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  • odd behavior with java collections of parameterized Class objects

    - by Paul
    Ran into some questionable behavior using lists of parameterized Class objects: ArrayList<Class<String>> classList = new ArrayList<Class<String>>(); classList.add(Integer.class); //compile error Class intClass = Integer.class; classList.add(intClass); //legal apparently, as long as intClass is not parameterized Found the same behavior for LinkedList, haven't tried other collections. Is it like this for a reason? Or have I stumbled on something?

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  • C++ STL: Trouble with iterators

    - by Rosarch
    I'm having a beginner problem: bool _isPalindrome(const string& str) { return _isPalindrome(str.begin(), str.end()); // won't compile } bool _isPalindrome(string::iterator begin, string::iterator end) { return begin == end || *begin == *end && _isPalindrome(++begin, --end); } What am I doing wrong here? Why doesn't str.begin() get type checked to be a string::iterator?

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  • Determining if an unordered vector<T> has all unique elements

    - by Hooked
    Profiling my cpu-bound code has suggested I that spend a long time checking to see if a container contains completely unique elements. Assuming that I have some large container of unsorted elements (with < and = defined), I have two ideas on how this might be done: The first using a set: template <class T> bool is_unique(vector<T> X) { set<T> Y(X.begin(), X.end()); return X.size() == Y.size(); } The second looping over the elements: template <class T> bool is_unique2(vector<T> X) { typename vector<T>::iterator i,j; for(i=X.begin();i!=X.end();++i) { for(j=i+1;j!=X.end();++j) { if(*i == *j) return 0; } } return 1; } I've tested them the best I can, and from what I can gather from reading the documentation about STL, the answer is (as usual), it depends. I think that in the first case, if all the elements are unique it is very quick, but if there is a large degeneracy the operation seems to take O(N^2) time. For the nested iterator approach the opposite seems to be true, it is lighting fast if X[0]==X[1] but takes (understandably) O(N^2) time if all the elements are unique. Is there a better way to do this, perhaps a STL algorithm built for this very purpose? If not, are there any suggestions eek out a bit more efficiency?

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  • Determing if an unordered vector<T> has all unique elements

    - by Hooked
    Profiling my cpu-bound code has suggested I that spend a long time checking to see if a container contains completely unique elements. Assuming that I have some large container of unsorted elements (with < and = defined), I have two ideas on how this might be done: The first using a set: template <class T> bool is_unique(vector<T> X) { set<T> Y(X.begin(), X.end()); return X.size() == Y.size(); } The second looping over the elements: template <class T> bool is_unique2(vector<T> X) { typename vector<T>::iterator i,j; for(i=X.begin();i!=X.end();++i) { for(j=i+1;j!=X.end();++j) { if(*i == *j) return 0; } } return 1; } I've tested them the best I can, and from what I can gather from reading the documentation about STL, the answer is (as usual), it depends. I think that in the first case, if all the elements are unique it is very quick, but if there is a large degeneracy the operation seems to take O(N^2) time. For the nested iterator approach the opposite seems to be true, it is lighting fast if X[0]==X[1] but takes (understandably) O(N^2) time if all the elements are unique. Is there a better way to do this, perhaps a STL algorithm built for this very purpose? If not, are there any suggestions eek out a bit more efficiency?

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  • iTextSharp error - cannot convert type 'Collections.Generic.List' to 'iTextSharp.text.Element'

    - by mike
    I am trying to export pdf file using aspx and c#. I got the following error. Cannot implicitly convert type 'System.Collections.Generic.List'' to 'iTextSharp.text.Element' I have the following code using iTextSharp.text; using iTextSharp.text.pdf; using iTextSharp.text.html.simpleparser; StringBuilder strB = new StringBuilder(); document.Open(); if (text.Length.Equals(0))//export the text { GridView1.DataBind(); using (StringWriter sWriter = new StringWriter(strB)) { using (HtmlTextWriter htWriter = new HtmlTextWriter(sWriter)) { GridView1.RenderControl(htWriter); } } } else //export the grid { strB.Append(text); } using (TextReader sReader = new StringReader(strB.ToString())) { StyleSheet styles = new StyleSheet(); List<Element> list = new List<Element>(); list = HTMLWorker.ParseToList(sReader, styles); foreach (IElement elm in list) { document.Add(elm); } } I got the error in this line: list = HTMLWorker.ParseToList(sReader, styles); It's the first time that I am trying to export pdf files. I tried to cast the list element , however this did not solve my error. Any advice would be helpful!!!

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  • Validation Summary for Collections

    - by Myster
    Hi All, EDIT: upgraded this question to MVC 2.0 With asp.net MVC 2.0 is there an existing method of creating Validation Summary that makes sense for models containing collections? If not I can create my own validation summary Example Model: public class GroupDetailsViewModel { public string GroupName { get; set; } public int NumberOfPeople { get; set; } public List<Person> People{ get; set; } } public class Person { [Required(ErrorMessage = "Please enter your Email Address")] [RegularExpression(@"^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$", ErrorMessage = "Please enter a valid Email Address")] public string EmailAddress { get; set; } [Required(ErrorMessage = "Please enter your Phone Number")] public string Phone { get; set; } [Required(ErrorMessage = "Please enter your First Name")] public string FirstName { get; set; } [Required(ErrorMessage = "Please enter your Last Name")] public string LastName { get; set; } } The existing summary <%=Html.ValidationSummary %> if nothing is entered looks like this. The following error(s) must be corrected before proceeding to the next step * Please enter your Email Address * Please enter your Phone Number * Please enter your First Name * Please enter your Last Name * Please enter your Email Address * Please enter your Phone Number * Please enter your First Name * Please enter your Last Name The design calls for headings to be inserted like this: The following error(s) must be corrected before proceeding to the next step Person 1 * Please enter your Email Address * Please enter your Phone Number * Please enter your First Name * Please enter your Last Name Person 2 * Please enter your Email Address * Please enter your Phone Number * Please enter your First Name * Please enter your Last Name

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  • Essence of BiMap in Google collections

    - by littleEinstein
    I am still quite puzzled at the BiMap in Google collections/Guava. It was claimed that The two bimaps are backed by the same data; any changes to one will appear in the other. I browsed through the source code, and I found the use of delegate in ForwardingMap. But in any actually subclass of StandardBiMap, I do see the data are put into both the forward and reverse map. So what is the essence, and why it claims to have saved space by keeping only one copy of the data? Is it just the actual objects are one set, but two distinct sets of references to these objects are still needed, one set maintained in forward map, and the other in reverse map? private V putInBothMaps(K key, V value, boolean force) { boolean containedKey = containsKey(key); if (containedKey && Objects.equal(value, get(key))) { return value; } if (force) { inverse().remove(value); } else if (containsValue(value)) { throw new IllegalArgumentException( "value already present: " + value); } V oldValue = super.put(key, value); updateInverseMap(key, containedKey, oldValue, value); return oldValue; }

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  • Date Filtered Collections without Functions

    - by madcapnmckay
    Hi, I have an entity similar to the below: public class Entity { public List<DateItem> PastDates { get; set; } public List<DateItem> FutureDates { get; set; } } public class DateItem { public DateTime Date { get; set; } /* * Other Properties * */ } Where PastDates and FutureDates are both mapped to the same type/table. I have been trying to find a way to have the Past and Future properties mapped automagically by Nhibernate. The closest I came was where clause on the mapping as follows HasMany(x => x.PastDates) .AsBag().Cascade .AllDeleteOrphan() .KeyColumnNames.Add("EventId").Where("Date < currentdate()") .Inverse(); Where currentdate is a UDF. I do not want to have these database specific functions if I can avoid it, mostly because i can't then test my DAL with SQLite as it doesn't support functions or stored procedures. At the moment I am building the past and future collections using Criteria and adding to my DTO manually. Anyone know how this could be achieved without using any UDFs? Many thanks,

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  • ArrayList<Int> Collections.Sort and LineNumberReader Help How to

    - by user1819551
    I have a issue i can't get it to work now let going to the point a explain in the code thanks. This is my class: what I want to do is insert the Integers sort the list and buffer writer in a column with out coma. Now I getting this: [1110018, 1110032, 1110056, 1110059, 1110063, 1110085, 1110096, 1110123, 1110125, 1110185, 1110456, 1110459] I want like this: 111xxxxx 111xxxx xxxx....... I can't do it in single array, have to be in ArrayList. This is my collecting: list.addNumbers(numbers); list.display(); This is my writer: Is buffered coma.write("\n"+list.display()); coma.flush();<br/> Here is my class: public class IdCount {<br/> private ArrayList<Integer> properNumber = new ArrayList<>(); public void addNumbers(Integer numbers) { properNumber.add(numbers); Collections.sort(properNumber); } public String display() { //(I try .toString() Not work) return properNumber.toString(); } My second issue is LineNumberReader: This is my collecting and my writing: try { Reader input = new BufferedReader( new FileReader(inputFile)); try (Scanner in = new Scanner(input)) { while (in.hasNext()) { //(More Code) asp = new LineNumberReader(input); int rom = 0; while (asp.readLine()!=null){ rom++; } System.out.println(rom); coma.write(rom); This one will not write anything an my System Print give me only 12 0 in column.

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  • Automapping Collections

    - by vaibhav
    I am using Automapper for mapping my domain model and DTO. When I map Mapper.Map<SiteDTO, SiteEntity> it works fine. But when I use collections of the same entities, it doesn't map. Mapper.Map<Collection<SiteEntity>, Collection<SiteDTO>>(siteEntityCollection); AS per Automapper Wiki, it says the lists implementing ICollection would be mapped, I am using Collection that implements ICollection, but automapper doesn't map it. Am I doing something wrong. public class SiteEntity //SiteDTO has exactly the same properties, so I am not posting it here. { public int SiteID { get; set; } public string Code { get; set; } public string Name { get; set; } public byte Status { get; set; } public int ModifiedBy { get; set; } public DateTime ModifiedDate{ get; set; } public long TimeStamp{ get; set; } public string Description{ get; set; } public string Notes{ get; set; } public ObservableCollection<AreaEntity> Areas{ get; set; } }

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  • Synchronize write to two collections

    - by glaz666
    I need to put some value to maps if it is not there yet. The key-value (if set) should always be in two collections (that is put should happen in two maps atomically). I have tried to implement this as follows: private final ConcurrentMap<String, Object> map1 = new ConcurrentHashMap<String, Object>(); private final ConcurrentMap<String, Object> map2 = new ConcurrentHashMap<String, Object>(); public Object putIfAbsent(String key) { Object retval = map1.get(key); if (retval == null) { synchronized (map1) { retval = map1.get(key); if (retval == null) { Object value = new Object(); //or get it somewhere synchronized (map2) { map1.put(key, value); map2.put(key, new Object()); } retval = value; } } } return retval; } public void doSomething(String key) { Object obj1 = map1.get(key); Object obj2 = map2.get(key); //do smth } Will that work fine in all cases? Thanks

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  • Is there a general concrete implementation of a KeyedCollection?

    - by CodeSavvyGeek
    The System.Collections.ObjectModel.KeyedCollection class is a very useful alternative to System.Collections.Generic.Dictionary, especially when the key data is part of the object being stored or you want to be able to enumerate the items in order. Unfortunately, the class is abstract, and I am unable to find a general concrete implementation in the core .NET framework. The Framework Design Guidlines book indicates that a concrete implementation should be provided for abstract types (section 4.4 Abstract Class Design). Why would the framework designers leave out a general concrete implementation of such a useful class, especially when it could be provided by simply exposing a constructor that accepts and stores a Converter from the item to its key: public class ConcreteKeyedCollection : KeyedCollection { private Converter getKeyForItem = null; public GenericKeyedCollection(Converter getKeyForItem) { if (getKeyForItem == null) { throw new ArgumentNullException("getKeyForItem"); } this.getKeyForItem = getKeyForItem; } protected override TKey GetKeyForItem(TItem item) { return this.getKeyForItem(item); } }

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  • Quaere - Anyone using it yet? (LINQ to Objects for Java)

    - by Marty Pitt
    Hi there I'm a .NET guy originally, working in Java recently, and finding I'm really missing LINQ to Objects, specifically for performing filtering against collections. A few people here on Stack Overflow have answered the "LINQ for Java?" question with a single word : Quaere However, on the site it clearly states "Pre-Beta", and there's been no commits to their code for over a year, so I'm guessing the project is pretty much dead. Is anyone actually using this, and / or have any experience with it? The second most common answer appears to be "use Google Collections". Is this the most appropriate Java way? Cheers Marty

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  • ASP.NET handling button click event before OnPreInit

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

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  • Java: Set<E> collection, where items are identified by its class

    - by mschayna
    I need Set collection, where its items will be identified by items class. Something like ReferenceIdentityMap from Appache Collections, but on class scope i.e. two different instances of same class must be identified as same in this collection. You know, it is a violation of equals()/hashCode() identity principle but in occasional use it makes sense. I have done this in simple class backing with Map<Class<? extends E>, E>, but due to simplicity it doesn't implement Set<E>. There may be a more elegant solution, decorator of any Set<E> would be great. Is there any implementation of such collection there (Apache/Google/something/... Collections)?

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  • Intersection between sets containing different types of variables

    - by Gacek
    Let's assume we have two collections: List<double> values List<SomePoint> points where SomePoint is a type containing three coordinates of the point: SomePoint { double X; double Y; double Z; } Now, I would like to perform the intersection between these two collections to find out for which points in points the z coordinate is eqal to one of the elements of values I created something like that: HashSet<double> hash = new HashSet<double>(points.Select(p=>p.Z)); hash.IntersectWith(values); var result = new List<SomePoints>(); foreach(var h in hash) result.Add(points.Find(p => p.Z == h)); But it won't return these points for which there is the same Z value, but different X and Y. Is there any better way to do it?

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  • sql to xml using linq - nested collections

    - by nelsonwebs
    I have a table of data that looks something like this. name, hour, price1, price2, price3, price4, price5 fred, 3, 12.5, 13.5, 14, 15, 16 dave, 6, 8, 12, 18, 20.2, 25 fred, 6, 10, 11, 14, 15, 19.7 This table needs to be output to an xml file that looks like this. <timeCost> <person name="fred"> <time hour="5"> <cost price="12.5" /> <cost price="13.5" /> <cost price="14" /> <cost price="15" /> <cost price="16" /> </time> <time hour="6"> <cost price="10" /> <cost price="11" /> <cost price="14" /> <cost price="15" /> <cost price="19.7" /> </time> </person> <person name="dave"> <time hour="6"> <cost price="8" /> <cost price="12" /> <cost price="18" /> <cost price="20.2" /> <cost price="25" /> </time> </person> </timeCost> I have a linq query to get the data from SQL something like this. // initialize data context var people = from p in dc.people orderby p.name, p.hour select p; However, I'm having trouble writing the xml out using linq (csharp). Specifically, the problem is I don't know how to deal with having multiple time nodes under each name node (nested loops/collections). How can this be done? This is a sql 08 ent db if it matters to anyone.

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  • JAX-WS wsgen and collections of collections: wsgen broken?

    - by ayang
    I've been playing around with "bottom-up" JAX-WS and have come across something odd when running wsgen. If I have a service class that does something like: @WebService public class Foo { public ArrayList<Bar> getBarList(String baz) { ... } } then running wsgen gets me a FooService_schema1.xsd that has something like this: <xs:complexType name="getBarListResponse"> <xs:sequence> <xs:element name="return" type="tns:bar" minOccurs="0" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> which seems reasonable. However, if I want a collection of collections like: public BarCollection getBarCollection(String baz) { ... } // BarCollection is just a container for an ArrayList<Bar> then the generated schema ends up with stuff like: <xs:complexType name="barCollection"> <xs:sequence/> </xs:complexType> <xs:complexType name="getBookCollectionsResponse"> <xs:sequence> <xs:element name="return" type="tns:barCollection" minOccurs="0" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> An empty sequence is not what I had in mind at all. My original approach was to go with: public ArrayList<ArrayList<Bar>> getBarLists(String baz) { ... } but that ends up with a big chain of complexTypes that just wind up with an empty sequence at the end as well: <xs:complexType name="getBarListsResponse"> <xs:sequence> <xs:element name="return" type="tns:arrayList" minOccurs="0" maxOccurs="unbounded"/> </xs:sequence> </xs:complexType> <xs:complexType name="arrayList"> <xs:complexContent> <xs:extension base="tns:abstractList"> <xs:sequence/> </xs:extension> </xs:complexContent> </xs:complexType> <xs:complexType name="abstractList" abstract="true"> <xs:complexContent> <xs:extension base="tns:abstractCollection"> <xs:sequence/> </xs:extension> </xs:complexContent> </xs:complexType> <xs:complexType name="abstractCollection" abstract="true"> <xs:sequence/> </xs:complexType> Am I missing something or is this a known hole in wsgen? JAXB? Andy

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  • Model self referential collections in Rails

    - by Najitaka
    I have written an application for an online clothing store in Rails 2.3.5. I want to show related Products when a customer views the Product Detail page. For example, if the customer views the detail page for a suit, I'd like to display the accessory products that match the dress such as a vest, shoes, and belt. I have named the related products an Ensemble. However, the vest, shoes, and belts are also Products which is what has me struggling. I have it working as follows but I know it's not the Rails way. I have a Products table for all of the products. Not important here but I also have a ProductDetails table. I have an Ensembles table that has the following columns: product_id - the main or origination product, the one displayed on the detail page outfit_id - the related or accessory product In setting up the data, on the Products list, for each Product I have an Ensemble link. This link takes you to the index action in the Ensembles controller. Using the id from the "main" Product, I find all of the associated Ensemble rows by product_id or I create a new ensemble and assign the id from the main product as the product_id. I'd like to just be able to do @product.related_products to get an Ensemble collection. Also on the index page I list the columns of the main product so the user can be sure their main product was the one they selected from the list. I also have a select list of the other products, with an Add to Ensemble action. Finally on the same index page, I have a table that displays the products that are already in the ensemble and in that list each row has a destroy link to remove a particular product from the ensemble. It would be nice if given a single Ensemble row @ensemble I could do @ensemble.product to get the Product related to the outfit_id of the ensemble row. I've got it working without associations but I have to run queries in the controller to build my own @product, @ensemble, and @ensembles collections. Also the only way I found to destroy an ensemble row is by Ensemble.connection.delete(sql to delete), simple @ensemble.destroy doesn't work. Anyone know how I would set up the associations or have a link to a site explaining a similar setup. None of the examples I found use the same table. They have A related to B through C. I want A related to other A through B.

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  • The model item passed into the dictionary is of type 'System.Collections.Generic.Lis

    - by mazhar
    Calling Index view is giving me this very very annoying error . Can anybody tell me what to do about it Error: The model item passed into the dictionary is of type 'System.Collections.Generic.List1[MvcApplication13.Models.Groups]', but this dictionary requires a model item of type 'MvcApplication13.Helpers.PaginatedList1[MvcApplication13.Models.Groups]'. public ActionResult Index(int? page) { const int pageSize = 10; var group =from p in _db.Groups orderby p.int_GroupId select p; var paginatedGroup = group.Skip((page ?? 0) * pageSize).Take(pageSize).ToList(); return View(paginatedGroup); } View: <%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage" % Index <h2>Index</h2> <table> <tr> <th></th> <th> int_GroupId </th> <th> vcr_GroupName </th> <th> txt_GroupDescription </th> <th> bit_Is_Deletable </th> <th> bit_Active </th> <th> int_CreatedBy </th> <th> dtm_CreatedDate </th> <th> int_ModifiedBy </th> <th> dtm_ModifiedDate </th> </tr> <% foreach (var item in Model) { %> <tr> <td> <%= Html.ActionLink("Edit", "Edit", new { id=item.int_GroupId }) %> | <%= Html.ActionLink("Details", "Details", new { id=item.int_GroupId })%> | <%= Html.ActionLink("Delete", "Delete", new { id=item.int_GroupId })%> </td> <td> <%= Html.Encode(item.int_GroupId) %> </td> <td> <%= Html.Encode(item.vcr_GroupName) %> </td> <td> <%= Html.Encode(item.txt_GroupDescription) %> </td> <td> <%= Html.Encode(item.bit_Is_Deletable) %> </td> <td> <%= Html.Encode(item.bit_Active) %> </td> <td> <%= Html.Encode(item.int_CreatedBy) %> </td> <td> <%= Html.Encode(String.Format("{0:g}", item.dtm_CreatedDate)) %> </td> <td> <%= Html.Encode(item.int_ModifiedBy) %> </td> <td> <%= Html.Encode(String.Format("{0:g}", item.dtm_ModifiedDate)) %> </td> </tr> <% } %> </table> <% if (Model.HasPreviousPage) { % <%= Html.RouteLink("<<<", "UpcomingDinners", new { page = (Model.PageIndex-1) }) % <% } % <% if (Model.HasNextPage) { % <%= Html.RouteLink("", "UpcomingDinners", new { page = (Model.PageIndex + 1) }) % <% } % <p> <%= Html.ActionLink("Create New", "Create") %> </p>

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  • C++: Appending a vector to a vector

    - by sub
    Assuming I have 2 STL vectors: vector<int> a; vector<int> b; Let's also say the both have around 30 elements. How do I add the vector b to the end of vector a? The dirty way would be iterating through b and adding each element via push_back, though I wouldn't like to do that!

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  • What C++ pitfalls should I avoid ?

    - by Craig H
    I remember first learning about vectors in the STL and after some time, I wanted to use a vector of bools for one of my projects. After seeing some strange behavior and doing some research, I learned that a vector of bools is not really a vector of bools. Anyone out there have any other common pitfalls to avoid in C++?

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  • Do I need to check capacity before adding an element to a vector in c++ ?

    - by Cassie
    Hi dear all, I am a newbie to c++ STL vectors so sorry for silly questions in advence. :) In my program, I have a vector which needs to store unknown number of elements. Do I have to check if the vector has achieved its max_size before adding an new element to it ? Will a c++ compiler throw an exception automatically when a program tries to add elements to a full vector ? Thank you very much, Cassie

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