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Implements Elixir's |> for Rust as pipe!.
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| /* | |
| * Compile with: | |
| * rustc -Z unstable-options --pretty expanded pipe.rs | |
| */ | |
| /* @file pipe.rs | |
| * @author Jeremy W. Sherman (GitHub: @jeremy-w) | |
| * @license ISC | |
| * | |
| * Implements and demonstrates use of the "pipe" (aka "thread-first") macro. | |
| */ | |
| /* | |
| Copyright (c) 2015, Jeremy W. Sherman | |
| Permission to use, copy, modify, and/or distribute this software for any | |
| purpose with or without fee is hereby granted, provided that the above | |
| copyright notice and this permission notice appear in all copies. | |
| THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH | |
| REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY | |
| AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, | |
| INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM | |
| LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR | |
| OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR | |
| PERFORMANCE OF THIS SOFTWARE. | |
| */ | |
| // trace_macros is behind a feature gate. | |
| // Good luck finding something to explain what that means | |
| // concretely for a newb! | |
| //#![feature(trace_macros)] | |
| /// Directly substitutes in its argument. | |
| /// Somehow avoids an error in the base case of `pipe!`. | |
| macro_rules! result { | |
| ($e:expr) => { $e }; | |
| } | |
| /// Threads an expression as the first argument to the following | |
| /// function. Analogous to Elixir's `|>` and Clojure's `->`. | |
| /// | |
| /// # Examples | |
| /// ``` | |
| /// pipe! { 1 , plus(2) , plus(3) } | |
| /// => thread the 1 into the plus(2) | |
| /// pipe! { plus(1, 2) , plus(3) } | |
| /// => thread the plus(1, 2) into the plus(3) | |
| /// plus( plus(1, 2) , 3 ) | |
| macro_rules! pipe { | |
| ($e:expr, $func:ident ( $($args:tt)* )) => { | |
| /* For whatever reason, when I don't wrap this in result!, | |
| * I get error: | |
| * | |
| * pipe.rs:17:21: 17:26 error: unexpected token: `3` | |
| * pipe.rs:17 $func($e, $($args)*) | |
| * ^~~~~ | |
| */ | |
| result!($func($e, $($args)*)) | |
| }; | |
| ($e:expr, $func:ident ( $($args:tt)* ), $($rest:tt)*) => { | |
| pipe!($func($e, $($args)*), $($rest)*) | |
| }; | |
| } | |
| fn plus(x: i32, y: i32) -> i32 { | |
| return x + y; | |
| } | |
| fn main() { | |
| //trace_macros!(true); | |
| let result = pipe! | |
| { 1 | |
| , plus(2) | |
| , plus(3) | |
| }; | |
| println!("{}", result) | |
| } |
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