Macros - Rust for C-Programmers

2.11 Macros

Macros in Rust are more powerful than C preprocessor macros. They perform syntactic transformations on the input code at compile time.

2.11.1 Declarative and Procedural Macros

Declarative (macro_rules!): Pattern-based expansions.
Procedural: Written in Rust, allowing more complex code generation.

macro_rules! say_hello {
    () => {
        println!("Hello!");
    };
}

fn main() {
    say_hello!();
}

2.11.2 The `println!` Macro

println! handles compile-time formatting, making it safer than C's printf (which relies on matching format specifiers to argument types).

2.11.3 Comparison with C

#define SQUARE(x) ((x) * (x))

C macros are text substitutions. Rust macros work with the language's syntax tree, avoiding many pitfalls of textual substitution.