It’s possible to write a macro that evaluates to the number of arguments it’s called with. (I couldn’t find a link to the place where I first saw it.) So you could write MAX_OF_N() that would work as you’d like, but you’d still need all the numbered macros up until some limit: #define MAX_OF_1(a) (a) … Read more
Currently this is not supported in stable. However there is a feature in nightly called concat_idents: concat_idents!(my_test_, $id) See Rust docs Issue Update: it seems there aren’t near-term plans to add this into stable releases, see issue.
If you’re using GCC or MSVC, there is __COUNTER__. Other than that, you could do something vomit-worthy, like: #ifndef USED_1 #define USED_1 1 #else #ifndef USED_2 #define USED_2 2 /* many many more */ #endif #endif
In this case you should add a default value for the “macro” parameters. Swift 2.2 and higher func log(message: String, function: String = #function, file: String = #file, line: Int = #line) { print(“Message \”\(message)\” (File: \(file), Function: \(function), Line: \(line))”) } log(“Some message”) Swift 2.1 and lower func log(message: String, function: String = __FUNCTION__, … Read more
To give the short answer, macros are used for defining language syntax extensions to Common Lisp or Domain Specific Languages (DSLs). These languages are embedded right into the existing Lisp code. Now, the DSLs can have syntax similar to Lisp (like Peter Norvig’s Prolog Interpreter for Common Lisp) or completely different (e.g. Infix Notation Math … Read more
It is possible to capture doc comments in macro invocations. It is not widely-known, but Rust documentation is actually represented as a special kind of attribute on an item. For example: /// Some documentation comment pub fn function() {} // is equivalent to #[doc=”Some documentation comment”] pub fn function() {} And it is possible to … Read more
If you are using Rust >= 1.31.0 I would recommend using my paste crate which provides a stable way to create concatenated identifiers in a macro. macro_rules! make_a_struct_and_getters { ($name:ident { $($field:ident),* }) => { // Define the struct. This expands to: // // pub struct S { // a: String, // b: String, // … Read more
Yes however this is only available as a nightly-only experimental API which may be removed. You can pass arbitrary identifier into a macro and yes, you can concatenate identifiers into a new identifier using concat_idents!() macro: #![feature(concat_idents)] macro_rules! test { ($x:ident) => ({ let z = concat_idents!(hello_, $x); z(); }) } fn hello_world() { } … Read more