macro

Declares a function-style macro: macro name(Expr a, …) -> Code { … }, used as name!(…).

It runs at compile time with the call’s arguments as unevaluated Expr values and returns code that replaces the call: an expression, statements, or declarations depending on where the call is. A last Vec<Expr> parameter takes the remaining arguments. Contextual: use macro::{…} names the macro model module.

use macro::{Expr, Code};

/// `square!(e)` expands to `e * e`.
macro square(Expr e) -> Code {
    return quote expr { ${e} * ${e} };
}

See also#

• Vec
• fn: Declares a function, a method, or (written in an expression) an anonymous function.
• let: Declares a mutable local variable.
• const: Declares a binding that cannot be reassigned: a local, a module constant, or a class field that is set only by new.
• static: Declares a module-level or class-level slot shared by the whole program, or a method without self.
• readonly: A read-only view of a value: nothing reachable through it can be changed.
• if: Runs a block when a bool condition is true.
• else: Introduces the branch of an if that runs when its condition is false (or its pattern does not match).