Do I need to call unlock() at the end of the loop (for a local unique_lock)?

Question

Is this:

std::mutex mutex;
for () {
    std::unique_lock<mutex> lock(mutex);
    // do something
    lock.unlock();
}

Equivalent to this in terms of releasing and acquiring the lock every iteration of the for loop?

std::mutex mutex;
for () {
    std::unique_lock<mutex> lock(mutex);
    // do something
}

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