Macros are, in essence, a tool for making the compiler write code for you. You give the compiler a formula for generating code given some input parameters, and the compiler replaces every invocation of the macro with the result of running through the formula. You can think of macros as automatic code substitution where you get to define the rules for the substitution.
Rust’s macros come in many different shapes and sizes to make it easy to implement many different forms of code generation. The two primary types are declarative macros and procedural macros, and we will explore both of them in this chapter. We’ll also look at some ...
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