评估声明中部前pression用反斜杠 [英] evaluate expression with backslash in middle of statement

问题描述

假设在C，我有以下的code：

Suppose in C, I have the following code:

i=5 \    
+6;  

如果我打印 I ，它给了我11。

If I print i, it gives me 11.

我不明白上面的code正确执行。乍一看，我猜这是因为无法识别的标记 \\ 的编译器错误。有人能解释什么逻辑？是它最大适合的逻辑关系？

I do not understand how the above code executes correctly. At first glance, I guessed it to be compiler error because of unrecognized token \. Can somebody explain the logic? Is it related to maximal munch logic?

推荐答案

在一行的末尾的反斜线告诉编译器忽略新行字符。

A backslash at the end of a line tells the compiler to ignore the new-line character.

有格式化线是可读的对人类不中断的源文本的一种方法。例如，如果你有引号括起来的长字符串，你可以用一个反斜杠，继​​续在新行字符串不插入字符串中的换行符。

It is a way of formatting lines to be readable for humans without interrupting the source text. E.g., if you have a long string enclosed in quotation marks, you can use a backslash to continue the string on a new line without inserting a new-line character in the string.

（这是比较有用之前C标准补充说，邻近的字符串，例如ABC，高清，被连接的属性。现在你可以将字符串连续行，他们将被连接起来。在这之前，你必须使用反斜杠做到这一点。）

(This was more useful before the C standard added the property that adjacent strings, such as "abc" "def", are concatenated. Now you can put strings on consecutive lines, and they will be concatenated. Prior to that, you had to use the backslash to do it.)

目前反斜杠最常见的用途是作为 heretolearn 指出，要继续preprocessor宏定义。不同于常规的C语句，preprocessor语句必须在同一行。然而，一些preprocessor宏定义是相当长的。要格式化（有点）很好，一个定义是在多个物理线S $ P $垫，但反斜线使得他们在同一行编译器（包括preprocessor）。

Nowadays the most common use of the backslash is, as heretolearn points out, to continue preprocessor macro definitions. Unlike regular C statements, preprocessor statements must be on a single line. However, some preprocessor macro definitions are quite long. To format them (somewhat) nicely, a definition is spread over multiple physical lines, but the backslash makes them into one line for the compiler (including the preprocessor).

一个反斜​​杠后跟一个换行符是的完全由编译器的源文本删除，不像本身就是一个换行符。所以原文：

A backslash followed by a new-line character are completely removed from the source text by the compiler, unlike a new-line character by itself. So the source text:

abc\
def

等同于单一的标识符 ABCDEF ，而不是 ABC DEF 。你可以在不同的字母序列（三字符序列，如 ?? = 任何操作员或其他语言结构的中间使用，转换为替换字符，如＃，反斜线全新的在线处理前）：

is equivalent to the single identifier abcdef, not abc def. You can use it in the middle of any operator or other language construction except trigraph sequences (trigraph sequences, such as ??=, are converted to replacement characters, such as #, before the backslash-new-line processing):

MyStructureVariable-\
>MemberName

IncrementMe+\
+

不过，不这样做。合理地使用它。

However, do not do that. Use it reasonably.

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