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  • How would I compare two Lists(Of <CustomClass>) in VB?

    - by Kumba
    I'm working on implementing the equality operator = for a custom class of mine. The class has one property, Value, which is itself a List(Of OtherClass), where OtherClass is yet another custom class in my project. I've already implemented the IComparer, IComparable, IEqualityComparer, and IEquatable interfaces, the operators =, <>, bool and not, and overriden Equals and GetHashCode for OtherClass. This should give me all the tools I need to compare these objects, and various tests comparing two singular instances of these objects so far checks out. However, I'm not sure how to approach this when they are in a List. I don't care about the list order. Given: Dim x As New List(Of OtherClass) From {New OtherClass("foo"), New OtherClass("bar"), New OtherClass("baz")} Dim y As New List(Of OtherClass) From {New OtherClass("baz"), New OtherClass("foo"), New OtherClass("bar")} Then (x = y).ToString should print out True. I need to compare the same (not distinct) set of objects in this list. The list shouldn't support dupes of OtherClass, but I'll have to figure out how to add that in later as an exception. Not interested in using LINQ. It looks nice, but in the few examples I've played with, adds a performance overhead in that bugs me. Loops are ugly, but they are fast :) A straight code answer is fine, but I'd like to understand the logic needed for such a comparison as well. I'm probably going to have to implement said logic more than a few times down the road.

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  • C++ Matrix class hierachy

    - by bpw1621
    Should a matrix software library have a root class (e.g., MatrixBase) from which more specialized (or more constrained) matrix classes (e.g., SparseMatrix, UpperTriangluarMatrix, etc.) derive? If so, should the derived classes be derived publicly/protectively/privately? If not, should they be composed with a implementation class encapsulating common functionality and be otherwise unrelated? Something else? I was having a conversation about this with a software developer colleague (I am not per se) who mentioned that it is a common programming design mistake to derive a more restricted class from a more general one (e.g., he used the example of how it was not a good idea to derive a Circle class from an Ellipse class as similar to the matrix design issue) even when it is true that a SparseMatrix "IS A" MatrixBase. The interface presented by both the base and derived classes should be the same for basic operations; for specialized operations, a derived class would have additional functionality that might not be possible to implement for an arbitrary MatrixBase object. For example, we can compute the cholesky decomposition only for a PositiveDefiniteMatrix class object; however, multiplication by a scalar should work the same way for both the base and derived classes. Also, even if the underlying data storage implementation differs the operator()(int,int) should work as expected for any type of matrix class. I have started looking at a few open-source matrix libraries and it appears like this is kind of a mixed bag (or maybe I'm looking at a mixed bag of libraries). I am planning on helping out with a refactoring of a math library where this has been a point of contention and I'd like to have opinions (that is unless there really is an objective right answer to this question) as to what design philosophy would be best and what are the pros and cons to any reasonable approach.

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  • Simple matrix example using C++ template class

    - by skyeagle
    I am trying to write a trivial Matrix class, using C++ templates in an attempt to brush up my C++, and also to explain something to a fellow coder. This is what I have som far: template class<T> class Matrix { public: Matrix(const unsigned int rows, const unsigned int cols); Matrix(const Matrix& m); Matrix& operator=(const Matrix& m); ~Matrix(); unsigned int getNumRows() const; unsigned int getNumCols() const; template <class T> T getCellValue(unsigned int row, unsigned col) const; template <class T> void setCellValue(unsigned int row, unsigned col, T value) const; private: // Note: intentionally NOT using smart pointers here ... T * m_values; }; template<class T> inline T Matrix::getCellValue(unsigned int row, unsigned col) const { } template<class T> inline void Matrix::setCellValue(unsigned int row, unsigned col, T value) { } I'm stuck on the ctor, since I need to allocate a new[] T, it seems like it needs to be a template method - however, I'm not sure I have come accross a templated ctor before. How can I implemnt the ctor?

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  • How to take a collection of bytes and pull typed values out of it?

    - by Pat
    Say I have a collection of bytes var bytes = new byte[] {0, 1, 2, 3, 4, 5, 6, 7}; and I want to pull out a defined value from the bytes as a managed type, e.g. a ushort. What is a simple way to define what types reside at what location in the collection and pull out those values? One (ugly) way is to use System.BitConverter and a Queue or byte[] with an index and simply iterate through, e.g.: int index = 0; ushort first = System.BitConverter.ToUint16(bytes, index); index += 2; // size of a ushort int second = System.BitConverter.ToInt32(bytes, index); index += 4; ... This method gets very, very tedious when you deal with a lot of these structures! I know that there is the System.Runtime.InteropServices.StructLayoutAttribute which allows me to define the locations of types inside a struct or class, but there doesn't seem to be a way to import the collection of bytes into that struct. If I could somehow overlay the struct on the collection of bytes and pull out the values, that would be ideal. E.g. Foo foo = (Foo)bytes; // doesn't work because I'd need to implement the implicit operator ushort first = foo.first; int second = foo.second; ... [StructLayout(LayoutKind.Explicit, Size=FOO_SIZE)] public struct Foo { [FieldOffset(0)] public ushort first; [FieldOffset(2)] public int second; } Any thoughts on how to achieve this?

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  • C++ Suppress Automatic Initialization and Destruction

    - by Travis G
    How does one suppress the automatic initialization and destruction of a type? While it is wonderful that T buffer[100] automatically initializes all the elements of buffer, and destroys them when they fall out of scope, this is not the behavior I want. #include <iostream> static int created = 0, destroyed = 0; struct S { S() { ++created; } ~S() { ++destroyed; } }; template <typename T, size_t KCount> class Array { private: T m_buffer[KCount]; public: Array() { // some way to suppress the automatic initialization of m_buffer } ~Array() { // some way to suppress the automatic destruction of m_buffer } }; int main() { { Array<S, 100> arr; } std::cout << "Created:\t" << created << std::endl; std::cout << "Destroyed:\t" << destroyed << std::endl; return 0; } The output of this program is: Created: 100 Destroyed: 100 I would like it to be: Created: 0 Destroyed: 0 My only idea is to make m_buffer some trivially constructed and destructed type like char and then rely on operator[] to wrap the pointer math for me, although this seems like a horribly hacked solution. Another solution would be to use malloc and free, but that gives a level of indirection that I do not want.

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  • useer degined Copy ctor, and copy-ctors further down the chain - compiler bug ? programers brainbug

    - by J.Colmsee
    Hi. i have a little problem, and I am not sure if it's a compiler bug, or stupidity on my side. I have this struct : struct BulletFXData { int time_next_fx_counter; int next_fx_steps; Particle particles[2];//this is the interesting one ParticleManager::ParticleId particle_id[2]; }; The member "Particle particles[2]" has a self-made kind of smart-ptr in it (resource-counted texture-class). this smart-pointer has a default constructor, that initializes to the ptr to 0 (but that is not important) I also have another struct, containing the BulletFXData struct : struct BulletFX { BulletFXData data; BulletFXRenderFunPtr render_fun_ptr; BulletFXUpdateFunPtr update_fun_ptr; BulletFXExplosionFunPtr explode_fun_ptr; BulletFXLifetimeOverFunPtr lifetime_over_fun_ptr; BulletFX( BulletFXData data, BulletFXRenderFunPtr render_fun_ptr, BulletFXUpdateFunPtr update_fun_ptr, BulletFXExplosionFunPtr explode_fun_ptr, BulletFXLifetimeOverFunPtr lifetime_over_fun_ptr) :data(data), render_fun_ptr(render_fun_ptr), update_fun_ptr(update_fun_ptr), explode_fun_ptr(explode_fun_ptr), lifetime_over_fun_ptr(lifetime_over_fun_ptr) { } /* //USER DEFINED copy-ctor. if it's defined things go crazy BulletFX(const BulletFX& rhs) :data(data),//this line of code seems to do a plain memory-copy without calling the right ctors render_fun_ptr(render_fun_ptr), update_fun_ptr(update_fun_ptr), explode_fun_ptr(explode_fun_ptr), lifetime_over_fun_ptr(lifetime_over_fun_ptr) { } */ }; If i use the user-defined copy-ctor my smart-pointer class goes crazy, and it seems that calling the CopyCtor / assignment operator aren't called as they should. So - does this all make sense ? it seems as if my own copy-ctor of struct BulletFX should do exactly what the compiler-generated would, but it seems to forget to call the right constructors down the chain. compiler bug ? me being stupid ? Sorry about the big code, some small example could have illustrated too. but often you guys ask for the real code, so well - here it is :D

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  • Help with this compile error

    - by Scott
    I just picked up an old project and I'm not sure what the following error could mean. g++ -o BufferedReader.o -c -g -Wall -std=c++0x -I/usr/include/xmms2 -Ijsoncpp/include/json/ -fopenmp -I/usr/include/ImageMagick -I/usr/include/xmms2 -I/usr/include/libvisual-0.4 -D_GNU_SOURCE=1 -D_REENTRANT -I/usr/include/SDL -DQT_CORE_LIB -DQT_GUI_LIB -DQT_SCRIPT_LIB -DQT_SHARED -I/usr/include/QtCore -I/usr/include/QtGui -I/usr/include/QtScript BufferedReader.cpp In file included from BufferedReader.cpp:23: /usr/include/string.h:36:42: error: missing binary operator before token "(" In file included from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/cwchar:47, from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/bits/postypes.h:42, from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/iosfwd:42, from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/ios:39, from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/istream:40, from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/sstream:39, from BufferedReader.cpp:24: At line 24 of BufferedReader.cpp is #include <string.h>. I've tried it with just <string> but get the same thing. Any clue? Here's the snippet of code from string.h /* Tell the caller that we provide correct C++ prototypes. */ #if defined __cplusplus && __GNUC_PREREQ (4, 4) //line 36 # define __CORRECT_ISO_CPP_STRING_H_PROTO #endif Does that mean __GNUC_PREREQ isn't defined?

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  • Parse files in directory/insert in database

    - by jakesankey
    Hey there, Here is my dillema... I have a directory full of .txt comma delimited files arranged as shown below. What I want to do is to import each of these into a SQL or SQLite database, appending each one below the last. (1 table)... I am open to C# or VB scripting and just not sure how to accomplish this. I want to only extract and import the data starting BELOW the 'Feat. Type,Feat. Name, etc' line. These are stored in a \mynetwork\directory\stats folder on my network drive. Ideally I will be able to add functionality that will make the software/script know not to re-add the file to the database once it has already done so as well. Any guidance or tips is appreciated! $$ SAMPLE= $$ FIXTURE=- $$ OPERATOR=- $$ INSPECTION PROCESS=CMM #4 $$ PROCESS OPERATION=- $$ PROCESS SEQUENCE=- $$ TRIAL=- Feat. Type,Feat. Name,Value,Actual,Nominal,Dev.,Tol-,Tol+,Out of Tol.,Comment Point,_FF_PLN_A_1,X,-17.445,-17.445,0.000,-999.000,999.000,, Point,_FF_PLN_A_1,Y,-195.502,-195.502,0.000,-999.000,999.000,, Point,_FF_PLN_A_1,Z,32.867,33.500,-0.633,-0.800,0.800,, Point,_FF_PLN_A_2,X,-73.908,-73.908,0.000,-999.000,999.000,, Point,_FF_PLN_A_2,Y,-157.957,-157.957,0.000,-999.000,999.000,, Point,_FF_PLN_A_2,Z,32.792,33.500,-0.708,-0.800,0.800,, Point,_FF_PLN_A_3,X,-100.180,-100.180,0.000,-999.000,999.000,, Point,_FF_PLN_A_3,Y,-142.797,-142.797,0.000,-999.000,999.000,, Point,_FF_PLN_A_3,Z,32.768,33.500,-0.732,-0.800,0.800,, Point,_FF_PLN_A_4,X,-160.945,-160.945,0.000,-999.000,999.000,, Point,_FF_PLN_A_4,Y,-112.705,-112.705,0.000,-999.000,999.000,, Point,_FF_PLN_A_4,Z,32.719,33.500,-0.781,-0.800,0.800,, Point,_FF_PLN_A_5,X,-158.096,-158.096,0.000,-999.000,999.000,, Point,_FF_PLN_A_5,Y,-73.821,-73.821,0.000,-999.000,999.000,, Point,_FF_PLN_A_5,Z,32.756,33.500,-0.744,-0.800,0.800,, Point,_FF_PLN_A_6,X,-195.670,-195.670,0.000,-999.000,999.000,, Point,_FF_PLN_A_6,Y,-17.375,-17.375,0.000,-999.000,999.000,, Point,_FF_PLN_A_6,Z,32.767,33.500,-0.733,-0.800,0.800,, Point,_FF_PLN_A_7,X,-173.759,-173.759,0.000,-999.000,999.000,, Point,_FF_PLN_A_7,Y,14.876,14.876,0.000,-999.000,999.000,,

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  • Passing functor and function pointers interchangeably using a templated method in C++

    - by metroxylon
    I currently have a templated class, with a templated method. Works great with functors, but having trouble compiling for functions. Foo.h template <typename T> class Foo { public: // Constructor, destructor, etc... template <typename Func> void bar(T x, Func f); }; template <typename T> template <typename Func> Foo::bar(T x, Func f) { /* some code here */ } Main.cpp #include "Foo.h" template <typename T> class Functor { public: Functor() {} void operator()(T x) { /* ... */ } private: /* some attributes here */ }; void Function(T x) { /* ... */ } int main() { Foo<int> foo; foo.bar(2, Functor); // No problem foo.bar(2, Function); // <unresolved overloaded function type> return 0; }

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  • Freeing ImageData when deleting a Canvas

    - by user578770
    I'm writing a XUL application using HTML Canvas to display Bitmap images. I'm generating ImageDatas and imporingt them in a canvas using the putImageData function : for(var pageIndex=0;pageIndex<100;pageIndex++){ this.img = imageDatas[pageIndex]; /* Create the Canvas element */ var imgCanvasTmp = document.createElementNS("http://www.w3.org/1999/xhtml",'html:canvas'); imgCanvasTmp.setAttribute('width', this.img.width); imgCanvasTmp.setAttribute('height', this.img.height); /* Import the image into the Canvas */ imgCanvasTmp.getContext('2d').putImageData(this.img, 0, 0); /* Use the Canvas into another part of the program (Commented out for testing) */ // this.displayCanvas(imgCanvasTmp,pageIndex); } The images are well imported but there seems to be a memory leak due to the putImageData function. When exiting the "for" loop, I would expect the memory allocated for the Canvas to be freed but, by executing the code without executing putImageData, I noticed that my program at the end use 100Mb less (my images are quite big). I came to the conclusion that the putImageData function prevent the garbage collector to free the allocated memory. Do you have any idea how I could force the garbage collector to free the memory? Is there any way to empty the Canvas? I already tried to delete the canvas using the delete operator or to use the clearRect function but it did nothing. I also tried to reuse the same canvas to display the image at each iteration but the amount of memory used did not changed, as if the image where imported without deleting the existing ones...

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  • show a particular div until content is loaded into another div from xml file in phonegap webservice

    - by Balu
    I am doing a webservice in phonegap.Here the application fetch values from a xml file in remote server when user search particular keyword and load the content to a div in my application.Here my problem is I want to show toast message like "loading..." or "progressing..." till the content is loaded into the div of application.I have created a toast message.But I dont know how to hide the toast message after the content is loaded since the time for fetching values from xml file is different for different keywords. The div to which content is loaded is <ul class="searchresults"></ul>.and my toast function is function toast(sMessage){ var container = $(document.createElement("div")); container.addClass("loading"); var message = $(document.createElement("div")); message.addClass("message"); message.text(sMessage); message.appendTo(container); container.appendTo(document.body); container.delay(150).fadeIn("slow", function() { if ($(".searchresults").html().length > 0) { //$(this).remove(); $(this).delay(500).fadeOut("slow", function() { $(this).remove(); }); } }); } Can anyone help me suggesting some ideas.Thanks in advance.

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  • which is better: a lying copy constructor or a non-standard one?

    - by PaulH
    I have a C++ class that contains a non-copyable handle. The class, however, must have a copy constructor. So, I've implemented one that transfers ownership of the handle to the new object (as below) class Foo { public: Foo() : h_( INVALID_HANDLE_VALUE ) { }; // transfer the handle to the new instance Foo( const Foo& other ) : h_( other.Detach() ) { }; ~Foo() { if( INVALID_HANDLE_VALUE != h_ ) CloseHandle( h_ ); }; // other interesting functions... private: /// disallow assignment const Foo& operator=( const Foo& ); HANDLE Detach() const { HANDLE h = h_; h_ = INVALID_HANDLE_VALUE; return h; }; /// a non-copyable handle mutable HANDLE h_; }; // class Foo My problem is that the standard copy constructor takes a const-reference and I'm modifying that reference. So, I'd like to know which is better (and why): a non-standard copy constructor: Foo( Foo& other ); a copy-constructor that 'lies': Foo( const Foo& other ); Thanks, PaulH

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  • C++ variable to const expression

    - by user1344784
    template <typename Real> class A{ }; template <typename Real> class B{ }; //... a few dozen more similar template classes class Computer{ public slots: void setFrom(int from){ from_ = from; } void setTo(int to){ to_ = to; } private: template <int F, int T> void compute(){ using boost::fusion::vector; using boost::fusion::at_c; vector<A<float>, B<float>, ...> v; at_c<from_>(v).operator()(at_c<to_>(v)); //error; needs to be const-expression. }; This question isn't about Qt, but there is a line of Qt code in my example. The setFrom() and setTo() are functions that are called based on user selection via the GUI widget. The root of my problem is that 'from' and 'to' are variables. In my compute member function I need to pick a type (A, B, etc.) based on the values of 'from' and 'to'. The only way I know how to do what I need to do is to use switch statements, but that's extremely tedious in my case and I would like to avoid. Is there anyway to convert the error line to a constant-expression?

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  • Only show link if conditional equals true

    - by Dave Morin
    I want the link to appear only when $data['block'] equals to 1, 3 or 4. Not if it equals to 2 or 5. <td style="font-size:18px;color:#f0cb01;"> <a href="kickcodes.php?id='.$data["block"].'">Reason Codes</a> </td> EDIT while ($data = mysql_fetch_array($query)) { echo ' <tr style="background-color:#576c11;"> <td style="font-size:18px; color:#f0cb01;">'.$data["keyword"].'</td> <td style="font-size:18px;color:#f0cb01;">'.$data["block"].'</td> <td style="font-size:18px;color:#f0cb01;">'.$data["phone"].'</td> <td style="font-size:18px;color:#f0cb01;">'.$data["Reason"].'</td> <td style="font-size:18px;color:#f0cb01;"><a href="kickcodes.php?id='.$data ["block"].'">Kickcodes</a></td>' echo '<td style="font-size:18px;color:#f0cb01;">'; if( $data['block'] == 1 || $data['block'] == 3 || $data['block'] == 4) { echo '<a href="kickcodes.php?id='.$data["block"].'">Reason Codes</a>'; } else { echo '<span>Reason Codes</span>'; // Or echo nothing } echo '</td>';

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  • Fluent NHibernate Mappings ClassMap<Entities>....

    - by Pandiya Chendur
    I was going through fluent hibernate getting started tutorial.... In my asp.net mvc web application i have created Entities and Mapping folder as they stated... I created an entity class and i tried to map it my mapping class using this, using System; using System.Collections.Generic; using System.Linq; using System.Web; using FluentNhibernateMVC.Entities; namespace FluentNhibernateMVC.Mappings { public class ClientMap : ClassMap<Client> { } } I cant able to find a ClassMap keyword in my autosuggest list why? This is my entity class using System; using System.Collections.Generic; using System.Linq; using System.Web; namespace FluentNhibernateMVC.Entities { public class Client { public int ClientId { get; set; } public string ClientName { get; set; } public string ClientMobNo { get; set; } public string ClientAddress { get; set; } public DateTime CreatedDate { get; set; } public byte IsDeleted { get; set; } public int CreatedBy { get; set; } } } I have added all references to my project...Am i missing some thing...

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  • how to emulate thread local storage at user space in C++ ?

    - by vprajan
    I am working on a mobile platform over Nucleus RTOS. It uses Nucleus Threading system but it doesn't have support for explicit thread local storage i.e, TlsAlloc, TlsSetValue, TlsGetValue, TlsFree APIs. The platform doesn't have user space pthreads as well. I found that __thread storage modifier is present in most of the C++ compilers. But i don't know how to make it work for my kind of usage. How does __thread keyword can be mapped with explicit thread local storage? I read many articles but nothing is so clear for giving me the following basic information will __thread variable different for each thread ? How to write to that and read from it ? does each thread has exactly one copy of the variable ? following is the pthread based implementation: pthread_key_t m_key; struct Data : Noncopyable { Data(T* value, void* owner) : value(value), owner(owner) {} int* value; }; inline ThreadSpecific() { int error = pthread_key_create(&m_key, destroy); if (error) CRASH(); } inline ~ThreadSpecific() { pthread_key_delete(m_key); // Does not invoke destructor functions. } inline T* get() { Data* data = static_cast<Data*>(pthread_getspecific(m_key)); return data ? data->value : 0; } inline void set(T* ptr) { ASSERT(!get()); pthread_setspecific(m_key, new Data(ptr, this)); } How to make the above code use __thread way to set & get specific value ? where/when does the create & delete happen? If this is not possible, how to write custom pthread_setspecific, pthread_getspecific kind of APIs. I tried using a C++ global map and index it uniquely for each thread and retrieved data from it. But it didn't work well.

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  • Circumvent c++ null-terminated string frustration

    - by ypnos
    I'm using boost::program_options and it suffers from the same as many other c++ libs, even std itself: It still uses C-style null-terminated strings, because nobody really likes the weak std::string. The method in question is: options_description_easy_init& operator()(const char* name, const value_semantic* s, const char* description); The typical use case is just fine: options.add_options() ("graphical", bool_switch(&isGraphical)->default_value(false), "Show any graphical output during runtime") However, I need the name of the option to be set dynamically. The reason is that in some cases I nead a custom prefix, which is added to the string by my function std::string key(const std::string& k): options.add_options() (key("graphical"), bool_switch(&isGraphical)->default_value(false), "Show any graphical output during runtime") This fails. I could now use c_str() on the std::string but that's evil -- I don't know how long program_options keeps the variable around and if my string is still alive when needed. I could also reserve memory in a buffer etc. and hand in that. The buffer is never freed and it sucks/is evil. Is there anything else I can do to circumvent the C-style string mess in this situation?

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  • How to iterate properly across a const set?

    - by Jared
    I'm working on a program that's supposed to represent a graph. My issue is in my printAdjacencyList function. Basically, I have a Graph ADT that has a member variable "nodes", which is a map of the nodes of that graph. Each Node has a set of Edge* to the edges it is connected to. I'm trying to iterate across each node in the graph and each edge of a node. void MyGraph::printAdjacencyList() { std::map<std::string, MyNode*>::iterator mit; std::set<MyEdge*>::iterator sit; for (mit = nodes.begin(); mit != nodes.end(); mit++ ) { std::cout << mit->first << ": {"; const std::set<MyEdge*> edges = mit->second->getEdges(); for (sit = edges.begin(); sit != edges.end(); sit++) { std::pair<MyNode*, MyNode*> edgeNodes = *sit->getEndpoints(); } } std::cout << " }" << std::endl; } getEdges is declared as: const std::set<MyEdge*>& getEdges() { return edges; }; and get Endpoints is declared as: const std::pair<MyNode*, MyNode*>& getEndpoints() { return nodes; }; The compiler error I'm getting is: MyGraph.cpp:63: error: request for member `getEndpoints' in `*(&sit)->std::_Rb_tree_const_iterator<_Tp>::operator-> [with _Tp = MyEdge*]()', which is of non-class type `MyEdge* const' MyGraph.cpp:63: warning: unused variable 'edgeNodes' I have figured out that this probably means I'm misusing const somewhere, but I can't figure out where for the life of me. Any information would be appreciated. Thanks!

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  • Understanding C++ pointers (when they point to a pointer)

    - by Stephano
    I think I understand references and pointers pretty well. Here is what I (think I) know: int i = 5; //i is a primitive type, the value is 5, i do not know the address. int *ptr; //a pointer to an int. i have no way if knowing the value yet. ptr = &i; //now i have an address for the value of i (called ptr) *ptr = 10; //go get the value stored at ptr and change it to 10 Please feel free to comment or correct these statements. Now I'm trying to make the jump to arrays of pointers. Here is what I do not know: char **char_ptrs = new char *[50]; Node **node_ptrs = new Node *[50]; My understanding is that I have 2 arrays of pointers, one set of pointers to chars and one to nodes. So if I wanted to set the values, I would do something like this: char_ptrs[0] = new char[20]; node_ptrs[0] = new Node; Now I have a pointer, in the 0 position of my array, in each respective array. Again, feel free to comment here if I'm confused. So, what does the ** operator do? Likewise, what is putting a single * next to the instantiation doing (*[50])? (what is that called exactly, instantiation?)

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  • Will this cause a problem with different runtimes with DLL?

    - by Milo
    My gui application supports polymorphic timed events so that means that the user calls new, and the gui calls delete. This can create a problem if the runtimes are incompatible. So I was told a proposed solution would be this: class base; class Deallocator { void operator()(base* ptr) { delete ptr; } } class base { public: base(Deallocator dealloc) { m_deleteFunc = dealloc; } ~base() { m_deleteFunc(this); } private: Deallocator m_deleteFunc; } int main { Deallocator deletefunc; base baseObj(deletefunc); } While this is a good solution, it does demand that the user create a Deallocator object which I do not want. I was however wondering if I provided a Deallocator to each derived class: eg class derived : public base { Deallocator dealloc; public: Derived() : base(dealloc); { } }; I think this still does not work though. The constraint is that: The addTimedEvent() function is part of the Widget class which is also in the dll, but it is instanced by the user. The other constraint is that some classes which derive from Widget call this function with their own timed event classes. Given that "he who called new must call delete" what could work given these constraints? Thanks

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  • Porting Perl to C++ `print "\x{2501}" x 12;`

    - by jippie
    I am porting a program from Perl to C++ as a learning objective. I arrived at a routine that draws a table with commands like the following: Perl: print "\x{2501}" x 12; And it draws 12 times a '?' ("box drawings heavy horizontal"). Now I figured out part of the problem already: Perl: \x{}, \x00 Hexadecimal escape sequence; C++: \unnnn To print a single Unicode character: C++: printf( "\u250f\n" ); But does C++ have a smart equivalent for the 'x' operator or would it come down to a for loop? UPDATE Let me include the full source code I am trying to compile with the proposed solution. The compiler does throw an errors: g++ -Wall -Werror project.cpp -o project project.cpp: In function ‘int main(int, char**)’: project.cpp:38:3: error: ‘string’ is not a member of ‘std’ project.cpp:38:15: error: expected ‘;’ before ‘s’ project.cpp:39:3: error: ‘cout’ is not a member of ‘std’ project.cpp:39:16: error: ‘s’ was not declared in this scope #include <stdlib.h> #include <stdint.h> #include <stdio.h> #include <string.h> int main ( int argc, char *argv[] ) { if ( argc != 2 ) { fprintf( stderr , "usage: %s matrix\n", argv[0] ); exit( 2 ); } else { //std::string s(12, "\u250f" ); std::string s(12, "u" ); std::cout << s; } }

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  • C# code simple console program not working

    - by Wast334
    I am trying to test some console ability in C#.. I can't get this code to work using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { Dim myMessage; myMessage = @"Hello World"; printf(@"%@", myMessage); return 0; } } } I am getting a bunch of compiler errors i am not sure what I am doing wrong..? Error 1 The type or namespace name 'Dim' could not be found (are you missing a using directive or an assembly reference?) C:\Documents and Settings\wstevens\Local Settings\Application Data\Temporary Projects\ConsoleApplication1\Program.cs 12 13 ConsoleApplication1 Error 2 The name 'printf' does not exist in the current context C:\Documents and Settings\wstevens\Local Settings\Application Data\Temporary Projects\ConsoleApplication1\Program.cs 14 13 ConsoleApplication1 Error 3 Since 'ConsoleApplication1.Program.Main(string[])' returns void, a return keyword must not be followed by an object expression C:\Documents and Settings\wstevens\Local Settings\Application Data\Temporary Projects\ConsoleApplication1\Program.cs 15 13 ConsoleApplication1

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  • Why it's can be compiled in GNU/C++, can't compiled in VC++2010 RTM?

    - by volnet
    #include #include #include #include "copy_of_auto_ptr.h" #ifdef _MSC_VER #pragma message("#include ") #include // http://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Pragmas.html#Diagnostic-Pragmas #endif /* case 1-4 is the requirement of the auto_ptr. which form http://ptgmedia.pearsoncmg.com/images/020163371X/autoptrupdate/auto_ptr_update.html */ /* case 1. (1) Direct-initialization, same type, e.g. */ std::auto_ptr source_int() { // return std::auto_ptr(new int(3)); std::auto_ptr tmp(new int(3)); return tmp; } /* case 2. (2) Copy-initialization, same type, e.g. */ void sink_int(std::auto_ptr p) { std::cout source_derived() { // return std::auto_ptr(new Derived()); std::auto_ptr tmp(new Derived()); return tmp; } /* case 4. (4) Copy-initialization, base-from-derived, e.g. */ void sink_base( std::auto_ptr p) { p-go(); } int main(void) { /* // auto_ptr */ // case 1. // auto_ptr std::auto_ptr p_int(source_int()); std::cout p_derived(source_derived()); p_derived-go(); // case 4. // auto_ptr sink_base(source_derived()); return 0; } In Eclipse(GNU C++.exe -v gcc version 3.4.5 (mingw-vista special r3)) it's two compile error: Description Resource Path Location Type initializing argument 1 of void sink_base(std::auto_ptr<Base>)' from result ofstd::auto_ptr<_Tp::operator std::auto_ptr<_Tp1() [with _Tp1 = Base, _Tp = Derived]' auto_ptr_ref_research.cpp auto_ptr_ref_research/auto_ptr_ref_research 190 C/C++ Problem Description Resource Path Location Type no matching function for call to `std::auto_ptr::auto_ptr(std::auto_ptr)' auto_ptr_ref_research.cpp auto_ptr_ref_research/auto_ptr_ref_research 190 C/C++ Problem But it's right in VS2010 RTM. Questions: Which compiler stand for the ISO C++ standard? The content of case 4 is the problem "auto_ptr & auto_ptr_ref want to resolve?"

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  • C#: at design time, how can I reliably determine the type of a variable that is declared using var?

    - by Cheeso
    I'm working on a completion (intellisense) facility for C# in emacs. The idea is, if a user types a fragment, then asks for completion via a particular keystroke combination, the completion facility will use .NET reflection to determine the possible completions. Doing this requires that the type of the thing being completed, be known. If it's a string, it has a set of known methods; if it's an Int32, it has a separate set of methods, and so on. Using semantic, a code lexer/parser package available in emacs, I can locate the variable declarations, and their types. Given that, it's straightforward to use reflection to get the methods and properties on the type, and then present the list of options to the user. The problem arrives when the code uses var in the declaration. How can I reliably determine the actual type used, when the variable is declared with the var keyword? Just to be clear, I don't need to determine it at runtime. I want to determine it at "Design time". So far the best idea I have is: extract the declaration statement, eg var foo = "a string value"; concatenate a statement foo.GetType(); dynamically compile the resulting C# fragment it into a new assembly load the assembly into a new AppDomain, run the framgment and get the return type. unload and discard the assembly This sounds awfully heavyweight, for each completion request in the editor. Any better ideas out there?

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  • What does an object look like in memory?

    - by NeilMonday
    This is probably a really dumb question, but I will ask anyway. I am curious what an object looks like in memory. Obviously it would have to have all of its member data in it. I assume that functions for an object would not be duplicated in memory (or maybe I am wrong?). It would seem wasteful to have 999 objects in memory all with the same function defined over and over. If there is only 1 function in memory for all 999 objects, then how does each function know who's member data to modify (I specifically want to know at the low level). Is there an object pointer that gets sent to the function behind the scenes? Perhaps it is different for every compiler? Also, how does the static keyword affect this? With static member data, I would think that all 999 objects would use the exact same memory location for their static member data. Where does this get stored? Static functions I guess would also just be one place in memory, and would not have to interact with instantiated objects, which I think I understand.

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