什么是 C 中的指定初始值设定项? [英] What is a designated initializer in C?

问题描述

我知道这可能是一个基本问题.

I know this might be a basic question.

我有一项任务要求我了解 C 中的指定初始值设定项是什么以及用 1 来初始化变量意味着什么.

I have an assignment that requires me to understand what a Designated initializers in C are and what it means to initialize a variable with one.

我不熟悉这个术语，也找不到任何决定性的定义.

I am not familiar with the term and couldn't find any conclusive definitions.

什么是 C 中的指定初始值设定项?

推荐答案

指定的初始化器有两种风格:

Designated initialisers come in two flavours:

1) 它提供了一种初始化数组中特定元素的快速方法:

1) It provides a quick way of initialising specific elements in an array:

int foo[10] = { [3] = 1, [5] = 2 };

会将所有元素设置为 foo 为 0，除了索引 3 将设置为 1 和索引 5 将设置为 2.

will set all elements to foo to 0, other than index 3 which will be set to 1 and index 5 which will be set to 2.

2) 它提供了一种显式初始化 struct 成员的方法.例如，对于

2) It provides a way of explicitly initialising struct members. For example, for

struct Foo { int a, b; };

你可以写

struct Foo foo { .a = 1, .b = 2 };

请注意，在这种情况下，未明确初始化的成员将被初始化，就像实例具有 static 持续时间一样.

Note that in this case, members that are not explicitly initialised are initialised as if the instance had static duration.

<小时>两者都是标准 C，但请注意，C++ 不支持任何一个(因为构造函数可以使用该语言完成这项工作.)

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Both are standard C, but note that C++ does not support either (as constructors can do the job in that language.)

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