Basic Functions of String

We already know how functions make our work so simple and organized. Read the 'functions' module if you haven't done so yet. Now we have various functions specific to a string data type that can greatly ease our programming when dealing with strings.

To use these functions we need to import a string header file as the definitions of these functions are provided inside these files.

The functions that we are going to study in this article are:

• length() - finds the length of a string
• insert() - inserts characters into an existing string
• substr() - generates a substring from a string
• swap() - swaps values of two string variables
• String concatenation + - joins two string

Now let's see what these functions are:

'length()' function

As the name suggests, length() function is used to find the length of the given string.

Example

#include <iostream>
#include <string>
using namespace std;
 
int main() {
 
    string text = "String Functions Learnyard";
    cout << "string = " << text << endl;
 
    // text.length() returns the length of string text
    cout << "string length = " << text.length();
    return 0;
}

Try on compiler

Output

string = String Functions Learnyard
string length = 26

Here, #include <string> imports the header file for using string functions and text.length() finds the length of the string named 'text'.

'insert()' function

Suppose there are two strings abcdef and lmnopq. Now I want to insert the second string into the first one after c like: abclmnopqdef . This is what insert() function will help us to achieve.

insert() function of string enables us to insert one string into another string variable. Let's see how.
PS: Don't forget to include the string header file.

Example

#include <iostream>
#include <string>
using namespace std;
 
int main() {
 
    string text1 = "Hello";
    string text2 = "World ";
 
    // insert text2 to index 2 of text1
    text1.insert(2, text2);
 
    cout << text1;
 
    return 0;
}

Try on compiler

Output

HeWorldllo

Quiz

What will be the output of the following code?

#include <iostream>
#include <string>
using namespace std;

int main() {

    string sentence = "The fox";

    sentence.insert(2, "red");

    cout << sentence;

    return 0;
}

'substr()' function

Suppose we have a string as: The painting is beautiful and I want to extract the word painting from this. Might sound a bit complex if done manually but substr() function simplifies this task for us!

Example

#include <iostream>
#include <string>
using namespace std;
 
int main() {
 
    string text = "The painting is beautiful;";
 
    // extract 8 characters from index 4 of text
    string sub_string = text.substr(4, 8);
 
    cout << sub_string;
 
    return 0;
}

Try on compiler

Output

painting

Here,

include <string> imports the header file for string functions

string sub_string = text.substr(4, 8); : This line creates a new string named 'sub_string' that stores the substring of text. To define the range of this substring, we pass the starting index of the substring that we want to create and the length of the substring from the starting index in the substr() function.

In this example, painting starts from 4th index in text and has a length of 8. So we pass these two values in substr() function upon text.

Quiz

What will be the output of the following code?

#include <iostream>
#include <string>
using namespace std;
 
int main() {
 
    string text = "Green Grass";
    string sub_string = text.substr(5, 5);
    cout << sub_string;
 
    return 0;
}

'swap()' function

Very self-explanatory term indeed! We use the swap() function to swap two strings. Let's see an example of the same.

Example

#include <iostream>
using namespace std;
 
int main() {
 
    string text1 = "Happy";
    string text2 = "Sad";
 
    cout << "Before Swapping:" << endl;
    cout << "text1 = " << text1 << endl;
    cout << "text2 = " << text2 << endl;
 
    // swap text1 and text2
    text1.swap(text2);
 
    cout << "\nAfter Swapping:" << endl;
    cout << "text1 = " << text1 << endl;
    cout << "text2 = " << text2;
 
    return 0;
}

Try on compiler

Output

Before Swapping:
text1 = Happy
text2 = Sad

After Swapping:
text1 = Sad
text2 = Happy

Concatenation of strings

Suppose there are 2 strings as aero and plane. We want to join them to achieve a string as aeroplane. To achieve this, we can simply use a + operator.

 + operator is used to concatenate (join) two strings.

Example 

#include <iostream>
using namespace std;
 
int main() {
    
    // create a string
    string text1 = "Aero";
    string text2 = "plane";
  
    // join string
    string joined_string = text1 + text2;
    cout << "Joined string: " << joined_string << endl;
  
    cout << "Individual strings: "<< text1 + " " + text2;
  
    return 0;
}

Try on compiler

Output

Joined string: Aeroplane
Individual strings: Aero plane

Quiz

What will be the output of the following code?

#include <iostream>
using namespace std;

int main() {

    string word1 = "Sun";
    string word2 = "Sets";
    string word3 = "In The";
    string word4 = "West";

    cout << word1 + " " + word2 + word3 + word4;

    return 0;
}

With this, we come to the end of the string module. We have learned a lot of concepts about strings but there's a lot more to learn while practicing these topics. Meet you in the practice section of strings : ) Till then don't feel shy to re-read these articles in case of any confusion or doubts xD