Haskell in Depth

Haskell in Depth
brief contents
contents
foreword
preface
	Functional programming
	Type system
	Lazy evaluation
	Tooling around Haskell
	What can be done using Haskell: Libraries
acknowledgments
about this book
	Who should read this book
	How this book is organized: A roadmap
	About the code
	Getting the sources
	Using cabal
	Using stack
	liveBook discussion forum
about the author
about the cover illustration
Part 1: Core Haskell
	Chapter 1: Functions and types
		1.1 Solving problems in the GHCi REPL with functions
		1.2 From GHCi and String to GHC and Text
		1.3 Functional programs as sets of IO actions
		1.4 Embracing pure functions
			1.4.1 Separating I/O from pure functions
			1.4.2 Computing the most frequent words by sorting them
			1.4.3 Formatting reports
			1.4.4 Rule them all with IO actions
	Chapter 2: Type classes
		2.1 Manipulating a radar antenna with type classes
			2.1.1 The problem at hand
			2.1.2 Rotating a radar antenna with Eq, Enum, and Bounded
			2.1.3 Combining turns with Semigroup and Monoid
			2.1.4 Printing and reading data with Show and Read
			2.1.5 Testing functions with Ord and Random
		2.2 Issues with numbers and text
			2.2.1 Numeric types and type classes
			2.2.2 Numeric conversions
			2.2.3 Computing with fixed precision
			2.2.4 More about Show and Read
			2.2.5 Converting recursive types to strings
		2.3 Abstracting computations with type classes
			2.3.1 An idea of a computational context and a common behavior
			2.3.2 Exploring different contexts in parallel
			2.3.3 The do notation
			2.3.4 Folding and traversing
	Chapter 3: Developing an application: Stock quotes
		3.1 Setting the scene
			3.1.1 Inputs
			3.1.2 Outputs
			3.1.3 Project structure
		3.2 Exploring design space
			3.2.1 Designing the user interface
			3.2.2 Dealing with input data
			3.2.3 Formatting reports
			3.2.4 Plotting charts
			3.2.5 Project dependencies overview
		3.3 Implementation details
			3.3.1 Describing data
			3.3.2 Plotting charts
			3.3.3 Preparing reports
			3.3.4 Implementing the user interface
			3.3.5 Connecting parts
Part 2: Introduction to application design
	Chapter 4: Haskell development with modules, packages, and projects
		4.1 Organizing Haskell code with modules
			4.1.1 Module structure, imports and exports, and module hierarchy
			4.1.2 Custom Preludes
			4.1.3 Example: containers-mini
		4.2 Understanding Haskell packages
			4.2.1 Packages at the GHC level
			4.2.2 Cabal packages and Hackage
		4.3 Tools for project development
			4.3.1 Dependency management
			4.3.2 Haskell projects as a collection of packages
			4.3.3 Common project management activities and tools
	Chapter 5: Monads as practical functionality providers
		5.1 Basic monads in use: Maybe, Reader, Writer
			5.1.1 Maybe monad as a line saver
			5.1.2 Carrying configuration all over the program with Reader
			5.1.3 Writing logs via Writer
		5.2 Maintaining state via the State monad
			5.2.1 Basic examples with the State monad
			5.2.2 Parsing arithmetic expressions with State
			5.2.3 RWS monad to rule them all: The game of dice
		5.3 Other approaches to mutability
			5.3.1 Mutable references in the IO monad
			5.3.2 Mutable references in the ST monad
	Chapter 6: Structuring programs with monad transformers
		6.1 The problem of combining monads
			6.1.1 Evaluating expressions in reverse Polish notation
			6.1.2 Introducing monad transformers and monad stacks
		6.2 IO-based monad transformer stacks
			6.2.1 Describing a monad stack
			6.2.2 Exploiting monad stack functionality
			6.2.3 Running an application
			6.2.4 Can we do it without RWST?
		6.3 What is a monad transformer?
			6.3.1 Step 0: Defining a type for a transformer
			6.3.2 Step 1: Turning a monad stack into a monad
			6.3.3 Step 2: Implementing the full monad stack functionality
			6.3.4 Step 3: Supplying additional functionality
			6.3.5 Using a transformer
		6.4 Monad transformers in the Haskell libraries
			6.4.1 Identity is where it all starts
			6.4.2 An overview of the most common monad transformers
Part 3: Quality assurance
	Chapter 7: Error handling and logging
		7.1 Overview of error-handling mechanisms in Haskell
			7.1.1 The idea of exceptions
			7.1.2 To use or not to use?
			7.1.3 Programmable exceptions vs. GHC runtime exceptions
		7.2 Programmable exceptions in monad stacks
			7.2.1 The ExceptT monad transformer
			7.2.2 Example: Evaluating RPN expressions
		7.3 GHC runtime exceptions
			7.3.1 An idea of extensible exceptions
			7.3.2 Throwing exceptions
			7.3.3 Catching exceptions
		7.4 Example: Accessing web APIs and GHC exceptions
			7.4.1 Application components
			7.4.2 Exception-handling strategies
		7.5 Logging
			7.5.1 An overview of the monad-logger library
			7.5.2 Introducing logging with monad-logger into the suntimes project
	Chapter 8: Writing tests
		8.1 Setting a scene: IPv4 filtering application
			8.1.1 Development process overview
			8.1.2 Initial implementation
		8.2 Testing the IPv4 filtering application
			8.2.1 Overview of approaches to testing
			8.2.2 Testing Cabal projects with tasty
			8.2.3 Specifications writing and checking with Hspec
			8.2.4 Property-based testing with Hedgehog
			8.2.5 Golden tests with tasty-golden
		8.3 Other approaches to testing
			8.3.1 Testing functions à la the REPL with doctest
			8.3.2 Lightweight verification with LiquidHaskell
			8.3.3 Code quality with hlint
	Chapter 9: Haskell data and code at run time
		9.1 A mental model for Haskell memory usage at run time
			9.1.1 General memory structure and closures
			9.1.2 Primitive unboxed data types
			9.1.3 Representing data and code in memory with closures
			9.1.4 A detour: Lifted types and the concept of strictness
		9.2 Control over evaluation and memory usage
			9.2.1 Controlling strictness and laziness
			9.2.2 Defining data types with unboxed values
		9.3 Exploring compiler optimizations by example
			9.3.1 Optimizing code manually
			9.3.2 Looking at GHC Core
	Chapter 10: Benchmarking and profiling
		10.1 Benchmarking functions with criterion
			10.1.1 Benchmarking implementations of a simple function
			10.1.2 Benchmarking an IPv4 filtering application
		10.2 Profiling execution time and memory usage
			10.2.1 Simulating iplookup usage in the real world
			10.2.2 Analyzing execution time and memory allocation
			10.2.3 Analyzing memory usage
		10.3 Tuning performance of the IPv4 filtering application
			10.3.1 Choosing the right data structure
			10.3.2 Squeezing parseIP performance
Part 4: Advanced Haskell
	Chapter 11: Type system advances
		11.1 Haskell types 101
			11.1.1 Terms, types, and kinds
			11.1.2 Delivering information with types
			11.1.3 Type operators
		11.2 Data kinds and type-level literals
			11.2.1 Promoting types to kinds and values to types
			11.2.2 Type-level literals
		11.3 Computations over types with type families
			11.3.1 Open and closed type synonym families
			11.3.2 Example: Avoid character escaping in GHCi
			11.3.3 Data families
			11.3.4 Associated families
		11.4 Generalized algebraic data types
			11.4.1 Example: Representing dynamically typed values with GADTs
			11.4.2 Example: Representing arithmetic expressions with GADTs
		11.5 Arbitrary-rank polymorphism
			11.5.1 The meaning
			11.5.2 Use cases
		11.6 Advice on dealing with type errors
			11.6.1 Be explicit about types
			11.6.2 Ask the compiler
			11.6.3 Saying more about errors
	Chapter 12: Metaprogramming in Haskell
		12.1 Deriving instances
			12.1.1 Basic deriving strategies
			12.1.2 The problem of type safety and generalized newtype deriving
			12.1.3 Deriving by an example with DerivingVia
		12.2 Data-type-generic programming
			12.2.1 Generic data-type representation
			12.2.2 Example: Generating SQL queries
		12.3 Template Haskell and quasiquotes
			12.3.1 A tutorial on Template Haskell
			12.3.2 Example: Generating remote function calls
	Chapter 13: More about types
		13.1 Types for specifying a web API
			13.1.1 Implementing a web API from scratch
			13.1.2 Implementing a web service with servant
		13.2 Toward dependent types with singletons
			13.2.1 Safety in Haskell programs
			13.2.2 Example: Unsafe interface for elevators
			13.2.3 Dependent types and substituting them with singletons
			13.2.4 Example: Safe interface for elevators
Part 5: Haskell toolkit
	Chapter 14: Data-processing pipelines
		14.1 Streaming data
			14.1.1 General components and naive implementation
			14.1.2 The streaming package
		14.2 Approaching an implementation of pipeline stages
			14.2.1 Reading and writing data efficiently
			14.2.2 Parsing data with parser combinators
			14.2.3 Accessing data with lenses
		14.3 Example: Processing COVID-19 data
			14.3.1 The task
			14.3.2 Processing data
			14.3.3 Organizing the pipeline
	Chapter 15: Working with relational databases
		15.1 Setting up an example
			15.1.1 Sample database
			15.1.2 Sample queries
			15.1.3 Data representation in Haskell
		15.2 Haskell database connectivity
			15.2.1 Connecting to a database
			15.2.2 Relating Haskell data types to database types
			15.2.3 Constructing and executing SELECT queries
			15.2.4 Manipulating data in a database
			15.2.5 Solving tasks by issuing many queries
		15.3 The postgresql-simple library
			15.3.1 Connecting to a database
			15.3.2 Relating Haskell data types to database types
			15.3.3 Executing queries
		15.4 The hasql ecosystem
			15.4.1 Structuring programs with hasql
			15.4.2 Constructing type-safe SQL statements
			15.4.3 Implementing database sessions
			15.4.4 Running database sessions
			15.4.5 The need for low-level operations and decoding data manually
		15.5 Generating SQL with opaleye
			15.5.1 Structuring programs with opaleye
			15.5.2 Describing database tables and their fields
			15.5.3 Writing queries
			15.5.4 Running queries
	Chapter 16: Concurrency
		16.1 Running computations concurrently
			16.1.1 An implementation of concurrency in GHC
			16.1.2 Low-level concurrency with threads
			16.1.3 High-level concurrency with the async package
		16.2 Synchronization and communication
			16.2.1 Synchronized mutable variables and channels
			16.2.2 Software transactional memory (STM)
appendix: Further reading
	Books
	Research papers
index
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