Strings in C++

Youkoso!

Here's Traditional Way (C Language)

• We use null-terminated (\0) character array, although it is not technically a data type.
• So, Operators cannot be applied to them, like assignment and comparison operators =, <, >, <=, >=.

// Declaration of character array
char s1[10], s2[10];
s1[10] = "Doge";

// Error Full Code (Don't use at home/work)
s2 = s1;
s2 > s1;
s3 = s1 + s2;

This code results in invalid array operations.

Strings in C++

• The string class is a expertise class of a more general template called basic_string.
• Since defining a class in C++ is creating a new data type, string is derived data type.
• This means operators can be overloaded for this class.

syntax

class string{
   // Variables
   // functions
   // operators
}

string s1;
s1.function();
s1.operator(arguments);

string operations are safe but time consuming. So, 'char array' (speedy, less operations) concept is not deprecated.

if (speed matters) {

Use character array

}else if (safety and easy manipulation matters) {

Use string class }

Here's why string is safer than character array

• Careless programmers, can overrun to the end of an array that holds a null terminated (null character \0) string.
• for example - see below
• string class handles such issues.

char s3[10];
strcpy(s3,"Hello careful programmers.");

String is also in STL (but concept of string is thought apart from STL concepts)

• string is an another container class.

• To use string class, we have to include string header class. (not string.h)

  • #include<string> (for string header class)
  • #include<string.h> (in C, for string functions applied on character array)

String class supports many constructors as follows.

• string()
• string(const char *str)
• string(const string &str)

Operators

• = (assignment)
• + (concatenation)
• += (concatenation assignment)
• == (equality)
• != (inequality)
• < (less than)
• <= (less than equal to)
• > (greater than)
• >= (greater than equal to)
• [] (subscripting)
• << (insertion)
• >> (extraction)

Mixed Operations

• We can mix string objects with another string object or C style string.
• C++ string can also be concatenated with character const.

Useful methods

• assign()
• append()
• insert()
• replace()
• erase()
• find()
• rfind()
• compare()
• c_str()
• size()

Visit :

• strings.cpp
• Templates in C++

ittekimasu! :)