Haskell Quick Syntax Reference

Frontmatter

Chapter 1. Functional Programming

Abstract

Functional programming represents a programming paradigm in which the computations are evaluated by mathematical functions. The paradigm avoids changing states and using mutable data.

Stefania Loredana Nita, Marius Mihailescu

Chapter 2. Static Typing

Abstract

In Haskell, the type system is quite detailed. From a theoretical point of view, it comes from typed Lambda calculus, introduced in 1930 by Alfonso Church,^, where the types are automatically deducted from the way the objects are processed. Such programming languages are statically typed. More precisely, the processing is enforced by and based on the rules of a mathematical type system.

Stefania Loredana Nita, Marius Mihailescu

Chapter 3. GHC

Abstract

GHC stands for Glasgow Haskell Compiler, which is the native code compiler for Haskell. It is open source and can be downloaded from https://www.haskell.org/ghc/ . It is also integrated into the Haskell Platform, available at https://www.haskell.org/downloads#platform . (We recommend you install the Haskell Platform because it contains the compiler, Cabal, and other tools you’ll use in this book.)

Stefania Loredana Nita, Marius Mihailescu

Chapter 4. Types

Abstract

In Chapter 3, you saw that GHC contains predefined functions, and you worked a little with the div function. In that example, we subtly introduced types, without a comprehensive discussion. It is time to discuss them now. So, in this chapter, you’ll learn about the main types in Haskell, how you can define your own types, and how the type system in Haskell works.

Stefania Loredana Nita, Marius Mihailescu

Chapter 5. Tuples

Abstract

Sometimes in your applications you’ll need to group elements. In this chapter, you will learn how to do this using tuples and what the main predefined functions for tuples are.

Stefania Loredana Nita, Marius Mihailescu

Chapter 6. Lists

Abstract

In this chapter, you’ll learn about lists and why are they so useful. You will learn what a list is, which basic functions there are for lists, which operations are faster, and in which context you might use lists.

Stefania Loredana Nita, Marius Mihailescu

Chapter 7. Functions

Abstract

In the previous chapters, you mainly worked with predefined functions from different libraries in Haskell. Now, it’s time to write your own functions. In this chapter, you will learn about pattern matching, guards, clauses, higher-order functions, and lambda expressions used in functions.

Stefania Loredana Nita, Marius Mihailescu

Chapter 8. Recursion

Abstract

In the previous chapter, you learned about functions in Haskell. Many times, in real-world applications you’ll work with functions that recall themselves, which is a process called recursion. In this chapter, you will learn what recursion is, see some concrete examples, and learn how you implement them in Haskell and how to apply recursion on lists.

Stefania Loredana Nita, Marius Mihailescu

Chapter 9. List Comprehension

Abstract

Chapter 6 introduced lists, and now you will learn another way to represent a list. Do you remember how sets are represented using mathematical symbols? Well, you will do that with lists. Further, you will learn more complex functions that you can apply on lists.

Stefania Loredana Nita, Marius Mihailescu

Chapter 10. Classes

Abstract

In the previous chapters, you created your own types. Now, it’s time to learn what classes are in Haskell and how to work with them. In this chapter, you’ll learn about the standard classes and then how to create your own classes.

Stefania Loredana Nita, Marius Mihailescu

Chapter 11. Pattern Matching

Abstract

In Chapter 7, you learned the basics of pattern matching, which is used with functions. In this chapter, you’ll learn more about the details of pattern matching.

Stefania Loredana Nita, Marius Mihailescu

Chapter 12. Monads

Abstract

Monads are important in Haskell, and they are used in many scenarios. The concept of monads can be confusing at first, but in this chapter, you will learn what monads are and how to use them in complex programs.

Stefania Loredana Nita, Marius Mihailescu

Chapter 13. Monad Transformers

Abstract

In the previous chapter, you saw how useful monads are. But what if you need operations from two different monads? In this chapter, you will learn how to proceed in such scenarios.

Stefania Loredana Nita, Marius Mihailescu

Chapter 14. Parsec

Abstract

Now that you know how to work with monads, let’s take a step further. In this chapter, you will learn how to use the Parsec library.

Stefania Loredana Nita, Marius Mihailescu

Chapter 15. Folds

Abstract

An important element in functional programming is the fold (also known as reduce). A fold represents a set of higher-order functions that operate on recursive data structures and take a combining operation as one of the parameters, recombining the results of recursive operations in order to build a return value. In this chapter, you will learn to use fold functions.

Stefania Loredana Nita, Marius Mihailescu

Chapter 16. Algorithms

Abstract

In this chapter, you’ll learn how to implement algorithms such as quicksort, mergesort, and bubblesort.

Stefania Loredana Nita, Marius Mihailescu

Chapter 17. Parsing

Abstract

Wikipedia defines the parsing process as follows:

Stefania Loredana Nita, Marius Mihailescu

Chapter 18. Parallelism and Concurrency

Abstract

Parallelism is a computing strategy that enables many computations (or the execution of processes) to be performed simultaneously. In this chapter, you will learn the basic elements of parallelism and concurrency in Haskell.

Stefania Loredana Nita, Marius Mihailescu

Chapter 19. Haskell Pipes

Abstract

Haskell streaming programs provide great features such as effects, streaming, and composability. In classical programming, you can choose just two of these features. In this chapter, you will learn how to use pipes to achieve all three.

Stefania Loredana Nita, Marius Mihailescu

Chapter 20. Lens

Abstract

In this chapter, you will learn about a particular type of functional reference. First, let’s see define functional reference: reference means you can access and/or modify part of the values, and functional means that the flexibility and composability of functions are assured while accessing these parts.

Stefania Loredana Nita, Marius Mihailescu

Chapter 21. Lazy Evaluation

Abstract

You already know that Haskell is based on lazy evaluation. This means that the expressions are evaluated only when it is necessary. But what is “necessary”? In this chapter, you will get an answer to that question, and you will take a deeper look at lazy evaluation in Haskell.

Stefania Loredana Nita, Marius Mihailescu

Chapter 22. Performance

Abstract

Sometimes your program will need to meet some requirements for space and time execution. It is really important to know how the data is represented, what lazy evaluation or strict evaluation involves, and how to control the space and time behavior. In this chapter, you will learn basic techniques to improve the performance of your programs.

Stefania Loredana Nita, Marius Mihailescu

Chapter 23. Haskell Stack

Abstract

Haskell Stack is a tool used to build Haskell projects and to handle its dependencies, including GHC, Cabal, a version of the Hackage repository, and a version of the Stackage package collection tool. In this chapter, you will learn the main uses of Haskell Stack.

Stefania Loredana Nita, Marius Mihailescu

Chapter 24. Yesod

Abstract

Yesod is a web framework based on Haskell for the professional development of type-safe, REST model–based, high-performance web applications.

Stefania Loredana Nita, Marius Mihailescu

Chapter 25. Haskell Libraries

Abstract

In programming, libraries are collections of precompiled routines that can be used in other programs. Usually, a library stores frequently used routines (for example, reading or printing an input), or it is specialized for a particular subject (for example, the libraries used in the statistics field). In this chapter, you will learn about the main libraries in Haskell and when you can use them to create powerful programs.

Stefania Loredana Nita, Marius Mihailescu

Chapter 26. Cabal

Abstract

Haskell includes a standard package system called Cabal, which is used to configure, build, install, and (re)distribute Haskell software. In this chapter, you will learn how to use Cabal to increase your productivity.

Stefania Loredana Nita, Marius Mihailescu

Backmatter