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Introduction
Procedural macros in Rust are like tiny bits of code that write other code for you — at compile time. They can be used to build entire functions, types, or even custom mini-languages.
They’re brilliant for:
- Cutting down boilerplate
- Embedding domain-specific languages (DSLs)
- Doing clever things at compile time so runtime doesn’t have to lift a finger
In short: you write code that runs while Rust is compiling, and it inserts new code into your project.
Implementation
Let’s say you want to write maths expressions like this in your code:
math_expr!(3 + x * (2 - y))Instead of manually writing all the parentheses and worrying about precedence, you want Rust to just get on with it.
We’ll build a procedural macro that parses the expression and compiles it directly into native Rust — no interpreters, no slowdowns, just straight to machine code.
First, let’s make a new crate just for our macro (library):
cargo new math_expr_macro --lib…
