmServiceFactory.GetCrmService(); // Create the query object. QueryExpression query = new QueryExpression("year"); ColumnSet columns = new ColumnSet(); columns.AddColumn("yearid"); query.ColumnSet = columns; FilterExpression filter = new FilterExpression(); filter.FilterOperator = LogicalOperator.And; filter.AddCondition(new ConditionExpression { AttributeName = "yearName", Operator = ConditionOperator.Equal, Values = new object[] { yearName} }); query.Criteria = filter; } But my questions are: A) What code do in addition to this to actually store the Guid? B) Is using a QueryExpression the most efficient way to do this?

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  • C++ How do you set an array of pointers to null in an initialiser list like way?

    - by boredjoe
    I am aware you cannot use an initialiser list for an array. However I have heard of ways that you can set an array of pointers to NULL in a way that is similar to an initialiser list. I am not certain how this is done. I have heard that a pointer is set to NULL by default, though I do not know if this is guaranteed/ in the C++ standard. I am also not sure if initialising through the new operator compared to normal allocation can make a difference too.

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  • fastest method for minimum of two numbers

    - by user85030
    I was going through mit's opencourseware related to performance engineering. The quickest method (requiring least number of clock cycles) for finding the minimum of two numbers(say x and y) is stated as: min= y^((x^y) & -(x<y)) The output of the expression x < y can be 0 or 1 (assuming C is being used) which then changes to -0 or -1. I understand that xor can be used to swap two numbers. Questions: 1. How is -0 different from 0 and -1 in terms of binary? 2. How is that result used with the and operator to get the minimum? Thanks in advance.

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  • C++ Iterators and inheritance

    - by jomnis
    Have a quick question about what would be the best way to implement iterators in the following: Say I have a templated base class 'List' and two subclasses "ListImpl1" and "ListImpl2". The basic requirement of the base class is to be iterable i.e. I can do: for(List<T>::iterator it = list->begin(); it != list->end(); it++){ ... } I also want to allow iterator addition e.g.: for(List<T>::iterator it = list->begin()+5; it != list->end(); it++){ ... } So the problem is that the implementation of the iterator for ListImpl1 will be different to that for ListImpl2. I got around this by using a wrapper ListIterator containing a pointer to a ListIteratorImpl with subclasses ListIteratorImpl2 and ListIteratorImpl2, but it's all getting pretty messy, especially when you need to implement operator+ in the ListIterator. Any thoughts on a better design to get around these issues?

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  • calling a java class in a servlet

    - by kawtousse
    hi, in my servlet i called an instance of a class.java( a class that construct an html table) in order to create this table in my jsp. the servlet is like the following: String report=request.getParameter("selrep"); String datev=request.getParameter("datepicker"); String op=request.getParameter("operator"); String batch =request.getParameter("selbatch"); System.out.println("report kind was:"+report); System.out.println("date was:"+datev); System.out.println("operator:"+op); System.out.println("batch:"+batch); if(report.equalsIgnoreCase("Report Denied")) { DeniedReportDisplay rd = new DeniedReportDisplay(); rd.ConstruireReport(); } else if(report.equalsIgnoreCase("Report Locked")) { LockedReportDisplay rl = new LockedReportDisplay(); rl.ConstruireReport(); } request.getRequestDispatcher("EspaceValidation.jsp").forward(request, response); in my jsp i can not display this table even empty or full. note: exemple a class that construct denied Report has this structure: /*constructeur*/ public DeniedReportDisplay() {} /*Methodes*/ @SuppressWarnings("unchecked") public StringBuffer ConstruireReport() { StringBuffer retour=new StringBuffer(); int i = 0; retour.append("<table border = 1 width=900 id=sheet align=left>"); retour.append("<tr bgcolor=#0099FF>" ); retour.append("<label> Denied Report</label>"); retour.append("</tr>"); retour.append("<tr>"); String[] nomCols ={"Nom","Prenom","trackingDate","activity","projectcode","WAName","taskCode","timeSpent","PercentTaskComplete","Comment"}; //String HQL_QUERY = null; for(i=0;i< nomCols.length;i++) { retour.append(("<td bgcolor=#0066CC>")+ nomCols[i] + "</td>"); } retour.append("</tr>"); retour.append("<tr>"); try { s= HibernateUtil.currentSession(); tx=s.beginTransaction(); Query query = s.createQuery("select opcemployees.Nom,opcemployees.Prenom,dailytimesheet.TrackingDate,dailytimesheet.Activity," + "dailytimesheet.ProjectCode,dailytimesheet.WAName,dailytimesheet.TaskCode," + "dailytimesheet.TimeSpent,dailytimesheet.PercentTaskComplete from Opcemployees opcemployees,Dailytimesheet dailytimesheet " + "where opcemployees.Matricule=dailytimesheet.Matricule and dailytimesheet.Etat=3 " + "group by opcemployees.Nom,opcemployees.Prenom" ); for(Iterator it=query.iterate();it.hasNext();) { if(it.hasNext()){ Object[] row = (Object[]) it.next(); retour.append("<td>" +row [0]+ "</td>");//Nom retour.append("<td>" + row [1] + "</td>");//Prenom retour.append("<td>" + row [2] + "</td>");//trackingdate retour.append("<td>" + row [3]+ "</td>");//activity retour.append("<td>" + row [4] +"</td>");//projectcode retour.append("<td>" + row [5]+ "</td>");//waname retour.append("<td>" + row [6] + "</td>");//taskcode retour.append("<td>" + row [7] + "</td>");//timespent retour.append("<td>" + row [8] + "</td>");//perecnttaskcomplete retour.append("<td><input type=text /></td>");//case de commentaire } retour.append("</tr>"); } //terminer la table. retour.append ("</table>"); tx.commit(); } catch (HibernateException e) { retour.append ("</table><H1>ERREUR:</H1>" +e.getMessage()); e.printStackTrace(); } return retour; } thanks for help.

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  • Testing what a String token holds

    - by Yiwei Gao
    I am making a calculator and part of this program takes in user String input and tokenizes it (using my own implementation of a Tokenizer class). So now I have a bunch of Token objects and I would like to test each one of them to see if they hold numbers or operators. Is there a way to test to see if they hold operators (ie. +, -, *, /, =, (, ), etc.) without using if (token.equals("+") || token.equals("-") || ... and so on, for each operator? These Token objects are all of type String.

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  • Casting an object which could be null

    - by DeeMac
    DateTime? testDate = (DateTime?)arrayOfObjects[dateObject]; Does that code look ok? I attempted to use the as operator but I got the 'non-nullable' error. What I'm trying to say is that the object I'm choosing from the array is either DateTime or a null DateTime but either can be assigned to testDate. Doesn't feel right doing it this way, I think I'm missing something obvious. EDIT: I suppose it's the same as the way I could've adapted the as in the following way: DateTime? testDate = arrayOfObjects[dateObject] as DateTime?; Is either line of code the best way of handling potential nulls?

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  • Finding the specific type held in an ArrayList<Object> (ie. Object = String, etc.)

    - by Christopher Griffith
    Say I have an ArrayList that I have cast to an ArrayList of objects. I know that all the objects that were in the ArrayList I cast were of the same type, but not what the type was. Now, if the ArrayList is not empty, I could take one of the objects in it and use the instanceof operator to learn what the actual type is. But what of the case where the ArrayList is empty? How do I determine what type Object actually is then? Is it possible?

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  • How does the stream manipulators work?

    - by Narek
    It is well known that the user can define stream manipulators like this: ostream& tab(ostream & output) { return output<< '\t'; } And this can be used in main() like this: cout<<'a'<<tab<<'b'<<'c'<<endl; Please explain me how does this all work? If operator<< assumes as a second parameter a pointer to the function that takes and returns ostream &, then please explain my why it is necessary? What would be wrong if the function does not take and return ostream & but it was void instead of ostream &? Also it is interesting why “dec”, “hex” manipulators take effect until I don’t change between them, but user defined manipulators should be always used in order to take effect for each streaming?

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  • Using template specialization in C++

    - by user550413
    How can I write a function using template specialization that has 2 different input types and an output type: template <class input1, class input2, class output> and return the sum of the 2 numbers (integers/doubles). However, if I get 2 integers I want to return an integer type but for any other combinations of integer and double I'll always return double. I am trying to do that without using directly the '+' operator but having the next functions instead: double add_double_double(double a, double b) {return (a+b);} double add_int_double(int a, double b) {return ((double)(a)+b);} int add_int_int(int a, int b) {return (a+b);}

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  • What's the simplest way of defining lexicographic comparison for elements of a class?

    - by the_mandrill
    If I have a class that I want to be able to sort (ie support a less-than concept), and it has several data items such that I need to do lexicographic ordering then I need something like this: struct MyData { string surname; string forename; bool operator<(const MyData& other) const { return surname < other.surname || (surname==other.surname && forename < other.forename); } }; This becomes pretty unmanageable for anything with more than 2 data members. Are there any simpler ways of achieving it? The data members may be any Comparable class.

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  • How to stable_sort without copying?

    - by Mehrdad
    Why does stable_sort need a copy constructor? (swap should suffice, right?) Or rather, how do I stable_sort a range without copying any elements? #include <algorithm> class Person { Person(Person const &); // Disable copying public: Person() : age(0) { } int age; void swap(Person &other) { using std::swap; swap(this->age, other.age); } friend void swap(Person &a, Person &b) { a.swap(b); } bool operator <(Person const &other) const { return this->age < other.age; } }; int main() { static size_t const n = 10; Person people[n]; std::stable_sort(people, people + n); }

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  • Mobile web apps - Is this the right approach?

    - by Pasta
    I need to build a cross platform mobile app (iphone, android, etc). The app is for a company like a cellular operator (Tmobile, ATT). The app needs to do the following: Show previous bills (cached so that it does not have to download everytime) Need an internet connection to download newer bills, view recent data, etc. Can I build a mobile web app to handle this? I understand that there is offline storage and iPhone has good support for web apps (full screen, good icons, offline, etc). Will a web app be the best approach to take as the app requires to be online? The app will not be used by lots of people, just customers of the website who don't want to use an existing website. We are all web developers and a mobile web app looks like the best way to approach this.

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  • The Cash or Credit problem

    - by Josh K
    If you go to a store and ask "Cash or Credit?" they might simply say "Yes." This doesn't tell you anything as you posed an OR statement. if(cash || credit) With humans it's possible that they might respond "Both" to that question, or "Only {cash | credit}." Is there a way (or operator) to force the a statement to return the TRUE portions of a statement? For example: boolean cash = true; boolean credit = true; boolean cheque = false; if(cash || credit || cheque ) { // In here you would have an array with cash and credit in it because both of those are true }

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