c ++是一个空白独立的语言，规则的例外 [英] c++ is a white space independent language, exception to the rule

问题描述

此wikepedia页面将c ++定义为与空白无关的语言。虽然大多数情况下与所有语言一样，规则有例外。我现在唯一能想到的就是这样：

This wikepedia page defines c++ as a "white space independent language". While mostly true as with all languages there are exceptions to the rule. The only one I can think of at the moment is this:

vector<vector<double> >

必须有空格，否则编译器会将>>解释为流运算符。什么其他的。编译一个异常列表很有趣。

Must have a space otherwise the compiler interprets the >> as a stream operator. What other ones are around. It would be interesting to compile a list of the exceptions.

推荐答案

遵循这个逻辑，您可以使用任何两个字符的词法来生成这种规则的例外。例如， + = 和 + = 会有不同的解释。我不会称他们为例外。在C ++中，在许多上下文中，没有空间与一个或多个空间完全不同。当有人说C ++是与空间无关的，它们通常意味着C ++中的一个空格通常与多个空格相同。

Following that logic, you can use any two-character lexeme to produce such "exceptions" to the rule. For example, += and + = would be interpreted differently. I wouldn't call them exceptions though. In C++ in many contexts "no space at all" is quite different from "one or more spaces". When someone says that C++ is space-independent they usually mean that "one space" in C++ is typically the same as "more than one space".

该语言规范规定（参见2.1 / 1），在翻译的第3阶段，允许实现用一个空格字符替换多个空格字符的序列。

This is reflected in the language specification, which states (see 2.1/1) that at phase 3 of translation the implementation is allowed to replace sequences of multiple whitespace characters with one space character.

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