Haskell

Haskell is a functional programming language. It is distinct in a few ways:

• Haskell is pure. A function when invoked using the same arguments will return the same result every time.
• Haskell is lazy. Evaluations are performed only when needed.
• Haskell provides a modern type system with state of the art features like typeclasses and generalized algebraic data types (soon enough, terms like those will roll smoothly off your tongue).

Haskell is enjoyable to use because dealing with pure functions makes code much easier to reason about, and the advanced type system helps catch silly and profound mistakes.

Our aim in this book is to introduce you to the Haskell programming language — from the very basics to advanced features — and to computer programming in general. We urge seasoned programmers to be especially patient with this process. The languages you are familiar with are likely to differ greatly from Haskell, and the habits acquired from those languages might make it difficult to understand how things work — Haskell is simple, but different. Learning to see the world through the warped mindset of a functional programmer is an adventure in a brave new world, which brings knowledge valuable far beyond the boundaries of any language.

The book is divided into three sections: a Beginner’s Track, an Advanced Track, and a section called Haskell in Practice. The last section, which covers practical use cases, depends only on the Beginner’s Track. Seasoned programmers may read the overview to quickly evaluate what makes Haskell unique and different from other languages.