宏(也称为“声明式宏”或“模式宏”)和过程宏。本文主要是介绍Rust声明式宏的定义和使用,以及一些宏编程基本原理,帮助大家实现Rust宏编程入门。 一、获取关于宏 熟悉C语言的童鞋对宏不会陌生,比如定义一个取最小值的宏,类似这样: #define MIN(a, b) ((a) < (b) ? (a) : (b)) 应用该宏,取两个字...
// demo mutliply(2 + 3, 4 + 5)#define multiply(x, y) x * y// 错误,宏展开: 2 + 3 * 4 + 5,结果19#define multiply(x, y) ((x) * (y))// 正确,红展开: ((2 + 3) * (4 + 5)),结果45 我们来看看Rust版本的宏 macro_rules!multiply{($x:expr,$y:expr)=>{$x*$y};}...
#include<stdio.h>#defineADD(a,b)(a)+(b);intmain(){int a=10;int b=22;int _res=ADD(a,b)_res=ADD(a+1,b)_res=ADD(a*2,b+3)} 这样,我们在使用宏的时候,就避免了意外结果的发生。这样展开之后的代码如下所示: 代码语言:javascript 复制 intmain(){int a=10;int b=22;int _res=(a)...
Fix issue withdefine_label!instantiation in a 3rd party crate (#17958) 10天前 docs-rs Trait tags on docs.rs (#17758) 20天前 docs-template Fix a few typos (#17292) 2个月前 docs Usetarget_abi = "sim"instead ofios_simulatorfeature (#17702) ...
$crate::try_migrate_toml_chain!(error: $err, chain: [$a, $($rest),+]) ); } This works, but is quite verbose. It gets even more verbose with 3 arguments. This leads me to my question. Question Is there an easy(er) to define a macro so the keyword-ish inputs can be position...
To define a lexer, use the lexer! macro.lexer! { fn take_token(tok: 'a) -> Token<'a>;First declare the name of the function, the name of the token you will be able to access within the lexer, and the return type of your lexer. You can also optionally declare a lifetime for ...
具体来说,define_type_foldable_and_lift首先通过宏ast_struct!定义了一系列语法树节点的结构体,这些结构体表示不同的类型和语法结构。然后给每个结构体实现了TypeFoldable的方法。这些方法根据具体的类型组织起来,通过递归调用TypeFoldable的方法实现类型的遍历和转换。
MACRO(i32, std::int32_t) \ MACRO(i64, std::int64_t) \ MACRO(f32, float) \ MACRO(f64, double) #define FOR_EACH_TRIVIAL_STD_VECTOR(MACRO) \ FOR_EACH_NUMERIC(MACRO) \ MACRO(usize, std::size_t) \ MACRO(isize, rust::isize) #...
Determine if a type implements a logical trait expression?, brought to you by@NikolaiVazquez! This library definesimpls!, a macro?that returns aboolindicating whether a type implements a boolean-like expression over a set of traits?. assert!(impls!(String:Clone&!Copy&Send&Sync)); ...
#[macro_use] extern crate native_windows_gui as nwg; use nwg::{Event, Ui, simple_message, fatal_message, dispatch_events}; /// Custom enums are the preferred way to define ui ids. It's clearer and more extensible than any other types (such as &'str). ...