Category : reference

Hi i am reading about expression in C++ and across the statement Statement 0.0 Each expression has some non-reference type The quoted statement is from en.cppreference.com/w/cpp/language/value_category. Check line 2 at the top of the page. Now i took some examples to understand what this means. For example: int i = 100; // this expression has ..

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To optimize, I am returning objects by reference since, I do not need to change them, and they can be really large objects. But what if, in case, the underlying object is not present? Example, consider below code… map<string,map<string,int> > mMap; map<string,int> & GetReference(string x){ if(mMap.find(x)==mMap.end()){ }else{ return mMap[x]; } } int main() { mMap["abc"].insert(make_pair("cat",1)); ..

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I want to use the result of TranslatePolygon in //*, storing its returned value into another variable in the function TranslateConformedReferenceElement. In code I get the following warning at //** "warning: reference to stack memory associated with local variable ‘translatedPolygon’ returned" I know The referred value dies when the function call is over, but still ..

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I see some code examples where the type used to instantiate the std::declval template function is specified as a reference type rather than just a type, as in: std::declval<T &>() as opposed to: std::declval<T>() where T is some type. I am missing the subtlety why the reference notation might be chosen overe the plain type. ..

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I don’t know how to return reference to 3d vector element. Here is definition in class: vector<vector<vector<bool>>> bitmap; Initialization in constructor: bitmap(x, vector<vector<bool>>(y, vector<bool>(z, 0))) {}; I have to overload operator (), which return reference to bitmap[x][y][z]. bool& BitmapaExt::operator()(unsigned x, unsigned y, unsigned z) { return … ; } I tried &bitmap[x][y][z], error : C ..

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