Kotlin Sequence distinct Function

The distinct function in Kotlin is used to return a sequence containing only distinct elements from the original sequence. It is part of the Kotlin standard library and allows you to filter out duplicate elements, ensuring that each element in the sequence is unique.

Table of Contents

1. Introduction
2. distinct Function Syntax
3. Understanding distinct
4. Examples
   • Basic Usage
   • Distinct Strings
   • Using distinct with Custom Objects
   • Chaining distinct with Other Functions
5. Real-World Use Case
6. Conclusion

Introduction

The distinct function allows you to filter out duplicate elements from a sequence, leaving only unique elements. This is useful for scenarios where you need to ensure that a sequence contains no duplicate elements, enabling cleaner and more accurate data processing.

distinct Function Syntax

The syntax for the distinct function is as follows:

fun <T> Sequence<T>.distinct(): Sequence<T>

Returns:

• A sequence containing only distinct elements from the original sequence.

Understanding distinct

The distinct function works by comparing the elements of a sequence and filtering out duplicates. The resulting sequence contains only unique elements, preserving their original order.

Examples

Basic Usage

To demonstrate the basic usage of distinct, we will create a sequence of integers with duplicate values and filter out the duplicates.

Example

fun main() {
    val numbers = sequenceOf(1, 2, 2, 3, 4, 4, 5)
    val distinctNumbers = numbers.distinct()
    println(distinctNumbers.toList()) // Output: [1, 2, 3, 4, 5]
}

Output:

[1, 2, 3, 4, 5]

Distinct Strings

This example shows how to filter out duplicate strings from a sequence.

Example

fun main() {
    val names = sequenceOf("Arjun", "Bhaskar", "Arjun", "Chitra", "Deepak", "Chitra", "Esha")
    val distinctNames = names.distinct()
    println(distinctNames.toList()) // Output: [Arjun, Bhaskar, Chitra, Deepak, Esha]
}

Output:

[Arjun, Bhaskar, Chitra, Deepak, Esha]

Using distinct with Custom Objects

You can use the distinct function to filter out duplicate custom objects based on their properties.

Example

data class Person(val name: String, val age: Int)

fun main() {
    val people = sequenceOf(
        Person("Arjun", 25),
        Person("Bhaskar", 30),
        Person("Arjun", 25),
        Person("Chitra", 22),
        Person("Deepak", 28),
        Person("Chitra", 22),
        Person("Esha", 26)
    )
    val distinctPeople = people.distinct()
    println(distinctPeople.toList()) // Output: [Person(name=Arjun, age=25), Person(name=Bhaskar, age=30), Person(name=Chitra, age=22), Person(name=Deepak, age=28), Person(name=Esha, age=26)]
}

Output:

[Person(name=Arjun, age=25), Person(name=Bhaskar, age=30), Person(name=Chitra, age=22), Person(name=Deepak, age=28), Person(name=Esha, age=26)]

Chaining distinct with Other Functions

The distinct function can be chained with other sequence functions to perform more complex operations.

Example

fun main() {
    val numbers = sequenceOf(1, 2, 2, 3, 4, 4, 5)
    val result = numbers.map { it * 2 }
                        .distinct()
                        .filter { it > 5 }
    println(result.toList()) // Output: [6, 8, 10]
}

Output:

[6, 8, 10]

Real-World Use Case

Filtering Unique Products

In real-world applications, the distinct function can be used to filter out duplicate products based on their properties, such as name and price.

Example

data class Product(val name: String, val price: Double)

fun main() {
    val products = sequenceOf(
        Product("Laptop", 999.99),
        Product("Smartphone", 499.99),
        Product("Laptop", 999.99),
        Product("Tablet", 299.99),
        Product("Smartwatch", 199.99),
        Product("Tablet", 299.99)
    )

    val distinctProducts = products.distinct()
    println(distinctProducts.toList()) // Output: [Product(name=Laptop, price=999.99), Product(name=Smartphone, price=499.99), Product(name=Tablet, price=299.99), Product(name=Smartwatch, price=199.99)]
}

Output:

[Product(name=Laptop, price=999.99), Product(name=Smartphone, price=499.99), Product(name=Tablet, price=299.99), Product(name=Smartwatch, price=199.99)]

Conclusion

The distinct function in Kotlin provides used for filtering out duplicate elements in a sequence. By understanding and using the distinct function, you can efficiently manage and process data in your Kotlin applications, ensuring that sequences contain only unique elements.