Book Image

Learning Functional Data Structures and Algorithms

By : Raju Kumar Mishra
Book Image

Learning Functional Data Structures and Algorithms

By: Raju Kumar Mishra

Overview of this book

Functional data structures have the power to improve the codebase of an application and improve efficiency. With the advent of functional programming and with powerful functional languages such as Scala, Clojure and Elixir becoming part of important enterprise applications, functional data structures have gained an important place in the developer toolkit. Immutability is a cornerstone of functional programming. Immutable and persistent data structures are thread safe by definition and hence very appealing for writing robust concurrent programs. How do we express traditional algorithms in functional setting? Won’t we end up copying too much? Do we trade performance for versioned data structures? This book attempts to answer these questions by looking at functional implementations of traditional algorithms. It begins with a refresher and consolidation of what functional programming is all about. Next, you’ll get to know about Lists, the work horse data type for most functional languages. We show what structural sharing means and how it helps to make immutable data structures efficient and practical. Scala is the primary implementation languages for most of the examples. At times, we also present Clojure snippets to illustrate the underlying fundamental theme. While writing code, we use ADTs (abstract data types). Stacks, Queues, Trees and Graphs are all familiar ADTs. You will see how these ADTs are implemented in a functional setting. We look at implementation techniques like amortization and lazy evaluation to ensure efficiency. By the end of the book, you will be able to write efficient functional data structures and algorithms for your applications.
Table of Contents (20 chapters)
Learning Functional Data Structures and Algorithms
Credits
About the Authors
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface

Complexities and collections


Let's look at collections and see how complexity helps us to see how they will perform in different situations. We will look at commonly used collections and idioms.

The sliding window

The sliding method allows us to create a sliding window. Here's an example:

scala> val list = List(1,2,3,4,5,6) 
list: List[Int] = List(1, 2, 3, 4, 5, 6) 
 
scala> val list1 = list.sliding(2,1).toList 
list1: List[List[Int]] = List(List(1, 2), List(2, 3), List(3, 4), List(4, 5), List(5, 6)) 

This creates List[Int]. Each element of List contains the current element and its successor in the original list.

Here is the equivalent code in Clojure:

user=> (partition 2 1 '(1 2 3 4 5 6)) 
((1 2) (2 3) (3 4) (4 5) (5 6)) 

It gives us similar results:

Let's see the complexity of this sliding window code. The time complexity is O(n). We need to visit each element of the original list twice: once when it is the first element, and second, when it is the second element. This is clearly...