Pragmatic Type-Level Design (PTLD E-Book)
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Pragmatic Type-Level Design

Practical introduction into type-level programming: design principles, design patterns, methodologies, approaches

About the Book

Pragmatic Type-Level Design is a book about programming in types, about the discipline of Software Design, lifted onto the level of types, and about type-level approaches useful in real practice.

This is my second fundamental book about Software Design (but not only), in addition to Functional Design and Architecture.

My goal is to provide a well-written and well-structured source of knowledge about type-level design. I’m not only talking about type-level features but providing a reasoning framework for making the narrative complete and comprehensive. The central philosophy of this book - pragmatism - is used to build a practice-first methodology on how to approach types and not drown in the related complexity. The type-level design is difficult on its own, type-level Haskell features are difficult as well, and there is no need in raising the learning bar even more.

The book will be useful for developers who want to start doing real things on the type level.


If you liked my FDaA book, you’ll find PTLD quite enlightening and complementary to it.

Book completion estimation: end of 2025

Book topics:

type-level design

type-level eDSLs

complexity of solutions

type-level Haskell features

Inversion of Control and Dependency Injection

domain modeling

type-level functional interfaces

design of business logic

interaction with impure subsystems


GitHub repo: Pragmatic-Type-Level-Design

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  • Categories

    • Software Engineering
    • Haskell
    • Functional Programming
    • Software Architecture
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About the Author

Alexander Granin
Alexander Granin

International speaker, researcher, author

Expert Haskell and C++ developer

Software architect, team lead

Haskell consultant

Author of the book "Functional Design and Architecture"

Table of Contents

  • Part I The basics of type-level software design
    • 1 Emergent type-level design
      • 1.1 Approaching the type-level design
        • 1.1.1 Types and values
        • 1.1.2 Pragmatic Type-Level Design
        • 1.1.3 Typed Forms diagrams
      • 1.2 The foreshadowing of type-level design
        • 1.2.1 Basics of generics
        • 1.2.2 Basics of type classes
        • 1.2.3 Design principles
        • 1.2.3 Basics of type-level literals
      • 1.3 Summary
    • 2 Use case: simple extensibility
      • 2.1 Extensibility
        • 2.1.1 Extensibility mechanisms
        • 2.1.2 Extensibility requirement
        • 2.1.3 Extension points
      • 2.2 Basically extensible application
        • 2.2.1 Type class interface
        • 2.2.2 Heterogeneous storage problem
        • 2.2.3 Valuefication and existentification
        • 2.2.4 Valuefied storage
        • 2.2.5 Existentified storage
      • 2.3 Summary
  • Part II Advanced extensibility (TODO)

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