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Search found 908 results on 37 pages for 'iterator'.

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• How to select a random element in std::set?

  - by dehmann

  How can I select a random element in an std::set? I naively tried this: int GetSample(const std::set<int>& s) { double r = rand() % s.size(); return *(s.begin() + r); // compile error } But the operator+ is not allowed in this way.

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• STL ostream_iterator writes to screen even though I overwrote it?

  - by adam_0

  In my code, I have the following: ostream_iterator<double> doubleWriter(cout, " ~ "); // ... *doubleWriter = 1.1; doubleWriter++; *doubleWriter = 2.2; *doubleWriter = 3.3; // shouldn't 2.2 be overwritten? doubleWriter++; *doubleWriter = 44.2; cout << endl << endl; I expected it to output this: 1.1 ~ 3.3 ~ 44.2 ~ Instead,…

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• Why can't I construct an std::istream_iterator with an unnamed temporary?

  - by Stumped6789

  g++ allows this construction of an istream_iterator from an ifstream instance: std::ifstream ifstr("test.txt"); std::istream_iterator<std::string> iter1(ifstr); ...but it doesn't allow the same construction with an unnamed temporary: std::istream_iterator<std::string> iter2(std::ifstream("test.txt")); This gives: error: no…

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• Custom InputIterator for Boost graph (BGL)

  - by Shadow

  Hi, I have a graph with custom properties to the vertices and edges. I now want to create a copy of this graph, but I don't want the vertices to be as complex as in the original. By this I mean that it would suffice that the vertices have the same indices (vertex_index_t) as they do in the original graph. Instead of doing the copying by hand I…

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• Adding S3 metadata using jets3t

  - by billintx

  I'm just starting to use the jets3t API for S3, using version 0.7.2 I can't seem to save metadata with the S3Objects I'm creating. What am I doing wrong? The object is successfully saved when I putObject, but I don't see the metadata after I get the object. S3Service s3Service = new RestS3Service(awsCredentials); S3Bucket…

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• JGoodies HashMap

  - by JohnMcClane

  Hi, I'm trying to build a chart program using presentation model. Using JGoodies for data binding was relatively easy for simple types like strings or numbers. But I can't figure out how to use it on a hashmap. I'll try to explain how the chart works and what my problem is: A chart consists of DataSeries, a DataSeries consists of…

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• Internal class and access to external members.

  - by Knowing me knowing you

  I always thought that internal class has access to all data in its external class but having code: template<class T> class Vector { template<class T> friend std::ostream& operator<<(std::ostream& out, const Vector<T>& obj); private: T** myData_; std::size_t myIndex_; std::size_t mySize_;…

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• What's the difference between these two calls to a function taking a collection of structural types?

  - by James Moore

  Why does the call to fn(Iterator("foo") compile, but the call to fn(fooIterator) fail with an error "type mismatch; found : Iterator[java.lang.String] required: scala.Iterator[com.banshee.Qx.HasLength]" object Qx { type HasLength = {def length: Int} def fn(xs: Iterator[HasLength]) = 3 var tn =…

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• In C++, how do I get an int index of an iterator?

  - by George

  I need to cout and return a deque element's index that an iterator is pointing to. How do I get an int out of an iterator?

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• Java code optimization on matrix windowing computes in more time

  - by rano

  I have a matrix which represents an image and I need to cycle over each pixel and for each one of those I have to compute the sum of all its neighbors, ie the pixels that belong to a window of radius rad centered on the pixel. I came up with three alternatives: The simplest way, the one that recomputes the…

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• build error with boost spirit grammar (boost 1.43 and g++ 4.4.1) part II

  - by lurscher

  I'm having issues getting a small spirit/qi grammar to compile. i am using boost 1.43 and g++ 4.4.1. the input grammar header: inputGrammar.h #include <boost/config/warning_disable.hpp> #include <boost/spirit/include/qi.hpp> #include <boost/spirit/include/phoenix_core.hpp> #include…

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• Page expired issue with back button and wicket SortableDataProvider and DataTable

  - by David

  Hi, I've got an issue with SortableDataProvider and DataTable in wicket. I've defined my DataTable as such: IColumn<Column>[] columns = new IColumn[9]; //column values are mapped to the private attributes listed in ColumnImpl.java columns[0] = new PropertyColumn(new Model("#"),…

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• Is this a pattern? Should it be?

  - by Arkadiy

  The following is more of a statement than a question - it describes something that may be a pattern. The question is: is this a known pattern? Or, if it's not, should it be? I've had a situation where I had to iterate over two dissimilar multi-layer data structures and copy information from…

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• Could someone tell me the purpose of Inner classes and if iterator pattens should or a good idea to

  - by welcometocanada

  Could someone tell me what the purpose of inner classes are? Also when designing the iterator pattern do we have to use inner classes? Would it be better to use inner classes?

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• What iterator to return for non-existing map How to signkey?

  - by Jack

  I want to have a function which searches for a key in a collection of maps and returns an iterator to the found key. But what should be returned in case the key cannot be found? I cannot return map::end since the collection of maps can be empty. Thanks.

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• Wildcards vs. generic methods

  - by FredOverflow

  Is there any practical difference between the following approaches to print all elements in a range? public static void printA(Iterable<?> range) { for (Object o : range) { System.out.println(o); } } public static <T> void printB(Iterable<T> range) { …

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• Why does Perl's shift complain 'Type of arg 1 to shift must be array (not grep iterator).'?

  - by wes

  I've got a data structure that is a hash that contains an array of hashes. I'd like to reach in there and pull out the first hash that matches a value I'm looking for. I tried this: my $result = shift grep {$_->{name} eq 'foo'} @{$hash_ref->{list}}; But that gives me this error:…

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• Why can't I access a const vector with iterator?

  - by tsubasa

  My example is as below. I found out the problem is with "const" in function void test's parameter. I don't know why the compiler does not allow. Could anybody tell me? Thanks. vector<int> p; void test(const vector<int> &blah) { vector<int>::iterator it; for…

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• In C++, I want to implement a ring iterator for a deque that contains a personally defined class.

  - by George

  I have a function of a "Table" class that should add a player to the table. I decided that if the seat is taken, the function should try and go through all the seats and add the player to the next available seat. How do I implement this in my addPlayer function? int…

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• Is valgrind crazy or is this is a genuine std map iterator memory leak?

  - by Alberto Toglia

  Well, I'm very new to Valgrind and memory leak profilers in general. And I must say it is a bit scary when you start using them cause you can't stop wondering how many leaks you might have left unsolved before! To the point, as I'm not an experienced in c++…

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• Connection and Collection Interfaces in Java

  - by Bhupi

  Which class implements all the Connection Interfaces which are in javax.microedition.io package and how? And in the same way which class implements the some of Collection interfaces like Iterator interface. I saw a code: - Iterator it; ArrayList list =…

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• Should I return iterators or more sophisticated objects?

  - by Erik

  Say I have a function that creates a list of objects. If I want to return an iterator, I'll have to return iter(a_list). Should I do this, or just return the list as it is? My motivation for returning an iterator is that this would keep the interface…

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• New Sample Demonstrating the Traversing of Tree Bindings

  - by Duncan Mills

  A technique that I seem to use a fair amount, particularly in the construction of dynamic UIs is the use of a ADF Tree Binding to encode a multi-level master-detail relationship which is then expressed in the UI in some kind of looping form – usually…

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• The most efficent ways for drawing lines all day long with OpenGL

  - by nkint

  I'd like to put a computer screen that is running an OpenGL programs in a room. It has to run all day long (not in the night). I'd like to draw lines that are slowly fading in the background. The setting is simple: a uniform color background (say,…

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• How do I display a Wicket Datatable, sorted by a specific column by default?

  - by David

  Hello everyone! I have a question regarding Wicket's Datatable. I am currently using DataTable to display a few columns of data. My table is set up as follows: DataTable<Column> dataTable = new DataTable<Column>("columnsTable",…

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