3.2Library string Type

• string s7 = "hello" + ", " + s2; // error: can't add string literals

• string s("Hello World!!!");// punct_cnt has the same type that s.size decltype(s.size()) punct_cnt = 0; // count the number of punctuation characters in sfor(autoc:s) if (ispunct(c))++punct_cnt; cout << punct_cnt// forevery char in s// if the character is punctuation// increment the punctuation counter<< " punctuation characters in " << s << endl;

  
  

• string s("Hello World!!!");// convert s to uppercasefor (auto &c : s) // for every char in s (note: c is a reference)c = toupper(c); // c is a reference, so the assignment changes the char in scout << s << endl;

  
  

  
  
• cctype header includes some operations like ispunct(), toupper().  

• for (decltype(s.size()) index = 0;index != s.size() && !isspace(s[index]); ++index) s[index] = toupper(s[index]); // capitalize the currentcharacter

  
  

  
  

• The subscript operator onvector(andstring) fetches an existingelement; it does not add an element. 

  vector<int> ivec; // empty vectorfor (decltype(ivec.size()) ix = 0; ix != 10; ++ix)ivec[ix] = ix; // disaster: ivec has no elements

  However, it is in error:ivecis an emptyvector; there are no elements to subscript!

  As we’ve seen, the right way to write this loop is to usepush_back: 

  for (decltype(ivec.size()) ix = 0; ix != 10; ++ix) ivec.push_back(ix); // ok: adds a new element with value ix