C++ Manipulating Strings

A string is a sequence of character. As you know that C++ do not support built in string type, you have use earlier those null character based terminated array of characters to store and manipulate strings. These strings are termed as C Strings. It often become inefficient performing operations on C strings. Programmers can also define their own string classes with appropriate member functions to manipulate strings. ANSI standard C++ introduces a new class called string which is an improvised version of C strings in several ways. In many cases, the strings object may be treated like any other built in data type. String is treated as another container class for C++.

The C Style String

The C style string belongs to C language and continues to support in C++ also strings in C are one dimensional array of characters which gets terminated by \0 (null character).

This is how the strings in C are declared:

char ch[6] = {'H', 'e', 'l', 'l', 'o', '\0'};

Actually, you do not place the null character at the end of a string constant. The C++ compiler automatically places the \0 at the end of the string when it initializes the array.

String Class in C++

The string class is very huge and includes many constructors, member functions and operators.

Programmers may use the constructors, operators and member functions to achieve the following:

• Creating string objects
• Reading string objects from keyboard
• Displaying string objects to the screen
• Finding a substring from a string
• Modifying string
• Adding objects of string
• Comparing strings
• Accessing characters of an string
• Obtaining the size or length of string, etc…

Manipulate Null-terminated strings

C++ supports a wide range of functions that manipulate null-terminated strings. These are:

• strcpy(str1, str2): Copies string str2 into string str1.
• strcat(str1, str2): Concatenates string str2 onto the end of string str1.
• strlen(str1): Returns the length of string str1.
• strcmp(str1, str2): Returns 0 if str1 and str2 are the same; less than 0 if str1<str2; greater than 0 if str1>str2.
• strchr(str1, ch): Returns a pointer to the first occurrence of character ch in string str1.
• strstr(str1, str2): Returns a pointer to the first occurrence of string str2 in string str1.

Important functions supported by String Class

• append(): This function append a part of string to another string
• assign():This function assigns a partial string
• at():This function obtains the character stored at a specified location
• begin():This function returns a reference to the start of the string
• capacity():This function gives the total element that can be stored
• compare():This function compares string against the invoking string
• empty(): This function returns true if the string is empty
• end():This function return a reference to the end of the string
• erase():This function remove character as specified
• find():This function searches for the occurrence of a specified sub string
• length(): It gives the size of string or the number of elements of a string
• swap():This function swaps the given string with the invoking one

Important Constructors obtained by String Class

• String(): This constructor is used for creating an empty string
• String(const char *str): This constructor is used for creating string objects from a null terminated string
• String(const string *str): This constructor is used for creating a string object from another string object

Operators used for String Objects

1. =: assignment
2. +: concatenation
3. ==: Equality
4. !=: Inequality
5. <: Less than
6. <=: Less than or equal
7. >: Greater than
8. >=: Greater than or equal
9. []: Subscription
10. <<: Output
11. >>: Input