What does auto_ptr::reset mean?

According to reference, the member function evaluates the expression delete myptr, but only if the stored pointer value myptr changes as a result of function call. It then replaces the stored pointer with ptr.

But I still don't get it. Does it mean this member function deletes current myptr and points to another memory space?

Say

Code:

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std::auto_ptr<int> p (new int(100));
p.reset(new int(200));

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Will the memory of new int(100) be freed after that?

Quote:

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Does it mean this member function deletes current myptr and points to another memory space?

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Yes, assuming by myptr you mean the pointer pointing to the int with the value of 100.

Code:

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int* my100ptr = new int(100);
int* my200ptr = new int(200);

std::auto_ptr<int> ap(my100ptr);

ap.reset(my100ptr); // delete is not called.

ap.reset(my200ptr); // delete is called on my100ptr.

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