Advertisements I have uint16_t integers in the range [ 0 .. 4092 ] and I need to scale them into [ 0 .. 255 ] interval. What’s the correct formula for that? The obvious one y = x * 255 / 4092 doesn’t work because the scaling factor is 15.988 so I need 15-16 (usually… Read More How to correctly scale integers between intervals?

Advertisements Here is a minimal working example: #include <iostream> #include <sstream> int main() { std::stringstream ss; unsigned int output; ss << "0xBB"; ss >> std::hex >> output; std::cout << output << std::endl; ss << "0xAA"; ss >> std::hex >> output; std::cout << output; } I would expect final output to have decimal value of 0xAA,… Read More Why doesn't stringstream consume output during hex formatting?

Advertisements The fifth edition of c++ primer describes weak_ptr like this： A weak_ptr is a smart pointer that does not control the lifetime of the object to which it points.Instead,a weak_ptr points to an object that is managed by a shared_ptr. But why dot operators are used instead of -> when operations such as reset,… Read More Obviously it is a pointer, why use the dot operator

Advertisements A big array on the heap, initialized like this: double* vx = new double[1024/8 * 1024 * 1024]; wants to be directly saved to a file like this: file.write((char*)&vx, sizeof(1024 / 8 * 1024 * 1024)); This only writes the first value but the idea should be clear. >Solution : vx is already a… Read More whole big array from heap to file without for loop in C++

Advertisements I’m enjoying learning about metaprogramming, and started find out about some features, I can’t make the call to at works which takes an index to return a type that mapped to varidiac positoin. #include <iostream> #include <type_traits> #include <utility> template <typename…> struct type_list {}; template<typename T ,typename… Ns> auto pop_front(type_list<T, Ns…>t) { return type_list<Ns…>{};… Read More How to return a type that mapped to varidiac positoin

Advertisements I have this sequence of numbers stored in a vector: 4 7 2 6 5 1 3. In this case, the longest sequence will be: 1,3,4,7. That’s 4 numbers. I only need to get the value of the longest increasing sequence(in this case 4). I have this code: using namespace std; ifstream f("roboti2.in"); ofstream… Read More how can i get the longest sequence of increasing numbers from a vector in c++?

Advertisements Say I have the following code class C { static const int dim = 3; static const int matrix[dim][dim]; }; int dim = -2; const int C::matrix[dim][C::dim] = {{1,2,3}, {1,2,3}, {1,2,3}}; Why am I obliged to state the dimensions of the matrix again? Why does the first dim = 3 and not -2? My… Read More Scope of dimension parameters of outside-of-class defined matrix

Advertisements #include <iostream> #include <vector> using namespace std; int main() { vector<string> v = {"a", "a", "a"}; for(int i = 0; i < 3; i++) { switch(v[i][0]) { case ‘a’: cout<<"case a"<<"\n"; case ‘b’: cout<<"case b"<<"\n"; case ‘c’: cout<<"case c"<<"\n"; } } } Output: C:\Users\Administrator\calc>g++ test.cpp && a.exe case a case b case c case… Read More erroneous output while using switch() with a char from vector string

Advertisements So i am using find in the algorithm library of C++ to check if each character in a string is present in a string vector, but the problem i am facing with the find function is that this does not work: #include <iostream> #include <algorithm> #include <vector> using namespace std; int main() { string… Read More find() not working for a character in a string (C++)

Advertisements I have a text file with a single line that stores the memory address to a variable (of type double) being used in the code. Content of temp.txt: 0x7f3c00844c00 I would like to read this line and dereference it to get the double value stored at the address (i.e. 0x7f3c00844c00) This is what I… Read More C++: get value of memory address from a text file