std::any_of 使用方法

`std::any_of()` 是一个标准库函数，可以用于判断一个范围内的元素是否满足某个特定的条件。它的使用方法如下：

#include <algorithm>
#include <vector>

bool_even(int i) {
    return i % 2 == 0;
}

int main() {
    std::vector<int> v = {1, 3, 5, 6, 7, 9};
    bool any_even = std::any_of(v.begin(), v.end(), is_even);
    // 判断是否有偶数
    return 0;
}

以上代码中，`std::any_of()` 函数接受三个参数：范围的开始迭代器、范围的结束迭代器和一个可调用对象，可调用对象用于判断每个元素是否满足某个条件。在上面的例子中，我们定义了一个 `is_even()` 函数来判断一个整数是否为偶数，并将其作为 `std::any_of()` 函数的可调用对象。

`std::any_of()` 函数会遍历整个范围，对每个元素调用可调用对象，如果任何一个元素满足条件，函数就会返回 `true`，否则返回 `false`。

在以上例子中，我们使用 `std::any_of()` 函数判断了一个整数向量中是否有偶数。如果存在偶数，函数返回 `true`，否则返回 `false`。

相关问题

terminate called after throwing an instance of 'std::bad_array_new_length' what(): std::bad_array_new_length

This error message indicates that an exception of type 'std::bad_array_new_length' was thrown during the execution of the program. This exception is typically thrown when an attempt is made to allocate an array with a negative size or a size that exceeds the implementation-defined maximum size.

To fix this error, you should check your code for any instances where you are attempting to allocate an array with a negative or overly large size. You may need to revise your code to ensure that the array size is always within the valid range.

libc++abi: terminating with uncaught exception of type std::__1::system_error: condition_variable wait failed: Invalid argument

This error occurs when a condition_variable is waiting for a notification, but the underlying condition is not valid. This can happen if the function is called with an invalid argument or if the condition was not initialized properly.

To fix this error, you need to check the arguments being passed to the condition_variable and ensure that they are valid. You may also need to initialize the condition properly before using it.

Here's an example of how to use a condition_variable:

#include <iostream>
#include <condition_variable>
#include <mutex>
#include <thread>

std::condition_variable cv;
std::mutex mtx;
bool ready = false;

void thread_func()
{
    std::unique_lock<std::mutex> lock(mtx);
    ready = true;
    cv.notify_one();
}

int main()
{
    std::thread t(thread_func);

    std::unique_lock<std::mutex> lock(mtx);
    while (!ready) {
        cv.wait(lock);
    }

    t.join();
    return 0;
}

In this example, we create a condition_variable named `cv`, a mutex named `mtx`, and a boolean flag called `ready`. We start a new thread that sets the `ready` flag to true and notifies the condition_variable. In the main thread, we wait for the notification by calling `cv.wait(lock)` in a loop.

Note that we need to acquire the lock before calling `cv.wait()` or `cv.notify_one()`. This ensures that the condition is modified atomically and prevents race conditions.

If you are still experiencing the error after checking your code, you may need to consult the documentation for the specific function that is throwing the exception to see if there are any known issues or limitations.