Append and Insert Functions of String Class in C++

Append and Insert Functions of String Class in C++

In this article, I am going to discuss Append and Insert Functions of String Class in C++ Language with examples. Please read our previous article, where we discussed the Basic Functions of the String Class in C++ with examples.

Append and Insert Functions of String Class in C++

In this article, we will understand various member functions of the C++ String class. Already we have seen some basic functions in our previous article. We will explain the following functions one by one.

Append and Insert Functions of String Class in C++

append() Function of String Class in C++:

The first function is append. This function will add new content to a string. Suppose we have a string,

append() Function of String Class in C++

In this string, we want to add some new words or characters. Then we will use the append function as “str1.append(“Roy”)”.

Append and Insert Functions of String Class in C++ Language with examples

Then “Roy” will be appended to this string and the string will become “HelloRoy”. Already we have seen that we have a string then the capacity is more than the size. In this string, we have more spaces also, so now the word “Roy” will be stored in that vacant spaces that are three spaces after this ‘Hello’ and if it requires it may increase the size. Actually, it will not increase the same array size, it will create a bigger size array and it will store it there.

So can’t say how this function works. This append function will handle. How it is defined inside the compiler we can’t see that. Let us see this function in the program.

Program for append function in C++:
#include <iostream>
#include <string>
using namespace std;
int main()
{
    string str = "Hello";
    cout << "Before appending: " << str.capacity () << endl;
    str.append ("Roy");
    cout << "After appending: " << str.capacity () << endl;
    cout << str << endl;
}
Output:

Program for append function in C++

You can see that capacity before append and after append is the same as we have not appended a large string. Now let’s see what happens if we append a large word or string.

Program for appending a large string using append function in C++:
#include <iostream>
#include <string>
using namespace std;
int main()
{
    string str = "Hello";
    cout << "Before appending: " << str.capacity () << endl;
    str.append (" Roy! How are you?");
    cout << "After appending: " << str.capacity () << endl;
    cout << "Length: " << str.length () << endl;
    cout << str << endl;
}
Output:

Program for appending a large string using append function in C++

As we have given a larger string so the capacity of the string is increased. Now let us continue with the next function i.e. Insert.

insert() Function of String Class in C++:

This function will insert a given string at a given index. Suppose we have a string,

insert() Function of String Class in C++

In this string, we want to insert “Roy” at index ‘0’ onwards. So, we will write, insert(0, “Roy”).

Append and Insert Functions of String Class in C++ Language with examples

Here “Roy” is inserted at the ‘0’ index. We can insert it at any location. Insert function takes 2 parameters, first is the index at where we want to insert in a string and second is the word or string which we want to insert.

There is another version of the insert function that is “insert(0, “Apple”, 2)”. This is taking 3 parameters. The first 2 parameters are the same but the last one is the total character we want to insert from the given word or string like “Apple”, so it will insert starting 2 characters from the word “Apple”. Now let us see this in the program.

Program for insert function in C++:
#include <iostream>
#include <string>
using namespace std;
int main()
{
    string str = "Hello";
    cout << "Before Insert: " << str.capacity () << endl;
    str.insert (0, "Roy ");
    str.insert (9, ", How are you?");
    cout << "After Insert: " << str.capacity () << endl;
    cout << "Length: " << str.length () << endl;
    cout << str << endl;
}
Output:

Program for insert function in C++

Now let us see another version of the insert.

Program:
#include <iostream>
#include <string>
using namespace std;
int main()
{
    string str = "How you?";
    cout << "Before Insert: " << str.capacity () << endl;
    str.insert (3, " area", 4);
    cout << "After Insert: " << str.capacity () << endl;
    cout << "Length: " << str.length () << endl;
    cout << str << endl;
}
Output:

Append and Insert Functions of String Class in C++ Language with examples

In the next article, I am going to discuss Replace and Swap Functions of String Class in C++ with examples. Here, in this article, I try to explain Append and Insert Functions of String Class in C++ Language with examples. I hope you enjoy this Append and Insert Functions of String Class in C++ with examples article. I would like to have your feedback. Please post your feedback, question, or comments about this article.

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