<string>  -  a reference

<string> class

 
- Required header file:
 

#include <string>

using namespace std;

 

- The operators, =, ==, >, >=, <, <=, != +, +=, [i] work with strings.
    =    copies one string into another (similar to strcpy in C)
    ==  tests if two strings have the same characters (case sensitive)
    +    concatenates two strings together, creating a new string
    +=  appends the right string onto the end of the left string
    string[i]  gets the character at index number i in the string

  stringA = "any string literal";
  stringA = stringB;
  // also you can write:
  stringA.assign(stringB);
 
  stringC[2] = 'r';

  if(stringD == stringE)
    cout << "strings match!" << endl;

  if(stringD > stringE)
    cout << "stringD lexigraphically greater than stringE"
         << endl;

  stringF = stringG + stringH;

  stringI += "any string literal";
  stringI += stringK;
  // also you can write:
  stringI.append("stringK");

 

- Constructors:

  string stringA;  // creates an empty string
  string stringB("initial string");
  string stringC(stringB);  // copy constructor
  string stringD = "initial string";
  string stringE(a_c_string);
  string stringF(n, c); // where c is a character and
                        //    n is the number of times
                        //    c is repeated.
 

- Size and length:

  stringA.size() // returns the number of characters (int)
  stringA.length() // exactly the same as stringA.size()
  stringB.empty()  // returns if string is 0 length (bool)
 

- C_strings from C++ strings:

  char* a_c_string_pointer;
  a_c_string_pointer = stringA.c_str();

  char  a_c_string[256];
  stringA.copy(a_c_string, n);     // copy into a_c_string
  stringA.copy(a_c_string, n, i); // n -- number of chars
                                  // i -- starting index
                                  
 

- Inserting another string at a specific index (size of stringA grows):

  stringA.insert(i, a_cpp_string);  // i -- starting index
  stringA.insert(i, a_c_string);
 
 

- Replacing with another string at a specific index (size of stringA remains the same):

  stringA.replace(i, m, a_cpp_string); // i -- start index
  stringA.replace(i, m, a_c_string); // m -- max number
                                     //  of chars replaced
 

- Erasing characters:

  stringA.clear(); // erase all characters. stringA is empty.
  stringA.erase(); // same as stringA.clear()
  stringA.erase(i); // erase all characters starting at index i
  stringA.erase(i, n); // erase n characters starting at i
 

- Extracting a substring (all functions return a string):

  substringA = stringA.substr(i); // starting at index i
  substringA = stringA.substr(i, n);// n characters long,
                                    // starting at index i
 

- Finding a whole substring (all functions return the integer index of substring found --
                                             They return  string::npos  if the substring is not found)

  if ( (index = stringA.find(substring)) == string::npos)
     cout << "substring not found" << endl;
  else
     cout << "substring found at index " << index << endl;
 

  index = stringA.find(c);    // c is a character
  index = stringA.rfind(c);   // search backwards
  index = stringA.find(substring); // substring is a string
  index = stringA.rfind(substring); // search backwards
  index = stringA.find(c_string);   // c_string is char*
  index = stringA.rfind(c_string);  // search backwards

  index = stringA.find(c, i);  // start at index i
  index = stringA.rfind(c, i); // start at i, search
                               //   forwards 
  index = stringA.find(substring, i); 
  index = stringA.rfind(substring, i);
  index = stringA.find(c_string, i); 
  index = stringA.rfind(c_string, i);

  index = stringA.find(c, i, n); // search at most n chars
  index = stringA.rfind(c, i, n);  
  index = stringA.find(substring, i, n); 
  index = stringA.rfind(substring, i, n);
  index = stringA.find(c_string, i, n); 
  index = stringA.rfind(c_string, i, n);

 

- Find the first or last character that is contained in another string (returns the index --
                                                      or  string::npos  if none of the characters is found)  

  if ( (index = stringA.find_first_of(other)) == string::npos)
     cout << "no characters from other string found" << endl;
  else
     cout << "first character found at index " << index << endl;
 

  index = stringA.find_first_of(c);  // c is a character
  index = stringA.find_last_of(c);  
  index = stringA.find_first_of(other); // other is a string
  index = stringA.find_last_of(other);
  index = stringA.find_first_of(c_string); // c_string is char*
  index = stringA.find_last_of(c_string);

  index = stringA.find_first_of(c, i);  // start at index i
  index = stringA.find_last_of(c, i);  
  index = stringA.find_first_of(other, i); 
  index = stringA.find_last_of(other, i);
  index = stringA.find_first_of(c_string, i); 
  index = stringA.find_last_of(c_string, i);


 

- Find the first or last character that is absent from another string (returns the index --
                                                      or  string::npos  if one of the characters is found)  

  if ((index=stringA.find_first_not_of(other)) == string::npos)
     cout << "all characters in stringA are in other string";
  else
     cout << "first character not found";
 

  index = stringA.find_first_not_of(c); // c is a character
  index = stringA.find_last_not_of(c);  
  index = stringA.find_first_not_of(other);// other is a string
  index = stringA.find_last_not_of(other);
  index = stringA.find_first_not_of(c_string);// char* c_string
  index = stringA.find_last_not_of(c_string);

  index = stringA.find_first_not_of(c, i);  // start at index i
  index = stringA.find_last_not_of(c, i);  
  index = stringA.find_first_not_of(other, i); 
  index = stringA.find_last_not_of(other, i);
  index = stringA.find_first_not_of(c_string, i); 
  index = stringA.find_last_not_of(c_string, i);

 

More Information:

Deitel and Deitel, Chapter 16.