~cpp #include <iostream> #include <string> // say what standard-library names we use using std::cin; using std::cout; using std::string; using std::endl; int main() { // ask for person's name cout << "Please enter your first name: "; // read the name string name; cin >> name; // build the message that we intend to write const string greeting = "Hello, " + name + "!"; // the number of blacks surrounding the greeting const int pad = 1; // the number of rows and columns to write const int rows = pad * 2 + 3; const string::size_type cols = greeting.size() + pad * 2 + 2; // write blank line to separate the output from the input cout << endl; // write rows // invariant: we have written r rows so far for (int r = 0; r != rows ; ++r) { string::size_type c = 0; // invariant: we have written c while (c != cols) { // is it time to write the greeting? if (r == pad + 1 && c == pad + 1) { cout << greeting; c += greeting.size(); } else { // are we on the border? if (r == 0 || r == rows - 1 || c == 0 || c == cols - 1) cout << "*"; else cout << " "; ++c; } } cout << endl; } return 0; }
~cpp // invariant : we have written r rows so far int r = 0; // setting r to 0 makes the invariant true while( r != rows ) { // we can assume that the invariant is true here // writing a row of output makes the invariant false std::cout << std::endl; // incrementing r makes the invariant true again ++r; } // we can conclude that the invariant is true here코드의 마지막 부분에서 invariant 가 다시 true 로 되는것일까요.? invariant 가 무엇인지 아직 개념이 잡히지 안아서. -_-a - 임인택