Gain insights into Haskell's functional programming by learning to write pure functions, use pattern matching, recursion, and Lists, define data types, and execute IO operations.

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Functional programming is a problem-solving paradigm that differs drastically from the imperative programming style of languages like C++ or Java. While functional programming principles have invaded most modern programming languages to some degree, there is no language that embraces this paradigm quite as Haskell does. As a result, Haskell code can reach a level of expressiveness, safety, and elegance that is difficult to achieve in other programming languages.

This course will introduce you to the core concepts of functional programming in Haskell. You will learn how to write pure functions using techniques such as pattern matching and recursion, and how to work with Haskell's powerful List data type. You will understand the basics of Haskell's powerful type system and define your own data types. Finally, you’ll learn how to perform IO operations the Haskell way. By the end of this course, you’ll have a new paradigm to add under your belt and you can start using functional programming in your own projects.

Learn Functional Programming in Haskell

In the previous lesson, we started writing simple recursive functions. So far, all the functions that we looked at followed a simple recursive pattern of exactly one recursive call per equation. In this lesson, we will consider functions that require multiple recursive calls.

## Fibonacci numbers

As an example, let's write a function to compute the **Fibonacci** sequence.

The Fibonacci numbers are defined using a recursive equation. The first two Fibonacci numbers are `0` and `1`. The successive numbers are obtained by adding the two previous numbers. This leads to the sequence

$$0, 1, 1, 2, 3, 5, 8, 13, 21, 34...$$

The implementation as a recursive function is straightforward:

In the previous lesson, we started writing simple recursive functions. So far, all the functions that we looked at followed a simple recursive pattern of exactly one recursive call per equation. In this lesson, we will consider functions that require multiple recursive calls.

# Fibonacci numbers

As an example, let's write a function to compute the **Fibonacci** sequence.

The Fibonacci numbers are defined using a recursive equation. The first two Fibonacci numbers are `0` and `1`. The successive numbers are obtained by adding the two previous numbers. This leads to the sequence

$$0, 1, 1, 2, 3, 5, 8, 13, 21, 34...$$

The implementation as a recursive function is straightforward:

In this lesson, we look at recursive functions that do multiple recursive calls.

Introduction

First Steps with Haskell

Techniques for Writing Functions

Working with Lists

Creating Data Types

Input and Output

Conclusion

Appendix

Multiple Recursive Calls

Fibonacci numbers