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

Question

本文来自C++ Primer（第5^th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 returns一个迭代器表示输入序列中第一个元素不小于val（大于或等于val）而不是相反（ “...第一个元素 val 不小于该元素”）。是书上写错了吗？

Answer 1

Is it a mistake in the book?

如果您信任cppreference，那么：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有：

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 中，它是 §25.8.4.2。