C++20 读书笔记（1）

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发布于 2022-10-25 16:53:39

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发布于 2022-10-25 16:53:39

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最近在看C++20相关的内容，本篇记录下遇到的比较好用的特性

Module

C++20新增的4个大特性之一，Module解决的是以前C编译include预处理效率低下痛点。提案地址，具体内容单独介绍，需要了解的事 module，import也成为关键字了，C++20之前的代码最好不要使用，防止冲突。

std::format

推荐的格式化字符串方法

if语句支持初始化变量

C++ allows you to include an initializer inside an if statement using the following syntax:
if (<initializer>; <conditional_expression>) { <if_body>
} else if (<else_if_expression>) { <else_if_body>
} else { <else_body>
}

Three-Way Comparisons

新增的运算符 <=>，结果如下:

strong_ordering::less: First operand less than second
strong_ordering::greater: First operand greater than second
strong_ordering::equal: Equal operands

对于符点:

partial_ordering::less: First operand less than second
partial_ordering::greater: First operand greater than second
partial_ordering::equivalent: Equal operands
partial_ordering::unordered: If one or both of the operands is not-a-number

对于自定义类型，也可以返回以下类型:

weak_ordering::less: First operand less than second 
weak_ordering::greater: First operand greater than second
weak_ordering::equivalent: Equal operands

<compare>也提供了其他的方法可以使用: is_eq(), is_neq(), is_lt(), is_lteq(), is_gt(), and is_gteq()