std :: string :: substr成员函数的复杂性是什么? [英] What is the complexity of std::string::substr member function?

问题描述

std :: string :: substr 成员函数的复杂性是什么?是由标准定义还是由实现定义?

What is the complexity of std::string::substr member function? Is it defined by standard or implementation-defined?

推荐答案

这是标准所要说明的所有内容:

This is all that standard has to say about it:

n3242，21.4.7.8

n3242, 21.4.7.8

1. 要求: pos< = size()
2. 抛出:如果 pos>超出范围，则为 out_of_range .size()
3. 效果:确定要复制的字符串的有效长度 rlen ，以较小者为准 n 和 size()-pos
4. 返回: basic_string< charT，traits，Allocator>(data()+ pos，rlen).

1. Requires: pos <= size()
2. Throws: out_of_range if pos > size()
3. Effects: Determines the effective length rlen of the string to copy as the smaller of n and size() - pos
4. Returns: basic_string<charT,traits,Allocator>(data()+pos,rlen).

因此答案是否定的，复杂性未定义.

So the answer would be no, the complexity is not defined.

已按照n3242进行了更正，位置>大小而不是位置> =大小

Corrected as per n3242, pos > size not pos >= size

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