#include #include #include #include using namespace std; class Calculator { public: Calculator(); bool input(); double calc(); private: string m_uInput; regex m_opAv; // available operations }; Calculator::Calculator(): m_opAv("[(-|\\+)?\\d+.\\d+(\\+|-)]+") { } bool Calculator::input() { getline(cin, m_uInput); return regex_match(m_uInput, m_opAv); } double Calculator::calc() { // check multiplication and division priotery double result(0); for (int i (0); i < m_uInput.size(); i++) { if (m_uInput[i] == '*') { m_uInput[i] = ' '; string s = m_uInput.substr(i - 1, 3); istringstream in; in.str(s); double tab[2], a; in >> a; tab[0] = a; in >> a; tab[1] = a; a = tab[0] * tab[1]; s = m_uInput.substr(0, i - 1); ostringstream out; out << a; s += out.str(); m_uInput.erase(0, i + 2); s += m_uInput; m_uInput = s; s.erase(); } if (m_uInput[i] == '/') { m_uInput[i] = ' '; string s = m_uInput.substr(i - 1, 3); istringstream *in = new istringstream; in->str(s); double tab[2], a; *in >> a; tab[0] = a; delete in; in = new istringstream; for (int j (0); j < s.size(); j++) { if (s[j] == '/') { s.erase(0, j); } } in->str(s); *in >> a; tab[1] = a; a = tab[0] / tab[1]; s = m_uInput.substr(0, i - 1); ostringstream out; out << a; s += out.str(); m_uInput.erase(0, i + 2); s += m_uInput; m_uInput = s; s.erase(); } } istringstream in; in.str(m_uInput); double a(0); while (in >> a) { result += a; } return result; } int main() { Calculator c; if (c.input()) { cout << "The result is: "; cout << c.calc() << endl; } else { cout << "Bad input please try again" << endl; } return 0; }