Macros
Declarative macros (macro_rules!), derive macros, attribute macros, procedural macros, macro hygiene
1What is the syntax used to define a declarative macro in Rust?
What is the syntax used to define a declarative macro in Rust?
답변
The macro_rules! syntax is used to define declarative macros in Rust. This form of metaprogramming uses pattern matching on Rust syntax to transform code at compile time. Declarative macros are also called "macros by example" because they work by matching patterns and producing code based on those patterns.
2How to invoke a macro in Rust?
How to invoke a macro in Rust?
답변
Macros in Rust are invoked with an exclamation mark after their name, followed by arguments in parentheses, brackets, or braces. This convention allows to visually distinguish macro calls from normal function calls. For example, println!("Hello") or vec![1, 2, 3] are macro invocations.
3Which fragment specifier to use to capture an expression in a declarative macro?
Which fragment specifier to use to capture an expression in a declarative macro?
답변
The fragment specifier $e:expr captures a Rust expression in a declarative macro. Fragment specifiers define the type of syntax the macro can accept. Other common specifiers include ident for identifiers, ty for types, tt for a token tree, and block for a code block.
What is the main difference between declarative and procedural macros?
What is macro hygiene in Rust?
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