Metaprogramming in Prolog

Have you ever felt "stuck" in Prolog? Maybe you've mastered the basics, but your programs have become repetitive, or you've run into a problem that seems to require a level of abstraction you can't quite reach. When you read about metaprogramming, it might seem like a "dark art"-a set of dangerous, confusing, and "unclean" techniques to be avoided.

This book is here to turn that "magic" into "mastery."

I'll start you with the simple "mechanic" analogy. Most programmers are like mechanics, following a blueprint (your code) to build a car (your process). This book will teach you how to become the "roboticist"-the one who writes programs that analyze, fix, and write new blueprints automatically.

This book is structured as a journey through a series of powerful patterns, each building on the last. You will learn to:

• Master the "Metaprogrammer's Toolbox": Understand the built-in predicates like clause/2, functor/3, arg/3, and call/N that make it all possible.
• Build Your First "Code-Walker": Write a program that can recursively traverse any piece of code to find variables or check for "code smells."
• Handle Dynamic Execution Safely: Learn the patterns (and the critical pitfalls) of call/1, including how to build a secure "Command Dispatcher" or REPL.
• Implement Self-Modifying Code: Use assert/1 and retract/1 for the right reasons, like building a high-speed cache (memoization) or managing program state.
• Write "Source-to-Source" Transformers: Build programs that read a .pl file, transform it, and write a new one-the core pattern for building optimizers and refactoring tools.
• Create Your Own "Language" (DSL): Use term_expansion/2 and goal_expansion/2 to build a Domain-Specific Language, like a simple object system, that compiles itself into efficient Prolog.
• Build a Capstone Project: Combine all these skills to build a "smarter" tracer, a tool that can selectively trace your code, filtering out all the noise.

This book is not for the absolute beginner. It is for you-the intermediate Prolog programmer, the student, the developer, or the hobbyist who has learned the basics and is now asking, "What's next?"

It's for anyone who wants to:

• Build smarter, more abstract tools.
• Write code that is less repetitive.
• Understand how compilers, linters, and advanced DSLs really work.
• Finally "level up" and unlock the full, expressive power of Prolog.

The difference between a good Prolog programmer and a great one is the understanding of metaprogramming. Don't just use the language; it's time to master it.

Stop just writing code. Start building programs that design code.

Add Metaprogramming in Prolog to your cart and start your journey to becoming the architect, not just the mechanic.