SL.io.50: Avoid endl
SL.io.50：避免使用endl
Reason（原因）
The endl manipulator is mostly equivalent to 'n' and "n"; as most commonly used it simply slows down output by doing redundant flush()s. This slowdown can be significant compared to printf-style output.
endl操纵符差不多等于是' n'和“ n”；使用它最常见的结果是通过执行多余的flush（）来减慢输出速度。与printf样式的输出相比，这种速度下降可能会显著。
Example（示例）
代码语言：javascript复制cout << "Hello, World!" << endl; // two output operations and a flush
cout << "Hello, World!n"; // one output operation and no flush
Note（注意）
For cin/cout (and equivalent) interaction, there is no reason to flush; that's done automatically. For writing to a file, there is rarely a need to flush.
对于cin / cout（和等效的）交互，没有理由刷新；那是自动完成的。对于文件写入，几乎不需要刷新。
Note（注意）
Apart from the (occasionally important) issue of performance, the choice between 'n' and endl is almost completely aesthetic.
除了（有时很重要的）性能问题之外，在' n'和endl之间进行选择几乎是完全取决于美感的。
原文链接
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#slio50-avoid-endl
