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#![cfg_attr(not(test), no_std)] //! A macro to define lambda-like macros inline. //! //! Syntax: //! //! `defmac!(` *name* [ *pattern* [, *pattern* ... ]] `=>` *expression* `)` //! //! *name* is the name of the new macro, followed by 0 or more patterns //! separated by comma. A pattern can be just an argument name like `x` //! or a pattern like `ref value`, `(x, y)` etc. Note that there is no comma //! between the name and the first pattern. //! //! # Example //! //! ``` //! #[macro_use] extern crate defmac; //! //! fn main() { //! defmac!(mkvec iter => iter.into_iter().collect::<Vec<_>>()); //! //! let v = mkvec!((0..10).map(|x| x * 2)); //! //! defmac!(repeat ref s, n => (0..n).map(|_| &s[..]).collect::<String>()); //! //! let text = String::from("abc"); //! let s = repeat!(text, 10); //! let t = repeat!("-", s.len()); //! println!("{}", s); //! println!("{}", t); //! //! } //! ``` //! //! Did you know that macros can “capture” variables that they have in scope? //! The capture is by name instead of by reference, so we can use //! defmac where we cannot use closures. See the example below: //! //! ``` //! #[macro_use] extern crate defmac; //! //! fn main() { //! let mut result = Vec::new(); //! let mut sum = 0.; //! let input = "2 2 ^ 7 b ^"; //! //! defmac!(push elem => result.push(elem)); //! defmac!(double => *result.last_mut().unwrap() *= 2); //! //! for ch in input.chars() { //! match ch { //! '^' => double!(), //! '0'...'9' => push!(ch as u32 - '0' as u32), //! 'a'...'z' => push!(ch as u32 - 'a' as u32), //! _ => { } //! } //! } //! //! assert_eq!( //! result, //! vec![2, 4, 7, 2]); //! } //! ``` //! //! ## Rust Version //! //! This crate requires Rust 1.20 or later. /// A macro to define lambda-like macros inline. /// /// Syntax: /// /// `defmac!(` *name* [ *pattern* [, *pattern* ... ]] `=>` *expression* `)` /// /// *name* is the name of the new macro, followed by 0 or more patterns /// separated by comma. A pattern can be just an argument name like `x` /// or a pattern like `ref value`, `(x, y)` etc. /// /// Supports arbitrary many arguments. #[macro_export(local_inner_macros)] macro_rules! defmac { // nest matches final rule (@nest $name:ident ($dol:tt) => ( [$($arg:ident)*] $($result_body:tt)+) ) => { macro_rules! $name { ($($dol $arg : expr), *) => { $($result_body)+ } } }; // nest matches entry point and recursive rule (@nest $name:ident ($dol:tt) => ( [$($arg:ident)*] $($result_body:tt)+ ) $p1:pat $(, $p2:pat)* ) => { // `marg` is a hygienic macro argument name defmac!{@nest $name ($dol) => ( [marg $($arg)*] match {$dol marg} { $p1 => $($result_body)+ } ) $($p2),* } }; // reverse patterns before passing them on to @nest // reverse patterns final rule (@revpats [$($args:tt)*] [$($pr:pat),*]) => { defmac!{@nest $($args)* $($pr),*} }; // reverse patterns entry point and recursive rule (@revpats [$($args:tt)*] [$($pr:pat),*] $p1:pat $(, $p2:pat)*) => { defmac!{@revpats [$($args)*] [$p1 $(, $pr)*] $($p2),*} }; // entry point ($name:ident $($p1:pat),* => $result:expr) => { defmac!{@revpats [$name ($) => ([] $result)] [] $($p1),*} }; } #[cfg(test)] mod tests { #[test] fn it_works() { let value = "xyz"; defmac!(none => value); assert_eq!(none!(), "xyz"); defmac!(one x => x); assert_eq!(one!(2), 2); defmac!(two x, y => x + y); assert_eq!(two!(1., 2.), 3.); defmac!(three x, y, z => (x, y, z)); assert_eq!(three!(1, (2, 3), (4, 5, 6)), (1, (2, 3), (4, 5, 6))); defmac!(four w, x, y, z => (w + x, z, y)); assert_eq!(four!(3, 4, "a", "b"), (7, "b", "a")); defmac!(many a, b, c, d, e, f, g, h, i, j, k => (a, b + c, d + e + f, g + h + i + j + k)); assert_eq!(many!(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11), (1, 5, 15, 45)); } #[test] fn eval_order() { use std::cell::Cell; let v = Cell::new(0); let f = || { let n = v.get(); v.set(n + 1); n }; defmac!(two x, y => (x, y)); let result = two!(f(), f()); assert_eq!(result, (0, 1)); assert_eq!(f(), 2); } // Test expansion at module level defmac! { triple value => [value; 3] } #[test] fn module_macro() { assert_eq!(triple!(3), [3, 3, 3]); } }