C++ 入门(第 5 版)；第 19 章 - 算法:std::lower_bound

Question

这是来自 C++ Primer(第 5 版)；第 19 章“附录:算法”:

lower_bound(beg, end, val)
lower_bound(beg, end, val, comp)

Returns an iterator denoting the first element such that val is not less than that element, or end if no such element exists.

upper_bound(beg, end, val)
upper_bound(beg, end, val, comp)

Returns an iterator denoting the first element

但我认为lower_bound返回一个迭代器，表示输入序列中不小于 val 的第一个元素(大于或等于 val)而不是相反(“...第一个元素使得 val 不小于该元素”)。是不是书上写错了？

Answer 1

Is it a mistake in the book?

如果您信任 cppreference ，然后: 是的，这是一个错误:

std::lower_bound

Returns an iterator pointing to the first element in the range [first, last) that is not less than (i.e. greater or equal to) value, or last if no such element is found.

或者，如果您不信任该网站，this Draft C++17 Standard已:

28.7.3.1 lower_bound       [lower.bound]

…

²     Returns: The furthermost iterator i in the range [first, last] such that for every iterator j in the range [first, i) the following corresponding conditions hold: *j < value or comp(*j, value) != false.

在 this (later) online Draft Standard ，是第 25.8.4.2 节 .