Advertisements this line of code is wrong and won’t compile but i am wondering if it can be fixed. #include <iostream> template <typename T> auto getValue() { std::cout << "Enter an integral value: "; T value{}; std::cin >> value; // I would do input handing later return value; } int main() { auto value1{getValue()}; std::cout… Read More Can I use template or auto keyword in cpp to create a variable that i can use with std:: cin to get a value from user?

Advertisements MRE: std::vector<std::string> someFunction() { auto vec; return vec; } What’s stopping "auto" from inferring the type of vec as std::vector<std::string>? >Solution : From your question, it appears that you believe that since the compiler knows the return type, it should be able to deduce that the variable being returned must be of that return… Read More Why can't auto infer the type when the return type is specified?

Advertisements Consider this code template <typename OUT> auto fun(const int& x) { return [&](function<OUT(int)> fout) -> decltype(fout(x)) {return fout(x);}; } calling function auto w = fun(23)([](const auto& x) {return x*2;}); The function fun when called cannot deduce the return type as above code fails compilation with an error saying that "candidate template ignored: couldn’t infer… Read More How to infer return type of function returned from a function in c++

Advertisements I was working on this problem on CodeForces. My solution was giving TLE and I could not figure out why. Eventually I narrowed it to the faulty line and it was essentially the following // map<int, set<long long>> res; for(auto z : res) if(res[z.first].count(x)) res[z.first].erase(x); This gives TLE on Test case 6. Now my… Read More C++ STL Map gives TLE when looping with auto?

Advertisements vector<pair<int,char>>alpha; for(int i=0;i<26;i++){ if(letter[i] > 0) { alpha.push_back(pair<int,char>(letter[i],(i+’A’))); } } sort(alpha.begin(),alpha.end()); for(auto& val:alpha){ string str = val.second; } I was trying to convert map value (which was char type) into string type using auto. I need to push those char into string. How could I solve this? >Solution : You could do string str;… Read More How to access and convert pair value?

Advertisements auto data = new char[480][640][3](); char data = new char[480][640][3](); First works. Second doesnt. Why? Isn’t auto supposed to just replace itself with the type of the initializer? >Solution : Because the type isn’t char. The type is char(*)[640][3] and the declaration would be written as char (*data)[640][3] = new char[480][640][3]();