1 Principles of Computer Science I Honors Section Note Set 10 CSE 1341

2 Today String Streams

3 What’s the difference between: 255 and “255” ??????????

4 Background VAB Web Cam pictures Rover Communcations Mission Control (YOU)

5 Background Communication in character strings –s –Sent to the robot as a string of characters Problem: –You have to build the string of characters before you can send it to the robot –You have to interpret the string of characters from the VAB worksheet before you can use them in calculations

6 Numbers to Strings Difficult/annoying with c-strings (null terminated char arrays) Difficult to append a number to a c-string or stl-string //Can’t Do this string s; s = 32; cout << s; //WILL NOT display 32a //Can’t Do this either char str[25]; strcpy(str, 32); //WILL NOT COMPILE cout << s;

7 c-way or old way atoi(const char*), atof(const char*) –will convert an ascii string of digits to an integer –have to worry about c-string being properly formatted –What if result is too big to fit in an integer??

8 Remember cout??? You can send any fundamental data type to cout //This is OK! cout << 32; cout << “32”; cout << “go forward”; cout << 3.456; Can we do something similar, but store the data in a string instead of sending it to the screen?

9 String Stream string stream objects handle (behind the scenes) conversion of data types Can insert or extract information from a string stream using >> and << Stored in a String behind the scenes stringstream ss; istringstream iss; ostringstream oss;

10 Example #include int main() { stringstream s; int x = 25; double y = 2.34; s << x; s << “ “; s << y; string str; s >> str; //like cin, but source is s cout << str; //What will this print??? return 0; }

11 Example stringstream ss; ss << “ ”; int temp; for (int i = 0; i < 6; i++) { ss >> temp; cout << temp * 2; }

Example stringstream ss; char str[] = “ ”; ss << str; int temp; for (int i = 0; i < 6; i++) { ss >> temp; cout << temp * 2; }

13 Functions str() –return a stl-string copy of what’s in the stringstream getline(…) –used as if you were getting a line from cin

14 Example stringstream ss; string temp; ss << "C++ is the best ever!"; ss >> temp; cout << temp; cout << endl; getline(ss, temp); cout << temp; C++ is the best ever!

15 Questions??? ?