/* * Author - ~swim~ * Created - 20-Apr-2018 Description : Create a program that takes 3 inputs, a lower bound, an upper bound and the expression. Calculate the sum of that range based on the given expression and output the result. For Example: Input: 2 4 *2 Output: 18 (2*2 + 3*2 + 4*2) Input: 1 5 %2 Output: 3 (1%2 + 2%2 + 3%2 + 4%2 + 5%2) Note - Input validation not done Input - Enter space separated/on new line, start range, stop range, operator to apply and the value to apply e.g 2 6 *3 */ #include #include #include #include #include #include #include using namespace std; using VA = valarray; // map of operator to function // function<> acts a wrapper // for pointer to function. // One can use pointer to function // directly as // double(*)(double, double) map> Opmap { // Add {"+",[](VA va, double sc){ return (va += sc).sum();}}, // Subtract {"-",[](VA va, double sc){ return (va -= sc).sum();}}, // Multiply {"*",[](VA va, double sc){ return (va *= sc).sum();}}, // Divide {"/",[](VA va, double sc){ return (va /= sc).sum();}} }; auto Print=[](auto start, auto stop, auto oper, auto Result) { cout << "Result of operator \"" << oper.substr(0,1) << "\"" << " with scalar " << oper.substr(1) << " on Range(" << start << ", " << stop << ") = " << Result << "\n\n"; }; int main() { double start; // start range double stop; // stop range string oper; // operation to // apply // with scalar // read the input cin >> start >> stop >> oper; // extract the scaler and convert // to double double sc{}; stringstream ss(oper.substr(1)); ss >> sc; // generate the range VA seq(stop-start +1); iota(begin(seq),end(seq), start); // call the function try { auto res= Opmap[oper.substr(0,1)] (seq,sc); Print(start,stop, oper, res); } catch(std::bad_function_call) { cout << "invalid/unkown" " operator specified!" << "\n\n"; } // end catch // add new operator "%" cout << ("adding operator \"%\"" " to operator map and " "applying it to input " "\n\n"); // Modulus // fmod is used because arguments // are valarray of double and // double and for double/float // "%" (modulus) is not defined in // C/C++ Opmap["%"]=[=](VA seq, double sc) { for(int i=1;i<=seq.size(); ++i) //for(auto& e: seq) seq[i-1] = fmod(seq[i-1],sc); return seq.sum(); }; oper = "%3"; double res = Opmap[oper.substr(0,1)] (seq,sc); Print(start,stop, oper, res); return 0; } // end main

Summation Calculator.cpp