为什么标准库有find和find_if？ [英] Why does the standard library have find and find_if?

问题描述

无法 find_if 只是重载 find ？这是 std :: binary_search 和朋友做的方法

Couldn't find_if just be an overload of find? That's how std::binary_search and friends do it...

推荐答案

考虑 find_if 已重命名为 find ，则您有：

Consider find_if is renamed find, then you have:

template <typename InputIterator, typename T>
InputIterator find(InputIterator first, InputIterator last, const T& value);

template <typename InputIterator, typename Predicate>
InputIterator find(InputIterator first, InputIterator last, Predicate pred);

接下来应该做什么：

find(c.begin(), c.end(), x); // am I finding x, or using x to find?

而不是试图提出一些复杂的解决方案来区分基于 x

Rather than try to come up with some convoluted solution to differentiate based on x (which can't always be done*), it's easier just to separate them.

*这将是不明确的，无论你是什么方案是或它有多么强大†：

*This would be ambiguous, no matter what your scheme is or how powerful it might be†:

struct foo
{
    template <typename T>
    bool operator()(const T&);
};

bool operator==(const foo&, const foo&);

std::vector<foo> v = /* ... */;
foo f = /* ... */; 

// f can be used both as a value and as a predicate
find(v.begin(), v.end(), f); 

†保存心态阅读。

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