Functional Programming in C#
Functional Programming in C#
with Categories
About the Book
Note: This is not an Introductory book in C#. The reader must have at least a couple of years of C# experience. Please read the Sample pdf to get an idea about the content of the book.
This book contains the full content of the book "Practical functional C#" Don't buy both books.
This book is focused on the practical use of language-ext functional library in C#. We will break down the Sample projects and see where functional programming fits in modern Web Application development using Asp.Net Core and Domain Driven Design .
The paperback is also Available at Amazon Functional Programming in C#
Book Description
This book goes beyond the introductory ideas of functional programming, while progressively building on practical examples in a comprehensive manner.
Each example is accompanied by online autonomous NET Fiddles :
[https://dotnetfiddle.net/Authors/127896]
[https://dotnetfiddle.net/Authors/120678/dimitrispapadim]
which you can run fork and modify, in order to deepen your understanding of each section.
GitHub repositories
[FunctionalCSharpWithCategories]
[https://github.com/dimitris-papadimitriou-chr/Practical-Functional-CSharp]
By the end of this book, you will have a deep understanding of the ideas behind functional C# that will allow you to program in a functional style with confidence. Also, you will have an overview of how famous functional libraries have implemented different functional concepts.
What you will learn:
- Go beyond the List.Select by understanding how to generalize the idea of map to Functors like Maybe, Either and Task<T>, etc.
- Go beyond the idea of List.Aggregate by understanding the concepts of fold and catamorphism over data structures.
- Learn how to combine functional ideas in order to solve practical problems.
- Use Monads like Maybe, Either, IO, and Task to chain computations.
- Get a deep understanding of recursive methods and learn how to define recursive methods on algebraic data structures.
About the Author
Table of Contents
-
1 Language Functional support
- 1.1 Pure functions and Side effects ... 8
- 1.2 Evolution of Delegates in C# ... 11
- 1.3 Named parameters and Tuples ... 14
- 1.3.1 Lambda expressions and tuples ... 16
- 1.4 Extension Methods ... 18
- 1.5 Using static directive ... 19
- 1.6 LINQ support for custom Data structures ... 20
- 1.7 Currying and partial application ... 21
-
2 Algebras of Programming
- 2.1 Categories ... 24
- 2.2 Monoids ... 26
- 2.2.1 Folding monoids ... 28
- 2.2.2 Monoid homomorphisms and Parallelism ... 30
-
3 Algebraic Data Types
- 3.1 The product structure: ... 35
- 3.1.1 Introduction / Elimination ... 36
- 3.2 The Co-Product (aka Union) structure ... 37
- 3.2.1 Introduction / Elimination ... 39
- 3.3 Extending Union Types ... 39
- 3.3.1 Adding Pattern Matching extensions to Union Types ... 40
- 3.3.2 Rewriting Union Type methods with MatchWith ... 40
- 3.3.3 The C#8.0 Pattern matching Feature ... 41
- 3.4 One ... 42
- 3.5 Recursive Algebraic Types ... 43
- 3.5.1 Rewriting Map with MatchWith ... 44
- 3.5.2 On the value of the symbolic representation ... 45
- 3.5.3 Adding Pattern Matching extension to Native List ... 45
-
4 Functors
- 4.1 The Identity Functor ... 49
- 4.2 Commutative Diagrams ... 51
- 4.3 The Functor Laws ... 51
- 4.4 Pattern Matching ... 53
- 4.5 Id Functor on the Fly ... 57
- 4.5.1 Some more Isomorphisms ... 58
- 4.5.2 The Basic Functor Mechanics ... 60
- 4.6 Extending Task to Functor ... 60
- 4.7 IO Functor, a Lazy Id Functor ... 62
- 4.7.1 Func Delegates as Functor ... 63
- 4.7.2 IO Functor ... 63
- 4.8 Reader Functor ... 64
- 4.9 LINQ Native Query syntax: Functor Support ... 65
- 4.10 Maybe Functor aka Option ... 66
- 4.10.1 Dealing with null ... 66
- 4.10.2 The Null Object Design pattern ... 67
- 4.10.3 The Functional equivalent - Maybe as Functor ... 68
- 4.10.4 Maybe Functor Example ... 71
- 4.10.5 Maybe in Language-ext / Option ... 72
- 4.10.6 Maybe Functor Example With language-ext Option ... 72
- 4.10.7 C# 8. pattern matching Support for Option ... 73
- 4.10.8 Folding Maybe ... 74
- 4.10.9 Using the Linq syntax ... 74
- 4.11 Either Functor ... 75
- 4.11.1 Pattern matching for Either ... 76
- 4.11.2 Using C# 8.0 pattern matching ... 77
- 4.11.3 Either Functor Example ... 77
- 4.11.4 C# 8. pattern matching Support for language-ext Either ... 79
- 4.11.5 Using Either for exception handling ... 79
- 4.12 Explicitly Compositing Functor ... 82
- 4.13 Combining Task and Option – Task> ... 84
- 4.14 Combining Task and Option – OptionAsync ... 86
- 4.15 Combining Task and Either – Task> ... 87
- 4.16 Combining Task and Either – EitherAsync<> ... 89
- 4.17 Functors from Algebraic Data Types ... 90
- 4.18 Applicative Functors ... 93
- 4.19 Reader Applicative Functor ... 94
-
5 Monads
- 5.1 The List Monad ... 100
- 5.2 The Identity Monad ... 101
- 5.2.1 Monad laws for Identity Monad ... 101
- 5.3 Maybe Monad ... 102
- 5.3.1 Using language-ext Option ... 104
- 5.3.2 Using the LINQ syntax with Option Monad ... 105
- 5.4 Either Monad ... 106
- 5.4.1 Using Either Monad for exception handling ... 107
- 5.4.2 Using language-ext Either<> ... 108
- 5.4.3 Using the LINQ syntax with Either Monad ... 109
- 5.4.4 Using Either for Validation ... 109
- 5.5 Validation Monad ... 110
- 5.5.1 Using Validation.Apply to Collect validations ... 111
- 5.6 Task as Monad ... 112
- 5.7 The Task - Option Monad Combination -Task> ... 113
- 5.8 The Task - Option Monad Combination -OptionAsync<> ... 115
- 5.9 The Task - Either Monad Combination -Task> ... 117
- 5.10 The Task - Either Monad Combination -EitherAsync<> ... 119
-
6 Catamorphisms Again
- 6.1 A brief mentioning of F-algebras ... 121
- 6.2 Catamorphisms ... 122
- 6.3 Initial algebra ... 123
- 6.3.1 F-Algebras Homomorhisms ... 124
- 6.4 Catamorphisms for Trees ... 125
- 6.5 Catamorphisms with the Visitor Design pattern ... 127
- 6.5.1 The Base Functor of the List ... 128
- 6.5.2 A brief mentioning of Anamorhisms ... 131
- 6.5.3 F-Coalgebra ... 133
- 6.5.4 Corecursion ... 133
- 6.5.5 A brief mentioning of Hylomorphisms ... 134
- 6.5.6 Hylomorphism example: Mergesort ... 136
- 6.6 Fold’s relation to Cata ... 137
-
7 Traversable
- 7.1 Traversable Array with Either applicative for validation ... 141
- 7.2 Traversable Algebraic data structures ... 142
- 7.3 Traversing with The Task aka Parallel ... 143
- 7.4 Applicative Reader Isomorphism with the Interpreter Design pattern ... 145
- 7.4.1 Standard Catamorphism implementation ... 146
- 7.4.2 Reader applicative implementation ... 147
- 7.4.3 Object Oriented Interpreter Pattern implementation ... 148
- 7.5 Explicitly Composing Traversables ... 149
- 7.6 Foldable ... 150
- 7.6.1 FoldMap ... 151
- 7.6.2 Explicitly Composing Foldables ... 153
-
8 A Clean Functional Architecture Example
- 8.1 Download and Setup the Project ... 154
- 8.1.1 Clean Architecture with .NET core ... 155
- 8.2 A Functional Applications Architecture ... 157
- 8.3 The Contoso Clean Architecture with .NET core and language-ext ... 158
- 8.4 Web Api ... 159
- 8.5 Domain Model ... 161
- 8.5.1 Repositories ... 164
- 8.6 CQRS ... 164
- 8.7 CQRS and MediatR ... 166
- 8.7.1 The Command Pattern with a Mediator ... 166
- 8.7.2 Query Workflow ... 169
- 8.7.3 Command Workflow ... 173
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