C语言中的Trigraph sequences

最新推荐文章于 2020-04-12 08:37:49 发布

softwareren1

最新推荐文章于 2020-04-12 08:37:49 发布

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分类专栏：点滴积累文章标签： Trigraph sequences 三字母词

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本文介绍了ANSI C标准中鲜为人知的Trigraph序列概念及其实现细节，详细列举了所有有效的Trigraph序列及其对应的字符替换规则，并通过示例展示了如何进行Trigraph序列的替换。

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以下对Trigraph sequences的描述摘自ANSI C标准，一般很少提到和用到。

2.2.1.1 Trigraph sequences

All occurrences in a source file of the following sequences of
three characters (called trigraph sequences /5/)are replaced with the
corresponding single character.

         ??=      #
         ??(      [
         ??/      \
         ??)      ]
         ??'      ^
         ??<      {
         ??!      |
         ??>      }
         ??-      ~

No other trigraph sequences exist. Each ? that does not begin one of
the trigraphs listed above is not changed.

Example

The following source line

printf("Eh???/n");

becomes (after replacement of the trigraph sequence ??/ )

printf("Eh?\n");