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  • C# Extend array type to overload operators

    - by Episodex
    I'd like to create my own class extending array of ints. Is that possible? What I need is array of ints that can be added by "+" operator to another array (each element added to each), and compared by "==", so it could (hopefully) be used as a key in dictionary. The thing is I don't want to implement whole IList interface to my new class, but only add those two operators to existing array class. I'm trying to do something like this: class MyArray : Array<int> But it's not working that way obviously ;). Sorry if I'm unclear but I'm searching solution for hours now... UPDATE: I tried something like this: class Zmienne : IEquatable<Zmienne> { public int[] x; public Zmienne(int ilosc) { x = new int[ilosc]; } public override bool Equals(object obj) { if (obj == null || GetType() != obj.GetType()) { return false; } return base.Equals((Zmienne)obj); } public bool Equals(Zmienne drugie) { if (x.Length != drugie.x.Length) return false; else { for (int i = 0; i < x.Length; i++) { if (x[i] != drugie.x[i]) return false; } } return true; } public override int GetHashCode() { int hash = x[0].GetHashCode(); for (int i = 1; i < x.Length; i++) hash = hash ^ x[i].GetHashCode(); return hash; } } Then use it like this: Zmienne tab1 = new Zmienne(2); Zmienne tab2 = new Zmienne(2); tab1.x[0] = 1; tab1.x[1] = 1; tab2.x[0] = 1; tab2.x[1] = 1; if (tab1 == tab2) Console.WriteLine("Works!"); And no effect. I'm not good with interfaces and overriding methods unfortunately :(. As for reason I'm trying to do it. I have some equations like: x1 + x2 = 0.45 x1 + x4 = 0.2 x2 + x4 = 0.11 There are a lot more of them, and I need to for example add first equation to second and search all others to find out if there is any that matches the combination of x'es resulting in that adding. Maybe I'm going in totally wrong direction?

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  • Why is Perl's smart-match operator considered broken?

    - by Sean McMillan
    I've seen a number of comments across the web Perl's smart-match operator is broken. I know it originally was part of Perl 6, then was implemented in Perl 5.10 off of an old version of the spec, and was then corrected in 5.10.1 to match the current Perl 6 spec. Is the problem fixed in 5.10.1+, or are there other problems with the smart-match operator that make it troublesome in practice? What are the problems? Is there a yet-more-updated version (Perl 6, perhaps) that fixes the problems?

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  • Undocumented Gmail Search Operator Ferrets Out Large Email Attachments

    - by Jason Fitzpatrick
    If you’re looking for a way to quickly find large email attachments in your Gmail account, this undocumented search operator makes it simple to zero in on the hulking attachments hiding out in your inbox. To use the search operator simply plug in “size:” and some value to narrow your search to only emails that size or larger. In the screenshot above we searched for “size:20000000″ to search for files roughly 20MB or larger (if you want to be extremely precise, a true 20MB search would be “size:20971520″). If you’re looking to clean up your Gmail account this is a nearly zero-effort way to find the biggest space hogs–in our case, we found an email packed with massive PDF files from a 5 year old project that we were more than happy to purge. Finding Large Attachments in Google Mail/Gmail [via gHacks] 6 Ways Windows 8 Is More Secure Than Windows 7 HTG Explains: Why It’s Good That Your Computer’s RAM Is Full 10 Awesome Improvements For Desktop Users in Windows 8

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  • Why would one overload the && and & operator?

    - by acidzombie24
    The same question goes for | and ||. Why would one overload or 'use' the & and && operator? The only use i thought of are Bitwise Ands for int base types (but not float/decimals) using & logical short circuit for bools/functions that return bool. Using the && operator usually. I cant think of any classes that use those operators. Absolutely none. I know a class might support + (and not '-') which combine two strings together. I seen an object such as datetime overload '-' so two dates can be subtracted to make a timespan (obviously you cant add two dates) but i never seen &, &&, | and || used. Does anyone know of a use? In any language?

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  • Template inheritence c++

    - by Chris Condy
    I have made a template singleton class, I have also made a data structure that is templated. My question is; how do I make my templated data structure inherit from a singleton so you can only have one float type of this structure? I have tested both seperate and have found no problems. Code provided under... (That is the problem) template <class Type> class AbstractRManagers : public Singleton<AbstractRManagers<Type> > The problem is the code above doesn't work I get alot of errors. I cant get it to no matter what I do template a templated singleton class... I was asking for maybe advice or maybe if the code above is incorrect guidence? #ifndef SINGLETON_H #define SINGLETON_H template <class Type> class Singleton { public: virtual ~Singleton(); Singleton(); static Type* m_instance; }; template <class Type> Type* Singleton<Type>::m_instance = 0; #include "Singleton.cpp" #endif #ifndef SINGLETON_CPP #define SINGLETON_CPP #include "Singleton.h" template <class Type> Singleton<Type>::Singleton() { } template <class Type> Singleton<Type>::~Singleton() { } template <class Type> Type* Singleton<Type>::getInstance() { if(m_instance==nullptr) { m_instance = new Type; } return m_instance; } #endif #ifndef ABSTRACTRMANAGERS_H #define ABSTRACTRMANAGERS_H #include <vector> #include <map> #include <stack> #include "Singleton.h" template <class Type> class AbstractRManagers : public Singleton<AbstractRManagers<Type> > { public: virtual ~AbstractRManagers(); int insert(Type* type, std::string name); Type* remove(int i); Type* remove(std::string name); Type* get(int i); Type* getS(std::string name); int get(std::string name); int get(Type* i); bool check(std::string name); int resourceSize(); protected: private: std::vector<Type*> m_resources; std::map<std::string,int> m_map; std::stack<int> m_freePos; }; #include "AbstractRManagers.cpp" #endif #ifndef ABSTRACTRMANAGERS_CPP #define ABSTRACTRMANAGERS_CPP #include "AbstractRManagers.h" template <class Type> int AbstractRManagers<Type>::insert(Type* type, std::string name) { int i=0; if(!check(name)) { if(m_freePos.empty()) { m_resources.push_back(type); i = m_resources.size()-1; m_map[name] = i; } else { i = m_freePos.top(); m_freePos.pop(); m_resources[i] = type; m_map[name] = i; } } else i = -1; return i; } template <class Type> int AbstractRManagers<Type>::resourceSize() { return m_resources.size(); } template <class Type> bool AbstractRManagers<Type>::check(std::string name) { std::map<std::string,int>::iterator it; it = m_map.find(name); if(it==m_map.end()) return false; return true; } template <class Type> Type* AbstractRManagers<Type>::remove(std::string name) { Type* temp = m_resources[m_map[name]]; if(temp!=NULL) { std::map<std::string,int>::iterator it; it = m_map[name]; m_resources[m_map[name]] = NULL; m_freePos.push(m_map[name]); delete (*it).second; delete (*it).first; return temp; } return NULL; } template <class Type> Type* AbstractRManagers<Type>::remove(int i) { if((i < m_resources.size())&&(i > 0)) { Type* temp = m_resources[i]; m_resources[i] = NULL; m_freePos.push(i); std::map<std::string,int>::iterator it; for(it=m_map.begin();it!=m_map.end();it++) { if((*it).second == i) { delete (*it).second; delete (*it).first; return temp; } } return temp; } return NULL; } template <class Type> int AbstractRManagers<Type>::get(Type* i) { for(int i2=0;i2<m_resources.size();i2++) { if(i == m_resources[i2]) { return i2; } } return -1; } template <class Type> Type* AbstractRManagers<Type>::get(int i) { if((i < m_resources.size())&&(i >= 0)) { return m_resources[i]; } return NULL; } template <class Type> Type* AbstractRManagers<Type>::getS(std::string name) { return m_resources[m_map[name]]; } template <class Type> int AbstractRManagers<Type>::get(std::string name) { return m_map[name]; } template <class Type> AbstractRManagers<Type>::~AbstractRManagers() { } #endif #include "AbstractRManagers.h" struct b { float x; }; int main() { b* a = new b(); AbstractRManagers<b>::getInstance()->insert(a,"a"); return 0; } This program produces next errors when compiled : 1> main.cpp 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::stack<_Ty,_Container> &,const std::stack<_Ty,_Container> &)' : could not deduce template argument for 'const std::stack<_Ty,_Container> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\stack(166) : see declaration of 'std::operator <' 1> c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(124) : while compiling class template member function 'bool std::less<_Ty>::operator ()(const _Ty &,const _Ty &) const' 1> with 1> [ 1> _Ty=std::string 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\map(71) : see reference to class template instantiation 'std::less<_Ty>' being compiled 1> with 1> [ 1> _Ty=std::string 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(451) : see reference to class template instantiation 'std::_Tmap_traits<_Kty,_Ty,_Pr,_Alloc,_Mfl>' being compiled 1> with 1> [ 1> _Kty=std::string, 1> _Ty=int, 1> _Pr=std::less<std::string>, 1> _Alloc=std::allocator<std::pair<const std::string,int>>, 1> _Mfl=false 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(520) : see reference to class template instantiation 'std::_Tree_nod<_Traits>' being compiled 1> with 1> [ 1> _Traits=std::_Tmap_traits<std::string,int,std::less<std::string>,std::allocator<std::pair<const std::string,int>>,false> 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(659) : see reference to class template instantiation 'std::_Tree_val<_Traits>' being compiled 1> with 1> [ 1> _Traits=std::_Tmap_traits<std::string,int,std::less<std::string>,std::allocator<std::pair<const std::string,int>>,false> 1> ] 1> c:\program files\microsoft visual studio 10.0\vc\include\map(81) : see reference to class template instantiation 'std::_Tree<_Traits>' being compiled 1> with 1> [ 1> _Traits=std::_Tmap_traits<std::string,int,std::less<std::string>,std::allocator<std::pair<const std::string,int>>,false> 1> ] 1> c:\users\chris\desktop\311\ideas\idea1\idea1\abstractrmanagers.h(28) : see reference to class template instantiation 'std::map<_Kty,_Ty>' being compiled 1> with 1> [ 1> _Kty=std::string, 1> _Ty=int 1> ] 1> c:\users\chris\desktop\311\ideas\idea1\idea1\abstractrmanagers.h(30) : see reference to class template instantiation 'AbstractRManagers<Type>' being compiled 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::stack<_Ty,_Container> &,const std::stack<_Ty,_Container> &)' : could not deduce template argument for 'const std::stack<_Ty,_Container> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\stack(166) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::stack<_Ty,_Container> &,const std::stack<_Ty,_Container> &)' : could not deduce template argument for 'const std::stack<_Ty,_Container> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\stack(166) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::deque<_Ty,_Alloc> &,const std::deque<_Ty,_Alloc> &)' : could not deduce template argument for 'const std::deque<_Ty,_Alloc> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\deque(1725) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::deque<_Ty,_Alloc> &,const std::deque<_Ty,_Alloc> &)' : could not deduce template argument for 'const std::deque<_Ty,_Alloc> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\deque(1725) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::deque<_Ty,_Alloc> &,const std::deque<_Ty,_Alloc> &)' : could not deduce template argument for 'const std::deque<_Ty,_Alloc> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\deque(1725) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Tree<_Traits> &,const std::_Tree<_Traits> &)' : could not deduce template argument for 'const std::_Tree<_Traits> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(1885) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Tree<_Traits> &,const std::_Tree<_Traits> &)' : could not deduce template argument for 'const std::_Tree<_Traits> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(1885) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Tree<_Traits> &,const std::_Tree<_Traits> &)' : could not deduce template argument for 'const std::_Tree<_Traits> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xtree(1885) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::vector<_Ty,_Ax> &,const std::vector<_Ty,_Ax> &)' : could not deduce template argument for 'const std::vector<_Ty,_Ax> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\vector(1502) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::vector<_Ty,_Ax> &,const std::vector<_Ty,_Ax> &)' : could not deduce template argument for 'const std::vector<_Ty,_Ax> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\vector(1502) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::vector<_Ty,_Ax> &,const std::vector<_Ty,_Ax> &)' : could not deduce template argument for 'const std::vector<_Ty,_Ax> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\vector(1502) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::unique_ptr<_Ty,_Dx> &,const std::unique_ptr<_Ty2,_Dx2> &)' : could not deduce template argument for 'const std::unique_ptr<_Ty,_Dx> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\memory(2582) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::unique_ptr<_Ty,_Dx> &,const std::unique_ptr<_Ty2,_Dx2> &)' : could not deduce template argument for 'const std::unique_ptr<_Ty,_Dx> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\memory(2582) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::unique_ptr<_Ty,_Dx> &,const std::unique_ptr<_Ty2,_Dx2> &)' : could not deduce template argument for 'const std::unique_ptr<_Ty,_Dx> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\memory(2582) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::reverse_iterator<_RanIt> &,const std::reverse_iterator<_RanIt2> &)' : could not deduce template argument for 'const std::reverse_iterator<_RanIt> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1356) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::reverse_iterator<_RanIt> &,const std::reverse_iterator<_RanIt2> &)' : could not deduce template argument for 'const std::reverse_iterator<_RanIt> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1356) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::reverse_iterator<_RanIt> &,const std::reverse_iterator<_RanIt2> &)' : could not deduce template argument for 'const std::reverse_iterator<_RanIt> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1356) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Revranit<_RanIt,_Base> &,const std::_Revranit<_RanIt2,_Base2> &)' : could not deduce template argument for 'const std::_Revranit<_RanIt,_Base> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1179) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Revranit<_RanIt,_Base> &,const std::_Revranit<_RanIt2,_Base2> &)' : could not deduce template argument for 'const std::_Revranit<_RanIt,_Base> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1179) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::_Revranit<_RanIt,_Base> &,const std::_Revranit<_RanIt2,_Base2> &)' : could not deduce template argument for 'const std::_Revranit<_RanIt,_Base> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\xutility(1179) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::pair<_Ty1,_Ty2> &,const std::pair<_Ty1,_Ty2> &)' : could not deduce template argument for 'const std::pair<_Ty1,_Ty2> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\utility(318) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::pair<_Ty1,_Ty2> &,const std::pair<_Ty1,_Ty2> &)' : could not deduce template argument for 'const std::pair<_Ty1,_Ty2> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\utility(318) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2784: 'bool std::operator <(const std::pair<_Ty1,_Ty2> &,const std::pair<_Ty1,_Ty2> &)' : could not deduce template argument for 'const std::pair<_Ty1,_Ty2> &' from 'const std::string' 1> c:\program files\microsoft visual studio 10.0\vc\include\utility(318) : see declaration of 'std::operator <' 1>c:\program files\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2676: binary '<' : 'const std::string' does not define this operator or a conversion to a type acceptable to the predefined operator ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

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  • Boot-repair commands not found in PATH or not executable

    - by Bram Meerten
    I recently had problems with my ubuntu partition (after the battery died), I managed to fix them by running ubuntu from usb and run gparted. It worked I can access my files on the partition by running ubuntu from usb. But when I restart the computer, after selecting ubuntu in Grub, I get a black screen with a white underscore. I googled the problem, and tried to solve it by setting nomodeset, but it didn't work. Next I wanted to try to fix Grub using boot-repair, I clicked on 'Recommended repair', it tells me to type the following commands in the terminal: sudo chroot "/mnt/boot-sav/sda5" apt-get install -fy sudo chroot "/mnt/boot-sav/sda5" dpkg --configure -a sudo chroot "/mnt/boot-sav/sda5" apt-get purge -y --force-yes grub-common But when running the second command, I get this error: dpkg: warning: 'sh' not found in PATH or not executable. dpkg: warning: 'rm' not found in PATH or not executable. dpkg: warning: 'tar' not found in PATH or not executable. dpkg: error: 3 expected programs not found in PATH or not executable. Note: root's PATH should usually contain /usr/local/sbin, /usr/sbin and /sbin. I didn't edit /etc/environment (or any other files), this is what it looks like: PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games" RUNNING_UNDER_GDM="yes" I have no idea how to fix this. I'm running dualboot Ubuntu 12.04 and Windows 7, Windows boots fine.

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  • When I overload the assignment operator for my simple class array, I get the wrong answer I espect

    - by user299648
    //output is "01234 00000" but the output should be or what I want it to be is // "01234 01234" because of the assignment overloaded operator #include <iostream> using namespace std; class IntArray { public: IntArray() : size(10), used(0) { a= new int[10]; } IntArray(int s) : size(s), used(0) { a= new int[s]; } int& operator[]( int index ); IntArray& operator =( const IntArray& rightside ); ~IntArray() { delete [] a; } private: int *a; int size; int used;//for array position }; int main() { IntArray copy; if( 2>1) { IntArray arr(5); for( int k=0; k<5; k++) arr[k]=k; copy = arr; for( int j=0; j<5; j++) cout<<arr[j]; } cout<<" "; for( int j=0; j<5; j++) cout<<copy[j]; return 0; } int& IntArray::operator[]( int index ) { if( index >= size ) cout<<"ilegal index in IntArray"<<endl; return a[index]; } IntArray& IntArray::operator =( const IntArray& rightside ) { if( size != rightside.size )//also checks if on both side same object { delete [] a; a= new int[rightside.size]; } size=rightside.size; used=rightside.used; for( int i = 0; i < used; i++ ) a[i]=rightside.a[i]; return *this; }

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  • Assigning a vector of one type to a vector of another type

    - by deworde
    Hi, I have an "Event" class. Due to the way dates are handled, we need to wrap this class in a "UIEvent" class, which holds the Event, and the date of the Event in another format. What is the best way of allowing conversion from Event to UIEvent and back? I thought overloading the assignment or copy constructor of UIEvent to accept Events (and vice versa)might be best.

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  • == and === operators in php

    - by Lizard
    Lets say I have a variable that will always be a string. Now take the code below: if($myVar === "teststring") Note $myVar will always be a string, so my questions is Which is quicker/best, using === (Indentity) or the == (Equality)?

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  • Maximize, minimize and close buttons are either not present or not working in Lubuntu

    - by jimirings
    As the title indicates, the maximize, minimize, and close buttons are either not present or not working on my Lubuntu desktop. In fact, it only seems to be Google Chrome that displays the buttons at all, and only the close button works in Chrome, maximize and minimize don't do anything. When I use regular Ubuntu, they're all there just fine but not on Lubuntu. This all seemed to occur after I hooked my netbook up to an external monitor while using Lubuntu. Not sure if that had anything to do with it or not, but it seemed too big of a coincidence to not mention. Any ideas what the cause and a fix might be? Thanks in advance.

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  • Templated << friend not working when in interrelationship with other templated union types

    - by Dwight
    While working on my basic vector library, I've been trying to use a nice syntax for swizzle-based printing. The problem occurs when attempting to print a swizzle of a different dimension than the vector in question. In GCC 4.0, I originally had the friend << overloaded functions (with a body, even though it duplicated code) for every dimension in each vector, which caused the code to work, even if the non-native dimension code never actually was called. This failed in GCC 4.2. I recently realized (silly me) that only the function declaration was needed, not the body of the code, so I did that. Now I get the same warning on both GCC 4.0 and 4.2: LINE 50 warning: friend declaration 'std::ostream& operator<<(std::ostream&, const VECTOR3<TYPE>&)' declares a non-template function Plus the five identical warnings more for the other function declarations. The below example code shows off exactly what's going on and has all code necessary to reproduce the problem. #include <iostream> // cout, endl #include <sstream> // ostream, ostringstream, string using std::cout; using std::endl; using std::string; using std::ostream; // Predefines template <typename TYPE> union VECTOR2; template <typename TYPE> union VECTOR3; template <typename TYPE> union VECTOR4; typedef VECTOR2<float> vec2; typedef VECTOR3<float> vec3; typedef VECTOR4<float> vec4; template <typename TYPE> union VECTOR2 { private: struct { TYPE x, y; } v; struct s1 { protected: TYPE x, y; }; struct s2 { protected: TYPE x, y; }; struct s3 { protected: TYPE x, y; }; struct s4 { protected: TYPE x, y; }; struct X : s1 { operator TYPE() const { return s1::x; } }; struct XX : s2 { operator VECTOR2<TYPE>() const { return VECTOR2<TYPE>(s2::x, s2::x); } }; struct XXX : s3 { operator VECTOR3<TYPE>() const { return VECTOR3<TYPE>(s3::x, s3::x, s3::x); } }; struct XXXX : s4 { operator VECTOR4<TYPE>() const { return VECTOR4<TYPE>(s4::x, s4::x, s4::x, s4::x); } }; public: VECTOR2() {} VECTOR2(const TYPE& x, const TYPE& y) { v.x = x; v.y = y; } X x; XX xx; XXX xxx; XXXX xxxx; // Overload for cout friend ostream& operator<<(ostream& os, const VECTOR2<TYPE>& toString) { os << "(" << toString.v.x << ", " << toString.v.y << ")"; return os; } friend ostream& operator<<(ostream& os, const VECTOR3<TYPE>& toString); friend ostream& operator<<(ostream& os, const VECTOR4<TYPE>& toString); }; template <typename TYPE> union VECTOR3 { private: struct { TYPE x, y, z; } v; struct s1 { protected: TYPE x, y, z; }; struct s2 { protected: TYPE x, y, z; }; struct s3 { protected: TYPE x, y, z; }; struct s4 { protected: TYPE x, y, z; }; struct X : s1 { operator TYPE() const { return s1::x; } }; struct XX : s2 { operator VECTOR2<TYPE>() const { return VECTOR2<TYPE>(s2::x, s2::x); } }; struct XXX : s3 { operator VECTOR3<TYPE>() const { return VECTOR3<TYPE>(s3::x, s3::x, s3::x); } }; struct XXXX : s4 { operator VECTOR4<TYPE>() const { return VECTOR4<TYPE>(s4::x, s4::x, s4::x, s4::x); } }; public: VECTOR3() {} VECTOR3(const TYPE& x, const TYPE& y, const TYPE& z) { v.x = x; v.y = y; v.z = z; } X x; XX xx; XXX xxx; XXXX xxxx; // Overload for cout friend ostream& operator<<(ostream& os, const VECTOR3<TYPE>& toString) { os << "(" << toString.v.x << ", " << toString.v.y << ", " << toString.v.z << ")"; return os; } friend ostream& operator<<(ostream& os, const VECTOR2<TYPE>& toString); friend ostream& operator<<(ostream& os, const VECTOR4<TYPE>& toString); }; template <typename TYPE> union VECTOR4 { private: struct { TYPE x, y, z, w; } v; struct s1 { protected: TYPE x, y, z, w; }; struct s2 { protected: TYPE x, y, z, w; }; struct s3 { protected: TYPE x, y, z, w; }; struct s4 { protected: TYPE x, y, z, w; }; struct X : s1 { operator TYPE() const { return s1::x; } }; struct XX : s2 { operator VECTOR2<TYPE>() const { return VECTOR2<TYPE>(s2::x, s2::x); } }; struct XXX : s3 { operator VECTOR3<TYPE>() const { return VECTOR3<TYPE>(s3::x, s3::x, s3::x); } }; struct XXXX : s4 { operator VECTOR4<TYPE>() const { return VECTOR4<TYPE>(s4::x, s4::x, s4::x, s4::x); } }; public: VECTOR4() {} VECTOR4(const TYPE& x, const TYPE& y, const TYPE& z, const TYPE& w) { v.x = x; v.y = y; v.z = z; v.w = w; } X x; XX xx; XXX xxx; XXXX xxxx; // Overload for cout friend ostream& operator<<(ostream& os, const VECTOR4& toString) { os << "(" << toString.v.x << ", " << toString.v.y << ", " << toString.v.z << ", " << toString.v.w << ")"; return os; } friend ostream& operator<<(ostream& os, const VECTOR2<TYPE>& toString); friend ostream& operator<<(ostream& os, const VECTOR3<TYPE>& toString); }; // Test code int main (int argc, char * const argv[]) { vec2 my2dVector(1, 2); cout << my2dVector.x << endl; cout << my2dVector.xx << endl; cout << my2dVector.xxx << endl; cout << my2dVector.xxxx << endl; vec3 my3dVector(3, 4, 5); cout << my3dVector.x << endl; cout << my3dVector.xx << endl; cout << my3dVector.xxx << endl; cout << my3dVector.xxxx << endl; vec4 my4dVector(6, 7, 8, 9); cout << my4dVector.x << endl; cout << my4dVector.xx << endl; cout << my4dVector.xxx << endl; cout << my4dVector.xxxx << endl; return 0; } The code WORKS and produces the correct output, but I prefer warning free code whenever possible. I followed the advice the compiler gave me (summarized here and described by forums and StackOverflow as the answer to this warning) and added the two things that supposedly tells the compiler what's going on. That is, I added the function definitions as non-friends after the predefinitions of the templated unions: template <typename TYPE> ostream& operator<<(ostream& os, const VECTOR2<TYPE>& toString); template <typename TYPE> ostream& operator<<(ostream& os, const VECTOR3<TYPE>& toString); template <typename TYPE> ostream& operator<<(ostream& os, const VECTOR4<TYPE>& toString); And, to each friend function that causes the issue, I added the <> after the function name, such as for VECTOR2's case: friend ostream& operator<< <> (ostream& os, const VECTOR3<TYPE>& toString); friend ostream& operator<< <> (ostream& os, const VECTOR4<TYPE>& toString); However, doing so leads to errors, such as: LINE 139: error: no match for 'operator<<' in 'std::cout << my2dVector.VECTOR2<float>::xxx' What's going on? Is it something related to how these templated union class-like structures are interrelated, or is it due to the unions themselves? Update After rethinking the issues involved and listening to the various suggestions of Potatoswatter, I found the final solution. Unlike just about every single cout overload example on the internet, I don't need access to the private member information, but can use the public interface to do what I wish. So, I make a non-friend overload functions that are inline for the swizzle parts that call the real friend overload functions. This bypasses the issues the compiler has with templated friend functions. I've added to the latest version of my project. It now works on both versions of GCC I tried with no warnings. The code in question looks like this: template <typename SWIZZLE> inline typename EnableIf< Is2D< typename SWIZZLE::PARENT >, ostream >::type& operator<<(ostream& os, const SWIZZLE& printVector) { os << (typename SWIZZLE::PARENT(printVector)); return os; } template <typename SWIZZLE> inline typename EnableIf< Is3D< typename SWIZZLE::PARENT >, ostream >::type& operator<<(ostream& os, const SWIZZLE& printVector) { os << (typename SWIZZLE::PARENT(printVector)); return os; } template <typename SWIZZLE> inline typename EnableIf< Is4D< typename SWIZZLE::PARENT >, ostream >::type& operator<<(ostream& os, const SWIZZLE& printVector) { os << (typename SWIZZLE::PARENT(printVector)); return os; }

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  • Is calling of overload operator-> resolved at compile time?

    - by Brent
    when I tried to compile the code: (note: func and func2 is not typo) struct S { void func2() {} }; class O { public: inline S* operator->() const; private: S* ses; }; inline S* O::operator->() const { return ses; } int main() { O object; object->func(); return 0; } there is a compile error reported: D:\code>g++ operatorp.cpp -S -o operatorp.exe operatorp.cpp: In function `int main()': operatorp.cpp:27: error: 'struct S' has no member named 'func' it seems that invoke the overloaded function of "operator-" is done during compile time? I'd added "-S" option for compile only.

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  • Is it possible to supply template parameters when calling operator()?

    - by Paul
    I'd like to use a template operator() but am not sure if it's possible. Here is a simple test case that won't compile. Is there something wrong with my syntax, or is this simply not possible? struct A { template<typename T> void f() { } template<typename T> void operator()() { } }; int main() { A a; a.f<int>(); // This compiles. a.operator()<int>(); // This compiles. a<int>(); // This won't compile. return 0; }

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  • Showplan Operator of the Week - Compute Scalar

    The third part of Fabiano's mission to describe the major Showplan Operators used by SQL Server's Query Optimiser continues with the 'Compute Scalar' operator. Fabiano shows how a tweak to SQL to avoid a 'Compute Scalar' step can improve its performance.

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  • Showplan Operator of the Week - Lazy Spool

    Continuing to illuminate the depths of SQL Server's Query Optimizer, Fabiano shines a light on the sixth major Showplan Operator on his list: the Lazy Spool. What does the Lazy Spool do that's so special, how does the Query Optimizer use it, and why is it so Lazy? Fabiano explains all...

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  • Showplan Operator of the Week - Merge Interval

    When Fabiano agreed to undertake the epic task of describing each showplan operator, none of us quite predicted the interesting ways that the series helps to understand how the query optimizer works. With the Merge Interval, Fabiano comes up with some insights about the way that the Query optimizer handles overlapping ranges efficiently. Free trial of SQL Backup™“SQL Backup was able to cut down my backup time significantly AND achieved a 90% compression at the same time!” Joe Cheng. Download a free trial now.

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  • Showplan Operator of the Week - Concatenation

    Fabiano continues in his mission to describe, one week at a time, all the major Showplan Operators used by SQL Server's Query Optimiser to build the Query Plan. This week he gets the Concatenation operator ....Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • C# Algorithms for * Operator

    - by Harsha
    I was reading up on Algorithms and came across the Karatsuba multiplication algorithm and a little wiki-ing led to the Schonhage-Strassen and Furer algorithms for multiplication. I was wondering what algorithms are used on the * operator in C#? While multiplying a pair of integers or doubles, does it use a combination of algorithms with some kind of strategy based on the size of the numbers? How could I find out the implementation details for C#?

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  • ShowPlan Operator of the Week - Merge Join

    Did you ever wonder how and why your indexes affect the performances of joins? Once you've read Fabiano Amorim's unforgettable explanation, you'll learn to love the MERGE operator, and plan your indexes so as to allow the Query Optimiser to use it. Free trial of SQL Backup™“SQL Backup was able to cut down my backup time significantly AND achieved a 90% compression at the same time!” Joe Cheng. Download a free trial now.

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  • Call the cast operator of template base class within the derived class

    - by yoni
    I have a template class, called Cell, here the definition: template <class T> class OneCell { ..... } I have a cast operator from Cell to T, here virtual operator const T() const { ..... } Now i have derived class, called DCell, here template <class T> class DCell : public Cell<T> { ..... } I need to override the Cell's cast operator (insert a little if), but after I need to call the Cell's cast operator. In other methods it's should be something like virtual operator const T() const { if (...) { return Cell<T>::operator const T; } else throw ... } but i got a compiler error error: argument of type 'const int (Cell::)()const' does not match 'const int' What can I do? Thank you, and sorry about my poor English.

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  • What are the best practices for implementing the == operator for a class in C#?

    - by remio
    While implementing an == operator, I have the feeling that I am missing some essential points. Hence, I am searching some best practices around that. Here are some related questions I am thinking about: How to cleanly handle the reference comparison? Should it be implemented through a IEquatable<T>-like interface? Or overriding object.Equals? And what about the != operator? (this list might not be exhaustive).

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